## Interstellar Ark

Gilgamesh, 14 February 2007 in Philosophy

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The concept of star travel, from planetary system to planetary system, is at the same time completely familiar and completely uncharted. Familiar, as we have certainly all heard of science fiction stories set on a far galaxy, where planets are nations or provinces of an empire. The characters usually move from one planet to another during intervals of time consistent with the story. The actual travel appears just like a formality, which the future advancements of a Triumphant Physics will put within reach.

This is what I’ll call the “strategy zero” (S0) : here travel is “instantaneous” or at the very least quicker than one year, eg. comparable to the durations of terrestrial travels or manned missions to the moon or other solar system’s bodies.

The way toward stars becomes however quite unfamiliar if we consider that such Triumph of Physics could possibly not happen, and that the famous constant of Einstein c, the speed of light (3E8 m/s), represents an horizon speed which is impossible to exceed and which is even extraordinarily difficult to approach, so that we would begin to see outer space like it is seen by astronomers: a vastness compared to which that of terrestrial oceans is nothing.

It is not without reserve that our mind adapts to the true dimensions of interstellar space. The insanity of these distances is not the only reason: in a sense, one could say that the “strategy zero” is enracined in a child’s desire of space. Not of a space-distance, of a horridly naked space, speechless and fearless, but of a space-treasure, and of the worlds which roll within its vastness. All these worlds whose reach should not suffer any delay and whose discovery turns on our imagination.
Realism helping, we leave with some regret the green paradise of “strategy zero”, but we can still consider a little more “teenager” strategy, within the framework of Special Relativity, which we will name “short strategy” or SI, which promises a travel duration within a man’s lifetime.

Short strategy : the relativistic rocket

In SI, which is specifically relativistic, one benefits from the contraction of traveller’s proper time ($\tau$) when its velocity approaches c. If t is the time for a stationary observer,

where $\gamma$ is the Lorentz factor,

When v/c approches one, $\gamma$ tend toward infinite and $\tau$ tend toward zero. In other words, by approaching the speed of light the traveller’s time runs slower and slower so as one light-year may be traversed in less than one year of traveller’s proper time. This is the principle of the relativistic rocket. The only theoretical limit is the acceleration, which should be kept within physiologically acceptable limits for a human, that is to 1 g or 9,81 m/s².1

The table below gives an idea of the travel durations and the reachable distances depending on the v/c ratio, by constraining acceleration to a constant value of 1 g (this constraint is extremely demanding as we will see):

ly = light-years (1 ly ~ 10 000 billions km)
1 g = acceleration of 9,8 m/s per second, measured in the traveller’s reference frame
$\tau$ and t in years, d in light-years, v/c and $\gamma$ dimensionless

Thus, in just 12 years of proper time (but 113 243 years for the stationary observer), which is a long time but still bearable in a comfortable spaceship, one could traverse the whole Galaxy, whose diameter is 100 000 light-years. But this still requires to approach very closely the speed of light. It should also be considered that, if one wants to arrive at destination at zero speed, it is necessary to reverse the direction of thrust at midway in order to slow down; so that the travel duration is appreciably twice longer, which still remains reasonable. The total travel time (proper time of the traveller) to arrive at zero speed on a target located at D years light, while accelerating and decelerating at the constant rate of 1g in its reference frame is:

$\tau$ = 1,94 arccosh (d/1,94 + 1) years

For d = 100 000 ly (Galaxy extent), $\tau$ = 22.4 years. Thus, if we consider travel duration, SI allows to reach targets as remote as wanted within durations not exceeding human lifespan. It is on this basis that we define this strategy : duration of terrestrial travels (1 year) < $\tau$ < human lifespan (less than 100 years).

Energy considerations

The difficulty of SI is about energy. All happens as if one must pay on the side of energy what one did not spend on the side of travel duration. Let us consider the most favorable case. The propulsion is more effective when one ejects behind oneself the lightest possible projectile at the highest possible speed. The absolute optimum is thus reached when all the fuel is converted into photons (zero mass) collimated behind the spaceship. The only reaction allowing 100% conversion of fuel into photons is the reaction matter-antimatter. It would be then needed to collimate the photons in a gamma laser beam (“graser”) in the ideal case. Neither the antimatter fuel, neither its combustion, nor the gamma laser collimation are within reach of our current technology, but this sets the theoretical maximum. The ratio of the total fuel mass (matter + antimatter) M0 on the spaceship mass M is in this case :

with a = 9,8 m.s-2 = 1,02 ly.year-2
c = 3e8 m.s-1 = 1 ly.year-1
$\tau$ in years

To reach the other end of the Galaxy ($\tau$ = 22.4 years) it would be needed to take 10 million tons of fuel for each kilogram of spaceship structure. This is the absolute theoretical minimum, based on a propulsion efficiency of 1 (which cannot never be reached, as the reaction would produce neutrinos carrying part of the impulse in all directions) and which does not take into account the energy costs of the antimatter production. Antimatter must be produced in particle beams accelerated by classical means. For fundamental reasons (conservation of the baryon number), the maximum theoretical conversion rate is 1/2. In practice in current accelerators it is much lower, about 4E-8 (that is, one antiproton produced every 400 million collisions). One can reasonably hope to gain 3 to 4 orders of magnitude but nothing more can be foreseen beyond such technological horizon.

The SI strategy, realistic on the level of travel durations, quickly ceases to be realistic on the level of energy requirements. Of course, when considering the alternate “long” strategy (SII), one should keep in mind that SI-SII form a continuum, and that what is required is to find the intermediate optimum. In particular, the above scenario is a limiting one which would be not considered, as requiring a constant acceleration of 1g throughout the way is an extremely expensive condition in term of fuel consumption.

In a more general case, where a period of non-accelerated flight is allowed before decelerating, and without reaching the limiting case of an ejection of photons, the ratio of the departure mass M0 (structure + fuel) on the arrival mass M (structure alone) is calculated as follows:

$\frac{M_0}{M}= \left[\frac{1+\frac{v}{c}}{1-\frac{v}{c}}\right]^{\Large{{\frac{c}{v_e}}}$

with c the speed of light
v the coasting flight velocity (which is also the maximum velocity)
ve the fuel ejection speed (ve < c)
The above mentioned optimum should mean determining the energy minimum allowing to reach a potential stellar target. Such minimum is determined according to the technological and political level of humanity, and there is of course a possible interaction between the goal and the actors. One can suppose reasonable that the interest expressed by mankind for its galactic environment will imply a "passage to the act" as soon as the energetic barrier problem is considered solved at some point, within the first target falling in range within this barrier. And this, even if the duration of travel is very large. This is because, unlike for the energy barrier which has no maximum, the time barrier has a kind of plateau at some canonical duration which one may set equal to about a century. If a single man is able to consider without regrets to live his whole life in a spaceship on the way towards stars, then time is no longer a barrier and the only constraint is the energy needed to build, drive and maintain the spaceship structure. It is this temporal plateau which makes it possible to lower the energy barrier, and the long strategy is based on a multi-centuries duration.

Scarcity of planetary systems

There is another aspect than energy to take into account, which pertain not to astronautics (rockets, engines…) but to astrophysics and exobiology. It is the planet-target or rather the entire stellar system target, including its small gray bodies (asteroids, comets).

One can only accelerate small structures at relativistic speeds, given the magnitude of the M0/M ratio allowing to reach such speeds. Small structures which should nevertheless accommodate as more human beings as possible, so as to ensure sufficient genetic diversity, that is at least 1,000 people.

It would be possible to lower the structure requirements in the relativistic case by hibernating an appreciable fraction of the occupants.

But this would imply the strong requirement to find a target planet immediately habitable without terraforming.

On at least a few hundreds contiguous km², one should ensure of the following minimal environmental conditions:
- Gravity: 0,5 - 2 g
- Annual amount of radiation: < 100 milliSievert
- Atmospheric pressure: 0,5 and 5 atm
- O2 partial pressure: 0,1 - 0,5 atm
- Temperature : -50 and +50°C
- Presence of water at surface or sub-surface
- Absence of pollutants

To reach Earth’s standards, we should add:
- diversified climatic systems based on the water cycle
- liquid water oceans
- stellar spectrum at ~6000°K
- lenient ecosystem

In addition, planning a short strategy to reach a very distant body implies to reach a target which one knows only remotely. Because if it is question of sending automatic probes to explore the system beforehand, then they should also move at relativistic speeds while the future travellers would be at rest, waiting for information to return by radio transmission. But since the target is located beyond a few light-centuries, the latent period (a millennium for a target located at 500 ly) exceeds the travel duration to a closer system in the long strategy, even if the target is less viable, we will see why.

Concerning the frequency of livable planets in the stellar systems, next decades should bring much information which we await with much impatience. But it does not seem presumptuous to me to predict that this frequency will be found low, when considering the requirements enumerated above. Consequently there could be very little chances to find some in the vicinity, say to less than 20 light-years. The number N of stars located at a distance R from the Sun is:

N = bR3
with:
b ~ 0,017 stars.ly-3 for R<250 ly
R in light-years

The star spectral type (i.e. its surface temperature) should be similar to that of the Sun (G2), which restricts the potential targets to types F, G or K, accounting for approximately 20% of nearby stars. We may add that about half stars belong to a multiple system, which is less likely to host stable planetary orbits.

Let's set to 10% the ratio of FGK systems tolerating the presence of a telluric planet in a stable orbit at the right distance from the star.

Nhab = 0,1 N

That gives a series of sample values for N and Nhab for increasing distances in light-years from the Sun:

We can see for example that if less than 1% of stellar systems include a planet of terrestrial morphology, then there is little chance of finding one at less than 40 light-yearsl.

Even by assuming exponential advances in observational astrophysics, when one can expect that a purely radioelectric observation of a remote system, located at hundreds, thousands or tens of thousands light-years could deliver completely satisfactory information allowing to predict the possibility to colonize it “right from landing”? And this, particularly with regard to its ecosystem. There is undoubtedly not much to fear from the very large (wild animals…) or nano (viruses, requiring compatibility of genetic systems). But mico-organisms of bacterial or fungic type require a simple organic substrate to develop. Such risk remains reasonable, but it counts in the total incurred risk. Everything can happen, and everything should be considered by the travelers, in a much more dramatic way than this reflection may do. A colony reduced to the minimum in a vessel itself minimal, is delivered feet and fists tied to the slightest unforeseen, without hope of any terrestrial help, not even moral. How can one imagine more unforeseen than such a first way out of the solar system? What would happen if the 20 planned years would result in 200 years of confined life?

From this, one may conclude that humankind cannot reasonably venture in the surrounding immense spaces without being rigorously autonomous and detached of any calendar, with the only exception of the energy requirements.

The long strategy aims this autonomy. The energy needed for propulsion at “low” speed (0.015 c) and for the maintenance of a large structure, comparable to a micro-planetary body of gigaton mass, for a duration close to a millennium is comparable with that necessary to the propulsion of a thousand times less massive body at relativistic speed (0.9 c), which supposes ejection of great amounts of fuel at a speed very close to c (say 0.99 c), which is at the borders of our technological horizon. The long strategy constitutes the more “classical” of the solutions, thus the least technologically demanding. S0 strategy is based on theoretical advances, even more than technological ones, located outside of our horizon, and supposing that such solutions do actually exist. It can neither be evaluated nor discussed. SI is based on a well established relativistic physics, but whose practical application demands energy sources which are not available when aiming a very distant target in a lifetime duration. Technologically, it needs to achieve an ejection velocity at the borders of our technological horizon. It also implies a small structure which cannot stand a long term autonomy. SII is both safer and located within our horizon of possibility, even if it is not one of this century.

Long strategy: the Ark

The most effective propulsion which may be achieved within our technological horizon is nuclear fusion. The principle is to confine light nuclei at very high temperature to produce their fusion in a very hot plasma, with electric power allowing ejection of plasma in a magnetic conduit.

This principle would allow to reach ejection velocities of 20,000 km/s. In order to be used as a source of energy, a nuclear fusion reaction must satisfy several criteria. It must:

• be exothermic, which limits reagents to the part of the binding energy curve corresponding to light nuclei, with few protons, making helium-4 (more rarely deuterium and tritium) the headlight reaction product because of its strong binding energy,
• imply nuclei with few protons because of the need to overcome the coulombic repulsion so that nuclei may approach sufficiently to achieve fusion,
• have no more than two reagents: for densities lower than those of stars, the production of three simultaneous collisions is too improbable. It should be noted that in inertial confinement one both exceeds stellar densities and temperatures, which makes it possible to compensate for the weakness of the third parameter of Lawson’s criterion, the very short duration of confinement,
• have at least two products of reactions allowing the simultaneous conservation of energy and impulse,
• conserve at the same time the number of protons and neutrons. Cross sections for the weak interaction being too small, the reaction p + p -> D is unusable, even if it is the one which takes place in the Sun and is constantly flooding us with energy. Proton half-life (the average time needed by a proton to react with another proton to form Deuterium, starting the feedback chain leading to helium-4) under the extreme conditions of temperature and density in the nucleus of a star (density: 150 g/cm3, temperature: 13 millions degrees Kelvin) is about 10 billion years. This as in order to occur, the reaction requires a beta decay, that is the spontaneous conversion of one of the two reactional protons into a neutron (a purely “weak” phenomenon), and this, at the very moment of the interaction p-p.

Nuclei (or isotopes) available for the reactions are:

(01) 1H or p, light hydrogen or proton, the most usual,
(02) 2H or D, heavy hydrogen or deuterium, present in small quantity (0.0015% in terrestrial water that is 15 ppm), and maybe 10 times more in some small bodies of solar system, primarily as heavy water HDO),
(03) 3H or T, tritium, instable, with period 12.3 years, therefore absent in natural materials,
(04) 3He, He3, helium-3 present as a trace in the lunar ground and the atmosphere of giant planets,
(05) 6Li, Li6, lithium-6,
(06) 7Li, Li7, lithium-7,
(07) 11B, B11, boron-11,
the latter 3 elements being present as a trace (estimated 6-7 ppm) in the small bodies of solar system.

The fusion reactions concerning these isotopes are:

n represents neutron (in bold when it can breed deuterium).
1 MeV : 1 million electron-volts (eV). 1 eV = 1,602E-19 Joules

We may distinguish two kinds of reactions:
- those producing neutrons and gamma radiation: (02), (04), (06), (07), (09). The reaction (12) produces a neutron but should be put aside because it is endothermic. However coupling the two ways of Li-7 (11) + (12) is exothermic (balance: +2,2 MeV) and this reactional way could be interesting.
- those which produce only charged nuclei: protons, deutons, alpha particles (4He) : (01), (03), (05), (08), (09), (10) (11), (13), (14), (15).

The reactions of the first kind may seem at first unfavorable, as neutrons and gamma photons are not sensitive to electromagnetic fields, and so cannot be ejected by a conduit: their contribution to propulsion is zero whereas they carry the majority of the impulsion. Moreover they are very aggressive and “activate” the metal structures. On the other hand, the reactive nuclei are relatively abundant: these reactions imply deuterium in (3). The reactions of the second kind are ideal for propulsion but tritium is not naturally available and helium-3, lithium-6-7 and boron-11 are much more rare than deuterium in the small bodies of the solar system. However the required fuel mass is considerable, about 21 Gt (gigaton, 1 Gt = 1 billion tons) on the hypothesis adopted hereafter.

One possibility is to use the neutron produced to breed deuterium in a fertile layer of hydrogen 1H.

The D-D reaction has two equiprobable ways, (2) and (3). In the first, pn+pn produces pnn+p (a tritium nucleus and a proton), in the second ppn + n (a helium-3 nucleus and a neutron). The produced tritium is then likely to react in (5) pnn+pnn -> ppnn + 2n (a helium-4 nucleus and 2 neutrons). The two neutrons produced in this second stage of reaction may in their turn breed deuterium by reacting with the fertile layer of light hydrogen.

The great technical difficulty consists in -amongst other- not “wasting” impulse when passing from the first reactional stage (D-D) to the second (T-T, or He3-He3). The ejection velocity is the key parameter in determining the engine efficiency, and it is primarily allowed by the high temperatures of the reactions products. A proton at 20,000 km/s has a kinetic energy of about 4 MeV, which well represents the magnitude of the reactions described above. The second fusion reaction must thus occur within the jet of plasma. Whatever is the difficulty, a complete breeding (at 1:1 rate), even with a very slight surplus, represents an absolutely crucial factor to judge feasibility. The fusible isotopes are only present at the state of traces in the small bodies. A complete breeding only requires to take on board small initial quantities, since each gram undergoing fusion breeds one gram in the fertile layer. If breeding is only partial, it is needed before departure to distil enormous quantities of hydrogen so as to take on board a fuel already strongly enriched in deuterium or other fusible nuclei. The mass needed to provide fuel vary between 1 to 5000 between the two.

Another concept which may be interesting to consider, given the vast surface of the engine to be manufactured, is that of the ice rocket:2 frozen hydrogen and deuterium are used at the same time as reactor, conduit of fuel and screen against the products of the reaction.

Choice of the target: small bodies first

Paradoxically, the fact of travelling in a vessel-world makes it possible to be much less selective on the choice of the stellar target, and to get more chance to find one at short distance (on an astronomical scale). It is not indeed necessary to find a livable planet but simply a system including a star of a spectral type not very far away from the solar type (K, G or F) and abundance of small bodies. Of course, the presence of a planet offering a “practicable” surface, of Martian type for example would be very appreciable.

Among close systems, Epsilon Eridani (the system gravitating around the star designated epsilon in the constellation of Eridan) can be most interesting. It has been, by the way, the subject of research with the Green Bank radiotelescope in 1960, to seek signs of intelligent life, with negative results of course.

The system is a close neighbor of the Sun, which is its first criteria of choice. It is located at only 10.5 light-years (3.2 parsec). Ironically, Eridan is the name of the river where fell Phaeton after its disastrous race too close to the Sun. Let us wish to fall there while moving away from the Sun! The orange color star is rather close to the solar type (0.82 solar mass, spectral type K2 V).

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The infrared observation satellite IRAS detected much dust around the star, a possible indication of a planetary system in formation. It is thus very probable that the system abounds in small bodies. In august 2000, a planet of the size of Jupiter was detected at a distance of 3.2 UA (480 million km) from the star, in a strongly eccentric orbit (e=0.702) which makes it inside the ecosphere on a little more than 10% of its short orbital period (2502 days).

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If this planet has giant satellites, like Jupiter or Saturn, they could represent a semi-habitable rest place for the arkonauts.3

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Energy and travel time: the Tsiolkovski equation

The way to Epsilon Eridani will serve as a textbook case to evaluate SII strategy. We will consider a mean ejection velocity of 15,000 km/s. The fundamental Tsiolkovski equation, in its non-relativistic version (v/c<<1) gives the ratio of the departure mass to the structural mass needed to reach a velocity of v with an ejection velocity of ve :

$\frac{M_0}{M}= e^{\Large{\frac{v}{v_e}}}$

with:
M0 : total departure mass.
M : mass of the structure without fuel
M0 = M + Mc, with Mc the fuel mass
ve : fuel ejection velocity
v : final velocity at the end of the acceleration period
After the acceleration phase, there is a period of coasting flight at constant velocity, then deceleration to arrive at destination at zero velocity. This implies more fuel since we need to accelerate in the first phase a mass of fuel which will only be consumed during braking, which translates into the squaring of the exponential:

$\frac{M_0}{M}= e^{\Large{\frac{2v}{v_e}}}$

The quantity of fuel determines final velocity and so, travel duration.

We note:
Da : acceleration and braking distances (cumulated)
Dl : coasting flight distance

We define k, the ratio fuel mass/total mass:

We set:

We have Ta, the acceleration and braking durations (cumulated):

Tl, the coasting flight duration:

One wishes the acceleration and braking duration the shortest possible, so as that most of the travel is at the maximum speed. But on the other side an intense acceleration implies a strong thrust and so more massive engines and reinforced structure, to resist the thrust without deformation.

A technology being given, defining the fuel ejection velocity (ve = 15,000 km/s) it remains two free parameters to calculate the travel duration (t), the average acceleration (a) and the thrust (f) : the fuel mass Mc and the acceleration distance Da (it is supposed that acceleration and braking are totally symmetric). In the graph below, we represent the variation of the three output variables (t, a, f ) as a function of the two input (Mc and Da).

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We cannot yet carry out a reasoned choice of the input values. We know simply that we should if possible maximize Mc and minimize Da. Mc consists of fusible substance, a rare material (undoubtely deuterium for the most part). Of all the parameters which condition the feasibility of a gigaton-mass Ark, the mass of the fuel to be extracted from small bodies is undoubtedly the one which poses the most acute problems. The illustration below represents an alternative solution, a photonic sail, making it possible to reduce the structure.4 Propelled by fixed laser of very great power, for example installed on the Moon, the Ark would only take on board the braking fuel. Even with its immense surface, the sail insolation reaches more than 1000 times the solar constant in terrestrial orbit (1400 W/m²) : surface must be perfectly reflective in order not to be evaporated by the receiving power. Also, the Ark would depend on an external source which it does not control.

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For the following, we will adopt the solution of a completely autonomous acceleration with the illustrative ratio M0/M necessary to reach 1.5% of c, that is 4500 km/s. This requires a total departure mass of 46 Gt (25 for structure and 21 for fuel). For a cumulated acceleration and braking distance of 0.5 ly, one obtains an accelerated flight duration of 67 years (34 years for the acceleration and as much for braking), and a coasting flight duration of 667 years, that is a total travel duration of 734 years, to traverse 10.5 ly separating us from Epsilon Eridani.

The Ark structure, its philosophy in brief

The long strategy is based on the construction of a structure, the Ark, within which a small population, the Space Nation, could live an independent existence. This structure must allow a life at the same time completely free from Earth, organized as a whole nation and with enough diversity on all plans of interaction under which we consider the individual life.

When one wants to represent oneself physically what the Ark would look like, three preliminary constraints prove strong enough to define its general architecture.

a) Artificial gravity
The Ark must allow a normal life, according to terrestrial standards, and the first requirement relates to gravity. The acceleration of gravity results from the enormous mass of the Earth (5.97E24 kg) and it is obviously impossible to recreate it in this manner. The only alternative solution is to circularly accelerate a cylindrical surface inside which the habitants take place. The acceleration g is then:

$g = \omega^2R$

with:
g the acceleration in m.s-2
$\omega$ the angular velocity in rad.-1
R the cylinder radius in m

The acceleration g is set equal to Earth’s, that is 9.81 m/s². Ark radius, discussed below, is 5 km. So:

$\omega = \sqrt{\frac{g}{R}}$

$\omega$ = 0.044 rad.-1, that is a revolution period of 2 min 22 s.

The structure being of kilometric dimensions, the concerned mass, both for structure and fuel, will be important. Subjecting a mass to an acceleration produces a force, so as the structure needs to be reinforced so that it resists its own weight. Concerning the habitable structure, there is no choice, but concerning the fuel and the engine, one may find it very beneficial not to make them turn with the structure, so as they remain in weightlessness. The cylinder axis offers naturally a space of weightlessness: acceleration depends linearly on distance from center. For R=0, g=0. So, all the engine part should take seat in the center, or Hub of the Ark cylinder.

b) Thrust surface
However, doing a preliminary calculation of the necessary surface of the engines (as each engine is only able to provide a finite and small thrust) we find that is must be far higher than the section of a 5 km cylinder. It is thus necessary to couple to the Ark cylinder a vast thrust surface which should not rotate in order to avoid a structure overweight, while transmitting its thrust to the whole structure.

A first solution would be to place this corolla in the form of a vast ring and to connect it with cables to the cylinder hub. In this approximate version, the Ark would be drawn like princess Elisa by her eleven brothers transformed into swans in the Andersen’s tale of the “Wild Swans”.

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But if the eleven brothers had all softness for their young sister, it would emanate from the corolla a plasma blowing to ten thousands km/s as well as a flood of gamma photons, all very aggressive and extremely detrimental to any structure located under the flow.

The corolla will thus be placed behind. One should imagine the Ark as a motionless disk, the corolla, connected to a turning cylinder, the livable structure, located in front.

The architectural challenge is to transmit to the cylinder the thrust of the disk, without this coupling implying the rotation of the disk. Without also making the cylinder ‘dance’, which would occuper by gyroscopic effect if the thrust axis does not strictly merge with the revolution axis. The coupling of the two elements can only be done in one point, and this point must be located at the exact geometrical center of the Ark. Application of thrust in a single point of small surface, the central stage (diameter ~ 25 m), makes it possible to limit friction which would insidiously transmit the rotational movement of the cylinder to the corolla.

It should be added to that that the disk is not made of very rigid elements. It is essentially made of not very cohesive hydrogen ice. Such a surface cannot work in shearing. It would be the case if the corolla were to directly push on the cylinder by its center. A structure doubling the corolla, rigid enough to collect the thrust on all surface and to work directly in shearing should be extremely massive. The general rule for structures of very long range it is that a load-carrying element working in compression (as the walls of a house) is much more massive than a load-carrying element in traction (such as a cable), for an equal stress. And this more especially as the range increases. This is why it is difficult to build very high towers on Earth. Here, there are no other choices that to make the corolla work in traction, according to fasteners regularly laid out along its perimeter and its rays, by staying it to a beam which will transmit the thrust to the center of the Ark, via a bearing. This beam becomes the only element to work in compression.

At midway, we remember to reverse the thrust, so as to arrive at destination at null velocity. To turn around a structure of this size is as much less easy if its moment of inertia perpendicular to the axis of rotation is large, which is the case. It is simpler to have a second corolla, symmetrical with the first, on the front side, so as the braking jet may be correctly directed to the target when needed. The tick cushion of hydrogen ice which would form on the behind would secure the Ark from collisions with small interstellar bodies, which is very rare but devastating at a velocity of 4,500 km/s.

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c) The mass of the structure
The dry mass of the Ark as discussed here represents some 25 Gt (gigatons) or 2.5E13 kg. It would be necessary, of course, to discuss the basis of this estimation and the parameters which can intervene to reconsider it. But in any case, one has a presentiment that for a kilometric structure under tension it must be question of “gigatonnic” mass. A take-off of such structure from the Earth would be whimsical. The gravitational well is too deep and the body should be unreasonably reinforced to resist to the departure thrust. Construction will have thus to be done entirely in space. But even then, the contribution of materials neessary for its construction could not realistically come from Earth, because of energy requirements. The extraction would be done preferentially from small bodies of the solar system (asteroids and comets), whose gravity well is tiny, then conveyed in terrestrial orbit. The structure of the Ark is much larger and massive than any human artifact ever considered, and it is also that which should remain intact over the longest duration, with absolute requirements of resistance and sealing. To satisfy only one of these two requirements would require a new reflection. It is a fortiori the case when both are joined. With some exceptions, of which the structure of the first aircrafts in wood and textiles, all aereonautical structures are metalilc. There exist in the solar sytem a rather large abundance of small metallic bodies, the asteroids of type S which account for 17% of all known asteroids : even concentrating on the only light metal elements (Al, Mg, Ti…) abundance is not a problem. But to conceive a structure entirely made of metal by conventional means is hardly possible, for several reasons. Metals at native state are in the form of oxides (combined with oxygen: XnOm) and their reduction (to make them pure metals) requires high temperatures or intense amperages, which implies mass production of electrical energy. Their shaping and assembly are also energy-expensive and claim much care. They are dense bodies with a rather modest ratio of resistance in tension over specific mass. They are subjected to a phenomenon of tiredness (dislocations in the crystal lattice) which rigidify them and lead to the formation of cracks. They are oxydable in various ways, while at the same time the Ark’s interior is erosive (seasonal atmospheric cycle, humid air, oceanic layer..).

Considering by contrast that the chemical elements which mainly make the small bodies of the solar systems are lighter than metals, and that one seeks a light structure, and considering in addition that even if we are not the authors, thanks to Evolution we have in Plants an immense natural know-how in the construction of fibrous structures both resistant and self-sustained on the basis of light atoms tied to solar energy available in abundance, we come to imagine that the structure of the Ark could be built by natural growth, rather than by construction, with vegetable fiber walls. The components are as said, lighter and more abundant (CHON), they offer an excellent ratio resistance/weight and are of very safe design (they “prevent” before yielding). Especially: they are regenerated, that of which no traditional structure is able. It may seem iconoclast enough to put a ‘vegetable’ in the spatial vacuum. However, the only thing to ensure is to isolate the living cells from this vacuum, and here too biological operation can take care of it by production of a cohesive skin of dead cells in a rubber-like matrix, over some decimeters. The other advantage relates to the construction: engineering simply resumes to nourish an alive structure with simple elements taken from small bodies: H2O, CO2, nitrogen, phosphorus… The structure grows on interior orbit, by using solar energy, from an embryonic stage to kilometric adult dimensions in two or three centuries. During this lapse of time, it is habitable by its host builders. On the interstellar way, it is then necessary to provide the energy of maintenance in luminous form.

The Ark’s biosphere is made of an oceanic film, of a depth of approximately 25m, on which float ballast supporting a thin soil.

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An entire life in the Ark ?

Can one seriously consider a normal life, accomplished on all the plans, within an artificial structure far away from the Earth? Could we do it by ourselves and could we imagine without quivering a line of generations living there, which we would be the ancestor? This prospect undoubtedly constitutes the most immediate psychological brake, but not inevitably the deepest, that every normally made human being will oppose first of all to the idea of a life in the Ark.

To approach this central point, we will use of a concept that one could call the individual horizon, which parameter is a radius defined as the depth of action of the individual, on the level considered essential to an existence deserving to be lived. On all these plans, one seeks the minimum radius for which these requirements are satisfied, if it is not fully at least by combining them when it is possible.

Horizon of visual space: Dimension in which the radius is expressed: extent of the land which can be seen at a glance. It is the first signification apperception of the space, and it dimensions the whole project. On Earth, which is the radius of our visual horizon? From 1 to approximately 10 km depending on landscape. This defines the typical dimensions of the Ark. Concretely, the glance goes sufficiently far without giving the impression to feel at narrow. On the ground, a thickness of 1 to 10m of topsoil and rocks is enough.

Physical horizon of circulation: Dimension of the radius: the surface or volume which can be explored by an individual. On Earth the glance goes from 1 to 10 km, but we can move within a far bigger space, like thousands or even millions of km². From this point of view, it appears frankly impossible to reproduce what potentially offers us the whole Earth. However few individuals on Earth realize such potential in their life. A majority of people, considered in the space-time of their existence, their whole horizon of circulation does not exceed a few hundred km².
One can add to this that the radius of this horizon may be appreciably increased if there is great diversity. A thousand km² of desert do not offer the same radius of action, on that level, than a hundred km² in which one would find a city, a forest, fields, a river and any other elements of landscape diversity. One would want to maximize from this point of view the diversity offered by the natural environments of the Ark by reproducing the main part of the great terrestrial ecosystems.

Moreover, an artificial structure as the Ark offers by its design several levels, going from the center towards the periphery, while terrestrial surface is presented as purement bi-dimensional, without thickness to be explored with the exception of sea-beds or cavities. These various levels offer a completely new diversity unknown on Earth: micro-gravity spaces, spacewalk on the central beam or in galleries within the fuel hydrogen ice, oceanic background and other surfaces and volumes which will be detailed when discussing the structure. All places in the Ark, in surface as in volume, can be designed to be accessible at walk. Some will be very diversified, others rather monotonous. Together, they offer a very large radius of circulation. The maximum visual horizon being about 10 Km, one can start to consider on the same basis the habitation area. It would be a cylindric surface of length L=10 Km on a diameter of 10 Km (or a radius of 5 Km). The habitable surface A0 is:

A0 = 2πRL

That is A0 = 314 km², representing the primary radius of the circulation horizon, something like ‘dry land’, offering conditions of existence in all points comparable to terrestrial standards. It is difficult to rigorously quantify what the spaces developed on the basis of this primary radius represent, since surfaces and volumes are concerned at the same time. Without claiming to give anything other than an estimation, one can however ensure that this radius will be multiplied by ten. In magnitude, an Ark whose visual space horizon is set to 10 km should offer a space of circulation comparable to a space on Earth that a horse can traverse during one day.

Of course, even if one does not feel at narrow in such radius of circulation, it could look very thin when one imagines – and how not to do it - about the terrestrial immensities. But two plans are then confused. Terrestrial space, let us repeat it, is only potentially available to us. Only a negligible minority of people happen to travel from one pole to another or through all timezones. And even the great travelers never explore more than what is within reach of their steps. When we go to China, which we explore best is the seat of the airplane taking us there. And it would be specious to affirm to have been “crossing Japan” because one flew over it at 10,000 meters of altitude. And when one visited China, the actual radius of circulation was by no means comparable to the size of this nation. It was summarized to some visited places, some natural curiosities, a city or two, and within these cities a few remarkable places, with our hotel room probably the best explored place of all the tour, said without any irony. The real circulation space is not indexed to terrestrial vastness but to time. That is the actual criterion. The fact of potentially having an immense world is not at all negligible. But that is a moral aspect which should be considered separately. It may seem important that a vast world is available where to carry our steps, but if one adds up over our whole lifetime the spaces where one will have been able indeed to note our presence, it is probable that they will not exceed the radius of circulation under consideration for the Ark.

Horizon of social interaction: Radius dimension: number and diversity of the arkonauts population. The term arkonaut designates the inhabitants of the Ark. To reach the minimal threshold of diversity, it is needed in other words that one can during his whole life meet people who he never met before. It is also what one could call the threshold of anonymity: while walking in the crowd, one meet unknown people in proportion as large as known people. That corresponds to what happens in a small city, that is a population ranging between 10,000 and 100,000 inhabitants, with an average set for the convenience of this article to 50,000 inhabitants.

Comparing to Earth, Ark should carry a maximized human diversity. However, it is undoubtedly necessary to imagine that the settlement is done primarily by natural growth. The initial settlement, carrying out the way Ground-Ark could include as few as 2,000 families or 5,000 people, adults and their offsprings, knowledgeable in fields useful to construction and maintenance of the structure and the engines. And for the successor, a “meritocratic” ascent formed of volunteers selected for their social utility within the framework of the project. The time of acclimatization and demographic balancing, including the possibility of a return to Earth, will undoubtedly be higher than a century.

Horizon of social activities: Radius dimension: diversity and intensity of the activities constituting the reason to act at the collective level of individuals. An Ark carrying a branch of humanity towards a nearby stellar system, on secular durations, would structure around two primary functions: ensure propulsion of the engine, and maintain the life.

Propulsion: it consists of two symmetrical phases, acceleration and braking. Between the two, the Ark is in coasting flight at maximum speed. As one wishes to carry out the maximum of the way at this maximum speed, in ordern to shorten it, one will seek to reduce as much as possible the duration of the phases of acceleration and braking, and the coasting flight will have to represent the major part of it. Also the strictly propelling function should only concern a short segment of a few decades before departure and preceding arrival. However, the competences concerned with the propelling function preserve an essential preroagative during coasting flight: provide the energy needed to maintain the life in the Ark, that is for the main part the solar energy (when the term does not carry confusion, we will use it to indicate luminous energy) diffused within the structure and allowing life of the ecosystems, as well as the maintenance of the “thermodynamic machine” regulating Ark climate. The energy used by the anthropic activities (industry, transportation, domestic activity) is included, representing a negligible sub-total. Physically, this function is achieved in the center of the Ark, in what one will indicate as the Hub, in a microgravity area, as well as in the Beam and within the corolla, in weightlessness (or almost, since the mass of the structure will create a natural gravity of a millionth gram). One will include in the activity of the Hub all the industrial activities which it may be interesting to perform in low weight.

Life: it is at the same time about the interior ecosystem of the Ark (content) and its walls (container). The Ark is a closed system with a short cycle if compared to those known on Earth. Given the immediate cause/effect relationship between the global functioning of the Ark and the existence of its inhabitants, one can predict that those will develop particularly sharpened skills. The Ark being globally, and totally, an alive being, it represents a source of constant interactions for its inhabitants, either if it question of taking care of it or to be looked after from it. The nature of the “propulsion-life” bond represents something philosophically stimulating, because of the “mise en abyme” of the action which it founds. The Ark shelters man, and man injects energy making it possible to the Ark to live. That resembles the endosymbiose joining together the eucaryotes cells and the mitochondries. It is about a relationship of total mutual dependance, in a conscient form at one part (asymmetry founding a total responsibility) and which seals a unity of destiny all the more intensely felt than an alive being is totally master and totally slave of an another. Interesting dialectical. On the level of individual moral construction founding political systems, the small number of the population is an asset to develop an “Athenian” democracy without political representative body, which increases the richness of social interaction of individuals, insofar as a direct and not mediated power is exerted.

Genesic horizon: Radius dimension: capacity to generate. A very delicate question would be that of demographical control. The Ark being a closed world largely optimized, there is no question of leaving the simple natural growth to control demography. One does not need either to set excessive constraints, population being able without any doubt to grow of up to a factor of 3 without consequent damage. However, the question would be obligatorily set for a so long duration that the balance between personal freedom and collective interest should be solved theoretically. Within a democratic framework one can imagine the following social pact. The first child would constitute an indisputable right, that each woman would concretize when she would like it, with the simple duty of declaring it to allow for demographical planning. The extension of the family to two children would then be decided at random depending on the balance requirements formulated by demographic projections. Concretely, each woman would declare each year their “child project” for that year, in yes/no form, and for the whole of their fertile period (I would desire N children in all). That would be a simple declaration, revisable without notice and nonconstraining. One would draw a demographic projection from it, from which an opinion would result, in the form of a random choice. Each troop of women (a troop is defined by individuals of the same age) would be entitled to the random choice. The randomized names would depend on the wish expressed for the year (if a woman desires a child on that year, his name would be in the list to be randomized) and each name would be weighted in proportion of their parental project already carried out (a woman wishing 3 childrens and not having any would have more rights than a woman wishing 4 childrens and already having 3). The remaining question, subjected to the political appreciation of the arkonauts, would be to determine the applicable constraint (if any) when a woman falls pregnant when the random choice had not granted child to her. If the wishes not carried out by other woman in the troop balances it then all is well. The question takes a more delicate turn if the total indiscipline of a troop would burden the procreative right of the youngers. At worst one can imagine a penal sanction, but it is foreseeable that, like all social constraints originating with a very comprehensibile need, education would suffice so that things occur orderly or almost.

Spiritual horizon: Radius dimension: intensity and diversity of spiritual life, intended as the whole of the activities mobilizing cognition. A way of measuring the radius of this horizon could be to evaluate the depth and the richness of the materials available to mind to think about reality and itself.

Compared to what the Past can deliver, the Ark would embark the whole of terrestrial memories which should represent some 1E20 bytes in magnitude, that is the whole of what is currently registered on paper, magnetic or optical media, with or without repetition, everywhere and in all languages. The Ark will also have access to a “differed present” thanks to the radioelectric link with the Earth, all the more differed since the Ark is moving away. A laser link could be imagined, so as to minimize dispersion, in the infrared band which would get less noise from the plasma emissions. For a laser power of 1 MW at lambda = 1 micron, the bandwidth would be of magnitude of 10 MB/s at 1 ly and 100 KB/s at 10 ly, similar to an average internet link.

Compared to the Present, the spiritual horizon is identified to the horizon of social activity previously discussed. Arkonauts live a morally new situation, in lived and in long-term aims. They should develop an original mentality. The need of getting along would come first. The word trajectory reminds of “transient”. But such transient is a whole life and a whole civilization, with the result that the stellar goal will become almost secondary. The majority of individuals populating this travel will belong to a generation “not leaving, not arriving”. For this majority, the end of the way would just appear like a distant future. Certainly, in background the reach of targets will structure the community, but the stake making the happiness of the travellers will remain for the humankind its present.

Compared to the Future, the colonial objective will require a thorough reflection of what will have to be done once arrived at destination.

Either the target planets present conditions of existence allowing a settlement “naked head”, either they require terraformation. With the first case is associated a weak probability, as previously said. It is thus rather necessary to imagine a life of orbital two-ways travels between an Ark forming a comfortable base camp and life on surface in protected conditions. A terraformation represents a long-term task, exceeding individual lifespan, and arkonauts would live again what lived their ancestors who built the Ark, with this only difference that for the ancestors the base was a planet and their future horizon the Ark, while for the newcomers the base will be the Ark and their future horizon, the planet which becomes gradually livable.

To the multi-century duration of the task, there is a real ethical problem, which arises in all cases where the target planet is not deprived of life: what to do with indigenous life ?Of course, one does not imagine to colonize a planet populated by beings morally equivalent to the human being. But if the planet is ready to receive a form of life based on the chemistry of carbon, then it is possible, to differing degrees, that this one already developed at its surface or in sub-surface an original form of life without continuity with the forms of terrestrial lives which contain the Ark. The idea to sterilize a biosphere appears at the very least monstrous. On this assumption, it is necessary to imagine the existence within a mixed ecosystem.

As a conclusion

The travel duration, more than seven centuries on the adopted hypothesis, constitutes the most striking characteristic of an interstellar travel led by classical means. The most immediate objection which comes to the mind is that it would be perhaps wiser to wait that Physics makes sufficient progress to authorize interstellar travel in “decent” durations. And partly, history of physics seems to encourage us there. Few fields of knowledge indeed progressed at a faster rate than physics over the last four centuries. But on another side, in fact precisely the already achieved progress, crystallized in a solid building, shows well and to the point that crossing of immense spaces is expensive, either in time or energy. Perhaps is physics mature enough so that we should take it seriously as of today? To abolish time while spending immense quantities of energy does not cost anything to imagination, but nevertheless, energy keeps a rare good. Would not be time to drop sterile dreams to embrace fertile dreams? It is on this bet that this reflection was carried out. Energy is for humanity an exogenic good which must be extracted to the Universe, it is a conquest. As the fable says, “One fights for everything he swallows”. Humanity however has its time. It renews itself with its generations. It does not require, to last without effort, of nothing else than a reconstituted environment and a modest amount of energy to maintain it. And yet, even in the long strategy, one need an insane amount of energy. 99% of fuel disperse in the Great Outside and propels the Ark, 1% only feeds the sun shining on such a world.

At the scale of the beginning of XXI century, the Ark is a project at the border of fantasy. Everything appears disproportionate, whether it is the amount of fuel or the dimensions of the structure. But to set the real height which is necessary to cross, to set masses, lengths and energies, to determine the level of technological advance of the travellers, draw the broad outline of a society to come, all of this, even if future would not retain nothing of it, may help the birth of a future.

1. For more details check http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html []
2. J. Post, “Hydrogen ice spacecraft“, AIAA, Space Programs and Technologies Conference, Huntsville, AL; (1990) []
3. A simulation of the system can be seen here: http://media4.obspm.fr/exoplanetes/base/systeme.php?etoile=Epsilon+Eridani []
4. G. A. Landis, “Small Laser-propelled Interstellar Probe“, Presented at the 46th International Astronautical Congress, Oslo, Norway (1995) []

### 135 Comments to “Interstellar Ark”

View Comments in: Français (175) Italiano (6)

1. 1
xantox

One approach to widen the horizon of circulation could be to rely on immersive virtual reality, which should be within the technological range of this project, so as to take aboard a detailed reproduction of Earth’s surface, including cities and landscapes, and to be used as well as a ground of exploration of toy worlds in order to prepare future colonization. That suggests that the computational power of arkonauts could be as important as their propulsion power, in such a travel toward new worlds.

2. 2
Alan Crowe

Option four: Genetically engineer a much longer human health span.

Once the human life-span is up to 70million years, spending a few thousand years to travel to a new planet will not seem like a large investment of time

3. 3
Carl Witthoft

I’m on the side of various SciFi stories which show such an Ark’s population rapidly losing any memory or concept of Earth. The residents soon form their own religion(s), view the Ark as the one and only locale on which humans reside, and so on. In fact, after a few centuries, it’s more likely that, should a habitable planet be found, the religiious proscriptions against leaving the Ark would stop them from so much as attempting an exploratory landing on a orbit-bound environment (as opposed to the free-flying Ark).

4. 4
H-E

Wow! What a great article, really.

However, there is two points I would be very interested to get your opinion about :
1- Hibernation.
You mention possibility of a “hibernating crew” in SP1, but didn’t get too deep about it. Hibernation is often considered as the most “possible” way to make mankind to travel in outer space and seems pretty much in reach of our current technology, when compared to the ark. What do you think about it? I don’t know the scientific point of view on the subjet but I’m very curious about it, as it seems _almost_ realistic.

2- Collision.
What’s about collision with smaller object while travelling? Correct me if I am wrong, but colliding the ark with literrally _anything_ (big dust, rock) at this speed, would happen to be devastating. Even assuming the hull is not breached, dust collision would probably cause the ark to “erode” (some kind of). The hydrogen ice part does not seem very safe,as it does nothing but to reduce the probability of a dangerous collision on “a vital point”, since the ice “shield” most of it.
Is the probability of collision while travelling during century is that low or shouldn’t the ark be equiped with some kind of “deflector” (or any kind of “protective shield”)?

5. 5
Matt Hickman

Given the
1. technology of programed self-replicating machinery (down to nan-scale),
2. the ability for those machines to harvest raw materials from a target solar system,
3. a technology that will allow the machinery to use genetic information, human developmental information and artificial wombs to allow for the birth of a generation of humans de novo at the target system once preparations have been made,
Many of the constraints of the above disappear.

6. 6
Ben

We already have an “ark”. We just have to provide a sun-replacement in orbit, and take the entire system (planet, solar replacement) with us.

Great article.

7. 7
Travis Rivers

Humanity in 140 generations produced multiple “religions,” despots, plagues, and self-destructive tendancies, enough to frighten even the hoplessly optimistic, but evidently not all. The unravleing of the social fabric abord the ark is an intrigueing subject of speculation, say sometime during the 90th generation as all chaos reigns a smalll group discover early records from the departure at homeworld…

I love the article.

8. 8
IMarvinTPA

Can’t we just send all our Accountants, Middle Managers, Account Executives, and Telephone Sanitizers? We can call it the “B” Arc.

IMarv

9. 9
Gilgamesh

2. Alan Crowe wrote:

Option four: Genetically engineer a much longer human health span. Once the human life-span is up to 70million years, spending a few thousand years to travel to a new planet will not seem like a large investment of time

Alan, the problem is exactly the same if one takes as a basis a lifespan of 70 M years (wow!). Arkonauts are human beings, they seek the same happiness, the same quality of life as those who live on Earth, I think it is realistic to say that. Nobody plans to live, generate and die in a jam jar. One thus needs a structure able to ensure such quality of life.

10. 10
hyc

The fuel/energy requirements for deceleration are not necessarily as high as you calculated - you should be able to use the gravity of the destination star system for a large part of that.

11. 11
IMarvinTPA

This comment is up for debate, but I want to offer a different source of power.
Stellar, Interstellar, Galactic, and Intergalactic space is composed of plasma. Generally referred by astronomers as super-heated gas or ionized gas. All three of these are the same thing and are very electrically excited.
There are currents of electricity connecting stars together called Birkland Currents. The target star should be one that is electrically connected to our Sun and the ark could tap into it to provide power. Life on Earth would also do well if we could tap into the interstellar power grid.

IMarv

12. 12
Green Emissions

It seems to me that an interstellar ark would work well if one of its major agricultural products is cannabis magnifica. The time would seem to flow so much faster for everyone if a fine mist of the stuff were flowing everywhere.

13. 13
IVORY LAB » Travel light

[…] How do you get from one star system to another?  Build an ark complete with mountains, oceans, and cities.  An article entitled Interstellar Ark provides the details on how we can achieve this feat.  This is a far out idea. I like it. My only criticism is the underlying notion that we need to find other habitable planets to colonize.  What are we, barnacles?  Do we have to keep on jumping from one rock to another?  Let’s just build the ark and go for a joy ride around the universe.  There’s no need to stop and get stuck on another planet.  Still, the article is a fascinating read, even with all the math thrown in. Trackback · […]

14. 14
Gilgamesh

3. Carl Witthoft wrote:

I’m on the side of various SciFi stories which show such an Ark’s population rapidly losing any memory or concept of Earth. The residents soon form their own religion(s), view the Ark as the one and only locale on which humans reside, and so on. In fact, after a few centuries, it’s more likely that, should a habitable planet be found, the religiious proscriptions against leaving the Ark would stop them from so much as attempting an exploratory landing on a orbit-bound environment (as opposed to the free-flying Ark).

Carl, the travel is “just” seven centuries. Yes, that is a long time. But that remains largely in the magnitude of historical durations for which we keep a very sharp memory of civilization, great men or events. We are able to reconstitute the daily activities of people in the Rome of 1st century BC, 2100 years before present, and we know what we owe to this civilization. We remember well Alexander the Great, who lived 2300 years ago.

Moreover, the “radio” link with Earth is preserved. Calculation is mentioned in the article. Using an IR laser link, with an emission power of 1 MW, one gets a bandwidth to Earth of 10 MB/s within 1 light-year and 100 KB/s within 10 light-years, similar to a normal internet connection.

On the other hand, I agree with you that the moral and spiritual trajectory of these people could be new. One may consider that a kind of civic worship of the Arch would develop, Arch considered as a living being depending on travellers as travellers are depending on the Arch.

The linguistic problem is also interesting to consider. I imagine a bilinguism with an “arkean” language, for public expression, undoubtedly an anglophone Creole, and “archaic” terrestrial languages which would keep a right.

For settlement of the distant world, I consider difficult that at 10 ly from the Earth (it is really the outskirts of the solar system) one can find a livable planet just like the Earth. It would be an incredible stroke of luck. The Arch would thus remain “the” place of reference, no matter the religious interdict. The host planet would become populated only very gradually, without urge. In fact, finding a distant planet is not really the first goal, what is essential is to find energy near another star.

15. 15
Gilgamesh

4. H-E wrote:

Wow! What a great article, really.
However, there is two points I would be very interested to get your opinion about :
1- Hibernation.
You mention possibility of a “hibernating crew” in SP1, but didn’t get too deep about it. Hibernation is often considered as the most “possible” way to make mankind to travel in outer space and seems pretty much in reach of our current technology, when compared to the ark. What do you think about it? I don’t know the scientific point of view on the subjet but I’m very curious about it, as it seems _almost_ realistic.
2- Collision.
What’s about collision with smaller object while travelling? Correct me if I am wrong, but colliding the ark with literrally _anything_ (big dust, rock) at this speed, would happen to be devastating. Even assuming the hull is not breached, dust collision would probably cause the ark to “erode” (some kind of). The hydrogen ice part does not seem very safe,as it does nothing but to reduce the probability of a dangerous collision on “a vital point”, since the ice “shield” most of it.
Is the probability of collision while travelling during century is that low or shouldn’t the ark be equiped with some kind of “deflector” (or any kind of “protective shield”)?

Thank you HE

Hibernation is indeed often mentioned as a possible solution, but I think that it is a mistake. True, the vessel being less massive one could go quicker, say to c/10 with a small vessel. But even at this speed, the travel would still take one century. The calculation mentioned at the beginning of the article gives what would be possible by taking full advantage of relativistic proper time slowdown. But that means that one must master massive fuel ejection at speeds much higher than c/10 (which would be the coasting flight speed). One can accelerate particles at ultra-relativistic speed in large accelerators, but at the price of enormous amounts of electric power. Here, it is the fuel itself which should provide the energy for its own ejection, or it will not work. And it is not possible with thermonuclear fusion to exceed temperatures of 10 MeV, so one is still far from relativistic speeds.

Thus we have a travel which remains of about one century, for the nearest target. The crucial question which arises then is: does hibernation makes it possible to lengthen human life at the point of largely exceeding one century?

Because obviously, it would be useless to make asleep thousands of people if they would awake as old men on arrival! It is necessary to awake people in full possession of their faculties, say less than 60 years on average. The phenomenon of hibernation such as we know it, does not make it possible to lengthen the life of the mammals practicing it, it is just to spend winter and avoid food shortage.

Hibernation would just avoid finding the wait too long and suffering from the exiguity of a small vessel. But, if there are “sleepers”, inevitably there would be also “watchers”. I do not imagine for a second a vessel of “Sleeping Beauties” where only computers take care of everything. I think that whoever knows computers a little knows why this is not realistic

It is thus necessary to imagine that groups of people would in turn awake, make decisions and bring up children. For that one needs a minimum of comfort, therefore of space and natural environment.

Finally there is the arrival. The planet most probably does not present all terrestrial standards. Perhaps with some luck one will find something like Mars : it would be already fantastic. Thus one would need at first to make closed buildings as comfortable as on Earth. To build them, one need many people, and lot of time, surely more than one generation. And a comfortable environment is still needed in the wait, which by hypothesis cannot be the vessel himself.

By any viewpoint one considers the problem, a “quick” travel duration implies some kind of bottleneck.

Now about the risk of collision. Interstellar space is empty, but really empty, at a point which one can difficult imagine. And that is already the case for the interplanetary space. On the other hand it is true that consequences of a collision with meter-sized bodies are indeed devastating at 4500 km/s. Calculation made, it appears that it is already problematic for centimeter-sized bodies. There are several lines of defense :

1. A radar on the front, and possibility of maneuvering the Arch. One needs approximately 1 hour to move the arch away from its trajectory of a distance equal to its diameter. The corolla is indeed directional within ±10°. One can imagine that the maneuvering would be precisely defined, in order to be able to go “full power” in very little time.

2. Mirrors with temporal reversal. By amplifying the received echo towards the target, one could concentrate a great amount of energy so as to vaporize it.

3. Electromagnetic shoot. The central beam on the front (> 10 km) can shelter an electromagnetic accelerator making it possible to send projectiles on the target

4. Alarm probes. On the front of the Arch, several probes could fly with an advance of several months to check for bodies.

5. The fuel shield would secure the Arch against any impacts of bodies smaller than a centimeter.

6. In the worst case, a collision would make a hole in the Arch, from side to side. If this happens, it would be possible to empty the ballast of perpendicular continents so that they fall in the hole, stopping it while waiting to repair it.

16. 16
Todd

I like the article, it’s very futurist and represents the kind of endeavor that leaves a positive mark on history, however I am constantly abhored by negative statements about what can or cannot be accomplished.

Specifically, the comment “the famous constant of Einstein c, the speed of light (3E8 m/s), represents an horizon speed which is impossible to exceed and which is even extraordinarily difficult to approach,” which strikes me as shortsighted and similar to the things people used to say about flight, or going to the moon, or the sound barrier, or for that matter, hundreds if not thousands of scientific and technical achievements.

I prefer to maintain an open mind, something I think scientists should always do.

17. 17
Gilgamesh

10. hyc wrote:

The fuel/energy requirements for deceleration are not necessarily as high as you calculated - you should be able to use the gravity of the destination star system for a large part of that.

Hmm, no, I do not see how the gravity of the distant system could be made profitable. The target star would accelerate the Ark towards it, not slow it down. For Epsilon Eridani, the escape velocity at 1 astronomical unit from the star is approximately 38 km/s. It is then needed to add this velocity to the 4500 km/s coasting flight velocity, that is a supplement of 0.9% (in fact less, because approximately 30 km/s out of the 38 will be used to put the Arch into orbit around the target star).

18. 18
Gilgamesh

6. Ben wrote:

We already have an “ark”. We just have to provide a sun-replacement in orbit, and take the entire system (planet, solar replacement) with us. Great article.

Thank you Ben.

Yes, we have a natural ark, and the interstellar ark is not there to replace it. In all, just 5 000 or 10 000 people would leave the Earth to live in the Ark (and then would grow naturally). That is completely negligible compared to the 6 billion people that we are on Earth.

19. 19
Gilgamesh

16. Todd wrote:

I like the article, it’s very futurist and represents the kind of endeavor that leaves a positive mark on history, however I am constantly abhored by negative statements about what can or cannot be accomplished.

Specifically, the comment “the famous constant of Einstein c, the speed of light (3E8 m/s), represents an horizon speed which is impossible to exceed and which is even extraordinarily difficult to approach,” which strikes me as shortsighted and similar to the things people used to say about flight, or going to the moon, or the sound barrier, or for that matter, hundreds if not thousands of scientific and technical achievements.

I prefer to maintain an open mind, something I think scientists should always do. .

Todd, I ensure you that I am one of those who are deeply troubled by pessimistic considerations about man’s nature (like, we are too stupid, too evil, etc). I am deeply optimistic. But one thing is sure : we do not decide how Nature is. If c is a limiting velocity, it could be that it is like that, and that’s all. This has nothing to do with our moral or intellectural nature. It is not a punishment. Nobody wants to harm us with that. But the deepest physical theories shows that it is a limiting velocity. It is not at all like the sound barrier for example, it is much more fundamental. The question is: what do we do then? The refuse to recognize it? We acccept it and we resign to do nothing? Or we accept it and we put ourselves in the position to go nevertheless?

20. 20
Hugues

In 700 years it is not unlikely that the human species will have either transcended itself into machines or wiped itself out.

We are probably unable to build anything complicated (outside of a few large stone buildings) that can last a few centuries.

This ark is a nice fantasy. We are stuck on this planetary system for a long while, unless some spectacular new physics comes along.

21. 21
That’s Far Out » Interstellar Ark :: Strange Paths

[…] Interstellar Ark :: Strange Paths The concept of star travel, from planetary system to planetary system, is at the same time completely familiar and completely uncharted. Familiar, as we have certainly all heard of science fiction stories set on a far galaxy, where planets are nations or provinces of an empire. The characters usually move from one planet to another during intervals of time consistent with the story. The actual travel appears just like a formality, which the future advancements of a Triumphant Physics will put within reach. […]

22. 22
krisvek

Great article. Certainly, it paints a less-than-expected (by most, at least) view of how we might explore the stars and colonize other worlds. Reminds me of the novel Forever War a bit.

I personally have come to the conclusion that for the time being, we should abandon such ideas of interstellar travel and focus on what we have in the neighborhood: our own solar system. Beyond it, there is a vast void, so why leave? (other than for the sake of exploration, achievement, etc.)
Particularly, if we are at all thinking that we can develop and build an Ark of any sorts, then we can certainly instead build an orbital city (around Earth, or any other planet in our system). Of course, the city would not necessarily need to be ‘orbital’, it could always blast off on a trajectory and land in orbit around another planet if there was the desire. I think that there is plenty of development to be done within our own system, and plenty of resources available too. Just imagine how much mineral and gas are available for our use within Jupiter and it’s satellites alone? Or the asteroid belt? And of course, we could have our hand at terrestrial settlements also, whether it be Mars, the Moon, or Titan or something. After we have exhausted all of our resources in our own solar system, I imagine enough time will have gone by to allow us to either reach these interstellar targets more easily, or to have resigned to dealing with the more difficult options we have available and being better prepared to undertake the endeavor. After all, we have a pretty generous time limit until our solar system expires, so no reason to rush (again, other than for the sake of exploration and achievement).

23. 23
Gilgamesh

20. Hugues wrote:

In 700 years it is not unlikely that the human species will have either transcended itself into machines or wiped itself out.

We are probably unable to build anything complicated (outside of a few large stone buildings) that can last a few centuries.

This ark is a nice fantasy. We are stuck on this planetary system for a long while, unless some spectacular new physics comes along.

Hugues, the whole idea of the Ark is precisely that one should not wait *so much more* from the human capacities. A little more, okay. But while remaining realistic. It is the starting point: “Nothing new under the sun”. Let us see what we could build, starting from our *current* potential, simply intensified by political union (and still, of circumstance).

The idea is to seek a “lever” in Physics which would enable us to make large things with little means. In the traditional idea, the “simplest” is to wait a new Einstein proposing a mean to go there like by taking an airplane. I think that it is a phantasm, an illusion.

Then if not: we have small frozen bodies in the solar system, and much luminous energy. We are around a star, let make something useful of this! We have at hand the genius of vegetals, and it does very well in building solid fibers, provided that there is some water, carbon and light. What man brings, it is its genius to lay out all these elements in the right order, to create a new astronomical body, hollow and accomodating, and which would have this originality to be alive.

And why not?

24. 24
Mal-2

Green Emissions wrote:
18 February 2007, 6:38 pm

It seems to me that an interstellar ark would work well if one of its major agricultural products is cannabis magnifica. The time would seem to flow so much faster for everyone if a fine mist of the stuff were flowing everywhere.

Except that it wouldn’t be long before they were going 15 miles an hour in the slow lane, exclaiming how fast they’re going.

Then they’d just turn off at the nearest Milliway’s, because they’d already eaten everything in the Ark.

Mal-2

25. 25
Johan

i have an idea..cant we hichhike on a comet a long way, without spending to much fuel. Or maybe we can accelerate a comet in our solar system, then adjust the bearing, and then ride/live on it

26. 26
Rob Knegjens

Physics is the oldest and most modern of the sciences. If we are willing to imagine further spectacular break throughs (that would aid us greatly in space travel) in such a matured science, surely it is also conceivable to imagine a lot of key advances in the younger sciences, like human biology. Hibernation, as you described it, might age the body, but what about (something resembling) cryogenic freezing? I doubt anyone would put serious money on biologists making no advances in such a field in the next 20 years.

2. Gilgamesh wrote:
I do not imagine for a second a vessel of “Sleeping Beauties” where only computers take care of everything. I think that whoever knows computers a little knows why this is not realistic

You seem to put little faith in computers. As I’m sure you’re aware, there has been a countless number of successful unmanned space missions. What exactly would human “watchers” be used for on a space flight with cryogenic cargo? A simple safeguard to protecting the life of the inanimate crew would be to simply thaw them the moment communication with earth is lost. They could then re-establish communication (assuming the hopeless computer wasn’t capable of doing so itself) and go back to sleep trusting earth will continue steering the craft.

Finally, considering the significant cost reduction in sending cryogenic cargo, we could improve our chances of success by sending a large of number of such crafts. Statistically we will have an awesome chance of at least one making it

27. 27
Tim

Great article, just wanted to provide a link to a short story by Asimov that I thought was relevant. It’s called the last question and it deals with humanity’s future expansion into the universe.

28. 28
ShakaZ

Great effort of thought & a lot of interesting replies…
The question is; where do we sign-up for the interstellar travel?

Let’s assume this project generates sufficient interest from us earthlings to start building the ark by the beginning of next year, how much time would we need till the big launch?

29. 29
Ache

28. ShakaZ wrote:
The question is; where do we sign-up for the interstellar travel?

I was wondering the same. Assume that one think this project is grandiose, what can this one do? For exemple, are work and research in cognitive sciences of any support toward the Interstellar Ark. I think they are and there are links, for instance with immersive virtual reality, as said xantox in the first comment, that is, wide stimulation range for education and delight.

30. 30
Gilgamesh

25. Johan wrote:

i have an idea..cant we hichhike on a comet a long way, without spending to much fuel. Or maybe we can accelerate a comet in our solar system, then adjust the bearing, and then ride/live on it

I thought about it (I am not the only)… Generally, the small bodies of the solar system (gray bodies, the small ones and those “without ranks” )… shall intervene in many dreams of humanity, because they are “within our range”.

But to divert a comet just “as it is” it is not possible:

1. One wants to live on it, or inside it. Above: gravity on the surface of a comet is too weak. For a spherical body of 50 km in radius (that is a large comet), of density 2 (formed by a substantial quantity of rocks), surface gravity would be of 0.028 m/s ², that is 1/350 times gravity on Earth. That is, practically zero. Inside: to generate appreciable gravity, it would be needed to dig into the body, make a cavity and make it turn. The problem here is that these bodies have a very low cohesion. They are heaps of gravel with some ice. If you put them into rotation, they burst.

2. The body should be accelerated. Now a comet is *very* massive. One can imagine to take a smaller one, but a comet of 50 km radius and d=2, represents about 42 000 Arks (only taking the structure, without the fuel)… That is 1e18 kg vs 2.5e13 kg. One wants to accelerate all that. Of course one could imagine to consume part of the mass in propulsion. But energy must be extracted from the small body, then. If one manages to breed the deuterium which it contains one can transform all hydrogen in fusible material. But water, H2O, it is 16 parts of non fusible oxygen, against 2 parts of fusible hydrogen. Without counting all other more massive atoms, also not fusible like O. In short: to accelerate a rough body, it is like wanting to build a car with rough ores while also extracting the oil from it (this last image being a bit exaggerated).

31. 31
Sam Denton

Interesting article, with a few novel ideas. Obviously, the Ark is “just” a space colony, albeit a more self-sufficient model than most. Back in the ’70s, NASA sponsered a lot of research into many of the issues that you have discussed. The most interesting is the need to prevent “solipsism syndrome”, a feeling that the world is an artificial creation that leads to extreme depression. (This is obviously more difficult when the world actually is an artificial creation.) One of the suggestions is that most of the habitat not be visible from any one spot; that there is an impression (true or not) that there is the potential for something new to see just around the corner.
Also, I recall (but don’t have at hand) some USENET posts by fans of the TV show “Babylon 5″ in which was discussed the engineering of bearings between large spinning and non-spinning habitats. Based on my fuzzy recollections, I don’t think that things are as difficult as you suspect. Instead of a design resembling a soda can between two dinner plates, one could have several “cans” arranged in a circle. The bearings would easily last for millenia and could easily be swapped out if or when repairs were needed.
Anyway, thanks for a provocative article.

32. 32
Gilgamesh

26. Rob Knegjens wrote:

[..] [1] hibernation, as you described it, might age the body, but what about (something resembling) cryogenic freezing? [..] [2] [..] A simple safeguard to protecting the life of the inanimate crew would be to simply thaw them the moment communication with earth is lost. [..]

1. Cryogenic freezing is impossible. The cell is an aqueous body which has its own thermal conductivity. You can put the surface of the body (including the internal cavities: respiratory system, digestive…) in contact with a very conducting body at absolute zero (aluminium, a special liquid, or something), but the cold will take some time to propagate inside the body. If that does not go quickly enough, the body dies by hypothermia. If that goes quickly enough, but at the rate constrained by tissues thermal conductivity, the cells will develop crystals of ice tearing the plasmic walls, because water conductivity is too low to make it freeze without forming crystals. And the problem would be the same to heat back this body, though at least there one can conceive to diffuse heat uniformly (something like a very sophisticated microwave oven). But the problem of congelation keeps there.

These are unpleasant considerations, but they are essential if one claims at least a bit of realism. One cannot freeze a body without damage, not that of a mammal in any case. Hibernation it is slowing down metabolism, not congelation. It is not at all the same thing.

2. if we were able to hibernate at the point to multiply by ten the human lifespan I would say that yes, on paper. Moreover, a cargo of frozen bodies is easy to control, one has just to maintain the right temperature, but hibernation (not freezing) requires to control each body very finely, and to feed it consequently. A body in hibernation is alive and a living body has its requirements. The terrestrial link (which is not realtime, it has several years of lag) cannot constitute a solution to react to unforeseen at the appropriate time. And I don’t believe one can be able to foresee *everything*.

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Michael D. Bryan

Great article. Thoroughly researched and even better reasoned.

It puts me in mind of something Eisenhower said: In preparing for battle (or intersellar travel) I have always found that plans are useless, but planning is indispensable.

The collision between the known and the unknowables of the future is always problematic. The natural conclusion to be drawn from this excellent planning is simply that we aren’t nearly ready yet.

It is questionable whether we even possess the ethical sense to understand whether it is permissible for a species to expand beyond the solar system of it’s birth, let alone possess the acumen and organization required to actually move a viable human population (along with all the ecology of support we would require) to a new solar system. Too frequently, we forget that man thrives only within the mesh of Earth’s environment; severing us from Earth for any length of time results in death. We are far from understanding how to accomplish birthing a spore containing all that is needed for the survival of an independent branch of our species. In fact, it is entirely possible that no species, even an extremely clever one, can survive permanent separation from the ecology of it’s birth.

What this article makes abundantly clear is that we will likely explore beyond our solar system only by proxy of our machines. It is clearly much more efficient and doesn’t require the grand scale social and ecological engineering that moving populations does. I would be really interested to see an analysis of the same scale and scope of how we could accomplish such extra-solar exploration by proxy. The author touched upon this, but did not explore the practicalities fully as well as some of the grander themes dealt with in speculative fiction.

For instance, will we make our exploring machines the first wave of a interstellar project of interstellar imperial conquest as in Brin, Bear, and Benford’s second Foundation trilogy? Will our machines go forth and prepare the way for our eventual colonization by committing genocide of native ecologies in our names, turning irreplaceable diversity into mulch for our terraforming projects? Or will they go with strong prohibitions on destruction of xenotypes (a Prime Directive, if you will)?

34. 34
Sam Denton

Ah, I found the USENET posting that I refered to earlier:

Also, they must have some kind of back-up bearings so that they can bring the main bearings down for repair and maintenance since even with low friction there will wear and tear that must be dealt with (OK, perhaps they could over-engineer the bearings to work for 20 years and then plan to shut everything down every 10 years…

Using scaling laws for bearing life, again from Rothbart, I get a design life of 125,000 years for the postulated main station bearing. Being big and slow helps a lot. Or we could subdivide the main bearing into ~1250 subassemblies, each with a discrete one-meter roller bearing. Now the design life drops to fifteen years, but we can easily swap out individual bearing elements for scheduled maintenance or emergency repair.

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Timoleon

I thoroughly enjoyed the article!
I do have a question involving acceleration and deceleration of the Ark. If the habitable cylinder is spinning to provide a sense of gravity to the arkonauts, wouldn’t the addition of force (acceleration or deceleration) perpendicular to the spinning bring about a nasty Coriolis effect? It would be dreadful to the max to be doomed to nausea or vertigo for 60 or 70 years at a time! It’s like the old sailing ship problem coming home to roost: afraid that you are going to die, and then afraid that you won’t! The only cure is to open the airlocks and jump ship!!

36. 36
Rob Knegjens

32. Gilgamesh wrote:Cryogenic freezing is impossible.

Impossible is quite a strong word. I won’t pretend to know anything about cryogenic freezing (and it doesn’t really interest me enough to spend the rest of the afternoon researching it) but a quick google search reveals that about 150 people have already been cryogenically frozen by one means or another immediately after death. Apparently water in the body is “somehow” replaced by anti-freeze to prevent cell damage, before the freezing.

32. Gilgamesh wrote:The terrestrial link (which is not realtime, it has several years of lag) cannot constitute a solution to react to unforeseen at the appropriate time. And I don’t believe one can be able to foresee *everything*.

I believe the human body is well enough understood to be kept alive purely under the supervision of machines. The additional complications would be in having to stock or somehow produce a large amount of intravenous drip. To this I have no over simplified solution:)

I agree we can’t foresee “everything” with respect to designing machines to keep both a hibernating human and a space craft alive. But would this really sway our decision to send the craft, especially if its relatively cheap to build? Surely arkronauts would be just as expendable as current day astronauts?

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Coofer Cat

A great article, and very thought provoking. Here are some of mine…

Firstly, over 700 years, the Arkonauts will doubtless innovate and create many things. On Earth, a good deal of that innovation has been bourne from wasting things (mostly natural resources). On board an Ark, waste is a serious problem (one which is mirrored here on Earth, and only recently becoming part of the common consiousness). One wonders about how Arkonauts could in fact innovate effectively without polluting their entire habitat, or using up significant propotions of their ‘natural’ resources.

This thought started when thinking about repairs. Some of the technology required for the Ark is pretty advanced for us Earthlings. All the resources of Earth struggle to make the Ark, so how would a fragment of the Earth be able to maintain it? To be terse, what will they do when the duct tape runs out? Here on Earth, the duct tape factory is somewhere very remote from us, and so able to do whatever it needs without disrupting our lives. I’m not convinced the Ark is realistically big enough to be able to support this (after all, they need things far more complicated than duct tape).

Another thought is about evolution. Over 700 years, it’s quite likely that a collony of humans could adapt to different gravities, oxygen supplies or any number of other things (maybe not to extreme athlete levels, but sufficient to live adequately). Thus, if one were to have an idea about the destination’s environment, one could ‘program’ the Ark to gradually mimic that environment over several centuries. On arrival, the “shock” of transition would be far reduced.

The ‘radio’ link with Earth in your ariticle poses something of a problem too. Whilst the bandwidth may be much like a currently available domestic broadband connection (pitifully small by the time the Ark launches, I might add), the latency will be nothing short of galactic. Without pre-arranging streams of data to be sent, it’s unlikely such a link would be much use at all. At 1 light year distance, the Arkonauts can ‘change channel’ with just 12 months delay. Whilst I’m sure something could be made of it, I’m not sure how useful this would really be (given 700 years of travel!).

Lastly, I would suggest that the Ark poses the best chance of success (meaning arriving at destination without some other event over-shadowing that arrival) if “there is no alternative”. That is, we humans tend to live by ‘college mentality’ which is to leave things to the last minute. Building the Ark because we expect some solar-system catastrophe to take place would (a) hurry it’s creation and (b) mean that those not on the Ark are doomed to death. Whilst this would doubtless mean a rather disproportionate number of politicians and lawyers on board, it would also mean that the endeavour of those of us left on Earth would not surpass the Ark itself.

That is, if Earth has 700 years of evolution and learning whilst the Ark is in transit, then by virtue of it’s relative size, it’s likely that we would build another, smaller, faster, better Ark and send that off too. Being smaller and faster, it would race past the original Ark, set up base camp and wait with bated, although smug, breath for the others to arrive.

This is a truly fascinating subject, made all the more realistic by some reasoned imagination. Keep it up!

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Themis

This is really a very fascinating article. Everything about the structure, collision, morale and possible overpopulation, problems are deeply thought out. However, I’m very curious about the societies structure. Is there an existing model, for a society like that of the ark? Is the education system supposed to entirely eliminate crime and social disorder? Will there be a legal system to enforce the rules, or a police force? There where other comments about a religion forming based on the ark. What about existing religions, and there cohesion in this environment? Five to ten thousand people will have many different ideals. Will there be limits on physical and genetic abilities, on the first crew leaving? What will be allowed and what will be forbidden? What are the taboos going to be, before this great ark leaves? What will recreation be, and what will work be? Will these people have full workdays, and if not, what’s going to keep them occupied, art, music, reading, education? Also, if Earth had a significant breakthrough in nanotechnology, or any important technological advancement, would the people of the ark be able to recreate Earth’s inventions? It would make sense that nanotechnology could supplement their immune system and protect them against foreign viruses / bacteria on a foreign planet, or even if one day they return to Earth. Also, as an ending thought, I was curious if there was any figure as to what the cost of such an undertaking would be. Thanks for the great article.

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Ruben D

“Homo Cyberneticus” is a plausible stage in solving this problem. Human beings uploading their essence into super computers. Transmitting our conscienceness into a storage system or artificial body based on self-healing nano technology. A race of robots that carry our minds long after our bodies have turned to dust. Mind “uploading” can probably be achieved in our lifetime and allow our “souls” to live indefinately within technological vessels. Perhaps our minds can be uploaded into living ships themselves. Unless there are blue screens in the future.

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TJ Miller

Something to consider - do we really need a habitable planet (or even a planet at all) at the destination? As long as there were sufficient resources (water ice, carbonaceous and iron asteroids, etc) at the destination system with which to construct colonies (in the fashion proposed by Gerard K. O’Neill et al), why should we even bother with a planet at the other end?

Consider this - the arkonauts would have already adapted to life in space colonies, and would have done so for at least a few centuries, if not millenium. They would already be comfortable with the idea of simply building their own habitats on a grand scale and living within them.

Reducing the requirements to just finding compatible stars (and even then this could carry a wide tolerance) should be sufficient, no?

/P

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Jon

“I won’t pretend to know anything about cryogenic freezing (and it doesn’t really interest me enough to spend the rest of the afternoon researching it) but a quick google search reveals that about 150 people have already been cryogenically frozen by one means or another immediately after death.”

There is a pretty obvious word in your post that puts a bit of truth in Gilgamesh’s points, death.

These people are DEAD- and have not been revived sucessfully.

No matter- I once heard someone compare humans to cockroaches- we’ll figure out a way to get to and live somewhere else, give it time.

42. 42
Great_Pretender

I like the idea of generational ship, but the resources and cultural differences (compared to Earth, after a few years) would be massive. Not that there’s anything wrong with cultural differences; it would be interesting to see. Technology would evolve in such a different manner, too.

But until we find a way to have an endless supply of resources (ramjets?), we’d have to settle for hibernation. And then the colony at Tau Ceti, or where ever you want to go, would have technology centuries old. When Earth develops faster than light drives, they’ll be having a big old laugh at the primative colonies.

The Bungie game Marathon involves this kind of thinking. I think a lot of the people on the ship were in stasis, while some raised families and the ship was primarily controlled by three artificial intelligences. And they made the ship out of Deimos, which is rather impossible for our time.

That game was set in the 2700’s (the Marathon was launched in the 2400’s). Hopefully we can set sail before then.

-TGP-

43. 43
Stephen Fuller

The people of a space colony will need something to do to give their lives some meaning. They should be kept busy building a backup space colony even as they start off to their first destination. They could inhabit both once it is completed, which will add some variety of places to explore.

They should try to collect raw materials along the way to keep adding modules, and once they get to their destination, and it turns out there is no suitable planet to terraform, they can keep collecting the materials that will make their colony sustainable so they can keep moving to new destinations as needed.

They may decide to upgrade to more powerful communications, or leave behind relay beacons in order to stay in touch with earth, or split the colony in two and go in separate ways but keep in touch with each other. That way, if one finds a suitable planet, the other can be contacted to follow. However, maybe the ultimate goal should be to expand the space colonies to a large enough size that planetary living isn’t really desirable anymore. (So much for the name Ark then.)

44. 44
Jean-loup

A solar sail would not have to take on board the braking fuel, as described in Rocheworld: when the ship needs to decelerate, a smaller sail and the ship can separate from the larger outer sail. The large sail focuses the light onto the smaller sail, which “applies the brakes”. I highly recommend Rocheworld. Its 40 years travel is much more convincing than the 734 years travel described here (even though I liked this article for its visionary aspect).

In answer to Hugues (20), it is indeed very likely that machines, more intelligent than humans, will make the the first trip to another star. We are currently unable to build anything that can do interstellar travel, but these machines smarter than us will be able to do it.

45. 45
Engineer

As an engineer, I’m concerned about the minimal complement of Arkonaut-Engineers required to sustain a level of technological micro-civilization.

Has any thought been given as to the ratio of complements between, oh let us say, artist, scientists and teachers?

1000 people is exceedingly small to recreate a microprocessor for repair/replacement.

Obviously, a well-equip workshop would be needed, but I should caution that some rudimentary form of technology should be the mainstay for simplicity and ease-of-repair.

K.I.S.S.

46. 46
Zolom

Can you imagine living in a world without sky?

Zolom

47. 47
Wim Coenen

The thermonucleoelectric propulsion mechanism sounds complicated.

Personally I like the idea of “project orion”, where you have a pusher plate + two stages of shock absorbers, and simply throw out fusion bombs behind you. The reaction mass can be built into the bomb. It sounds crazy but the numbers seem to work out. It even scales beautifully to huge “ark” vessels. And we already have all the technology!

48. 48
SUMMITMAKER

Actually, Cryo freezing is not needed at all nor freezing the body in any way. How about staying prefectly fit and doing the journey. If you think that by the time we start building this ark, be like 50 to 100 years from this post.. we would have already made VAST advancements in Biomedical Engineering to allow us to use our own stems cells to keep us clearly alive, youthful and functional throughout the entire trip. It would not be about several generations of life spans, but about one it would end up being more about population control then anything. Given that us humans are pretty attached to sex as a past time. Just google Aubrey de Grey or Live Forever

Also just think, once a human starts living beyond say 80 years average, you would not have generation gaps of intellect, no schools, no RELEARNING the system, so humans would start evolving to understand longer time spans, to deal with such a trip, this while procces would become easy and you would become smarter as the trip went on.

49. 49
Wesley Parish

Well done! I “drafted” so to speak, a design for a starship for a novel I wrote, in which the starship was an incidental and mysterious character appearing in the night sky of the inhabitable planet it was heading for, as a bright new star.

The major differences between my design and yours was I did have the fusion reactor setup in the midst of the starship’s spinning body. It was embedded in the fusion fuel, though, and also covered by a suitably thick radiation shield with the intention of breaking the ionizing radiation into ultraviolet, visible and infrared wavelengths. Which the fusion fuel then filtered further, before it reached the habitable parts of the starship.

I didn’t think of making the drive bidirectional - thanks for that! It does make sense, of course - you stack the fusion fuel at both ends. From the front, it shields the ship’s inhabitants; from the rear, it burns away as reaction mass. And anything that boils away, you can reroute to the front part of the starship to freeze up and get re-used.

As far as the size of the starship went, I thought fifteen kilometres wide would be too small for a spacefaring vessel, ditto for length, though I haven’t really figured that out yet. And according to Flannery’s “The Future Eaters”, 15 000 people is just on the minimum size for a survivable population - any less and it can’t sustain the inevitable losses.

Just my 0.02c worth - inflation these days!!!

50. 50
AsCii

Congratulations on the article! It seems to cover many essential aspects. Nevertheless, one that I would like a bit more of elaboration is the internal ecosystem of the ark and how to sustain it for 700+ years. Scientific experience shows that artificial closed ecosystems are difficult to sustain and unstable (much more for such a large one as the ark). More at Biosphere 2.
My opinion is that this is one of the major difficulties that will have to be overcome first of all…

51. 51
mux2000

Consider this:

By the middle of this century it will probably be possible to ‘upload’ the contents on one’s brain (or the ’scheme’ or ‘pattern’ of neural connections) into a computer, and run said contents on a ‘brain simulator’ software, running at some arbitrary clock speed.

Taking into account the miniaturization tendencies displayed by current tech it’s natural to assume such a computer running thousands (or more) of brains simultanuously, all living complete, fulfilling lives inside some immersive virtual reality environment, can be made very small and very light, reducing the requirements on mass, fuel and therefore travel time by orders of magnitude.

Taking into account the simulation could be run at a speed much slower than normal human brain activity, subjective travel time for our arkonauts could be much shorter than actual travel time (from whatever point of view), and we can even stop the simulation from running at all during the trip, giving us subjective travel time of zero (!).

The question then comes up of downloading the uploaded brain schemes into biological bodies on arrival at the new planet. I guess the tech for doing that is quite far right now, but I won’t be surprised if in a few decades an answer would come up for this as well…

52. 52
kto

I wonder why you didn’t mention Project Orion: is it because you’ve never heard of it, or because of something else?

53. 53
xantox

51. mux2000 wrote:

Taking into account the simulation could be run at a speed much slower than normal human brain activity, subjective travel time for our arkonauts could be much shorter than actual travel time (from whatever point of view), and we can even stop the simulation from running at all during the trip, giving us subjective travel time of zero (!).

If you stop the simulation, then you don’t need a simulation. If the argument is that travel is risky for biological bodies, then one should only clone the bodies at arrival, so that travel would be always subjectively instantaneous. Of course, the technology to do that would be so tremendously advanced that this approach, while pertinent in principle, can only be part of strategy 0. But Gilgamesh argument is slightly different, that is : the travel itself in the Ark is not necessarily a bad thing that one should need to shorten. If arkonauts still have a long-term mission, they would not care much in their daily life. Their life is in the Ark, and that would be already completely fulfilling. So the point here is the opposite : instead of simulating a brain, you are simulating an Earth.

54. 54
Gilgamesh

36. Rob Knegjens wrote:

Impossible is quite a strong word.

OK, “impossible” is maybe a little strong. Maybe that one day… But for the moment, people who get cryogenized are swindled, except of course if they are well-informed and that they want nevertheless to pass Styx river in the boat of Iceman . Obviously, swindled or not, the customer is not likely to complain…

36. Rob Knegjens wrote:

Surely arkronauts would be just as expendable as current day astronauts?

Expendable? Hey, but it is a humanistic project which I propose . In any case, there is always the question of the habitat when one arrives in the distant system. And this is seldom mentioned in sci-fi scenarios.

55. 55
Gilgamesh

36. Timoleon wrote:

I thoroughly enjoyed the article! I do have a question involving acceleration and deceleration of the Ark. If the habitable cylinder is spinning to provide a sense of gravity to the arkonauts, wouldn’t the addition of force (acceleration or deceleration) perpendicular to the spinning bring about a nasty Coriolis effect? It would be dreadful to the max to be doomed to nausea or vertigo for 60 or 70 years at a time! It’s like the old sailing ship problem coming home to roost: afraid that you are going to die, and then afraid that you won’t! The only cure is to open the airlocks and jump ship!!

Glad that you liked the article Timoleon There will be a radial Coriolis effect (while going from the Hub to the Floor), because of the structure rotation, but no such effect coming from the acceleration due to engine thrust (which is parallel to the axis of rotation). This represents a constraint nevertheless. An horizontal acceleration is not very comfortable, for this reason it is interesting to lay out the “continents” floating on an interstitial water surface. This one will take a dip because of the acceleration but the living spaces will be perfectly horizontal compared to the various components of acceleration.

Limiting acceleration, amax is given by the ocean dip which will cancel its depth on the shore located on the front.

amax = g.tan (Arcsin (x/L))
with
x = 25 m the ocean depth at rest
L = 10 000 m the Ark length (width of the ocean)

amax = 2.5 cm/s ².

Here one thus proposes an acceleration of 2 mm/s ² so there is some margin.

56. 56
Francisco Romero

Awesome article, fascinating.

Only, it can be a little low profile in intentions (well, its a bit of irony given the magnitudes in question! ). I remember an interesting spanish SF novel (”mundos en el abismo”, “worlds in the abyss” by Javier Redal and J. M. Aguilera); in it appear some huge vessels, the Juggernauts; the ark could be made into one of these juggernauts:

As it is very difficult to accelerate (and decelerate) the ark, why insist in decelerating? simply, once reached the desired travel speed, keep it (that would aleviate the problem Timoleon points: the ark must do some kind of change from “accelerating”/”braking” mode, when g is true aceleration, and “stationary” mode, when g comes from rotation. In Clarke’s “Rendezvous with Rama” the visitors must face that same problem).

The ark should have some few “subarks” (shuttles), much smaller, that, in the right moment, detach from the ark with some skeleton crew and a small (100 - 1000) criogenized population. It brakes for some 20 - 30 years and spends 10 - 20 preparing an habitat in the target destination. Then, they can accelerate again to catch the next ark (launched from earth 50 - 70 years after the first one) or they can stay in the environment and wait for the next shuttle(s) launched from the different arks to increase population and fill the created habitats. Sorry I can’t elaborate the concepts here…

The arks themselves would never stop, they will get their fuel (H to be breed to D or directly D) from the space, that is not completely void, and travelling at really high speed they would “reap” a sizable amount of material in multy century travels. They will use it to maintain speed, to steer to the next solar system (and finally some millenia after depart perhaps back to earth) and to accumulate fuel for the shuttles. That shuttles will provide with new population for genetic diversity and supplies and raw material when needed whenever the ark comes to a system populated previously from another ark.

The arks circuit would provide fisical communication (and ease data communication) between the different colonies and old earth much as the “juggernauts” maintain cohesion in the “imperium” of Akasa-Puspa in the Redal/Aguilera novel I cited before.

Earth would need to launch a new ark or two every century to start the ark commute and after two or so millenia, only to replenish the shuttles of the arks that choose to pass through the Solar System, the ark system would be then mostly self maintained except for the supplies of the shuttles (the fuel would be provided by the ark itshelf). By then, some other colonies would have a sizable population and give the human race the capacity to survive almost anithing.

Ten arks with 50.000 people each would be more individuals living out od the solar system than the largest estimated population of neanderthals at the peak of their evolution…

57. 57
Brent Van Dussen

Has the necessary radiation shielding necessary to protect biological inhabitants from cosmic rays been taken into account? I remember reading something in SCIAM a while back that several feet of concrete and or lead would need to be between man and space to provide the same protection that Earth’s magnetic field so readily provides? Is the idea that the ARK would be so massive that a few feet of concrete for a hull isn’t a big deal?

Great article and excellent commentary/response from readers/authors! I love sites where you can easily enter comments without having to create a new username and password

58. 58
Steve Bowers

Excellent work! Now that I have taken the time to read it all I can see your reasoning for each design decision.

A couple of points; the Daedalus design incorporated two stages; perhaps if your ship had a disposable first stage it might reach a somewhat faster speed.
Secondly the ship would need to provide energy for heating, lighting, life support, and food production for seven hundred years; have you calculated that? This is a large ship, and running costs would be considerable.

Finally the genetic diversity of the population could be kept high by taking a lot of DNA along in cold storage; either as gametes, zygotes, or even, perhaps, digitised (now that the genome has been mapped this could be a possibility sooner than you might think).

59. 59
Gilgamesh

52. kto wrote:

I wonder why you didn’t mention Project Orion: is it because you’ve never heard of it, or because of something else?

Yes, of course I know about project Orion.

But it is a project which seem more credible to me for the (ambitious) exploration of the solar system that for an interstellar travel. In particular, the specific impulse (Isp) is relatively modest.

The maximum effective specific impulse, Isp, of an Orion nuclear pulse drive generally is equal to:

Isp = Co · Ve/gn

where Co is the collimation factor (what fraction of the explosion plasma debris will actually hit the impulse absorber plate when a pulse unit explodes), Ve is the nuclear pulse unit plasma debris velocity, and gn is the standard acceleration of gravity (9.81 m/s2; this factor is not necessary if Isp is measured in N·s/kg or m/s). A collimation factor of nearly 0.5 can be achieved by matching the diameter of the pusher plate to the diameter of the nuclear fireball created by the explosion of a nuclear pulse unit.

For a bomb of 10 kt, Ve ~ 100 km/s. That is Isp = 0.5 × 1e5/9.81 ~ 5000 seconds. I’ve seen a paper about a H-B11 engine (with protons and boron-11 reagents) which had an Isp of one million seconds ^_^. It is such technological magnitude which should be reached.

60. 60
Dragolen

I think the more timely solution will be to create small unmanned probes using ion engines and solar sails to reach relativistic speeds and look for viable destinations before we worry about sending bodies out of the solar system. To create a ship capable to transporting large numbers of colonists, we have allot of challenges to get past first.

Our ship designs will have to cover the same protective parameters afforded by a planet if we are going to survive the crossing between stars. The one thing I have not seen mentioned is how to shield life from the solar winds without sacrificing a significant percentage of mass for shielding. Our magnetosphere is what keeps us alive, and would be worth duplicating. I wonder how powerful an electro-magnet would have to be to provide the same level of protection and if we could live near the generating magnets ?

And we face the prospect of a catastrophic impact. Even a grain of sand is a real threat to the Space Shuttles when it’s moving at 10000kph+ relative speed. Without sufficient long range sensors, a large vessel could be turned into ’swiss cheese’ by cometary debris. So we would need to create multiple layers of protection, with the ability to ’self seal’ after a catastrophic impact.

To maintain reliability, the best design I can think of would have the fewest moving parts: a sphere with solar sails designed to impart a small rotation seem to make the most sense. Add simple ion engines to power reaction jets, and the facilities to repair or produce new sails, and you at least have some redundancy. We have to go back a few centuries and look at what the early sailing ships were facing for getting around the world, and use that as a starting point.

Then you have to look at the crew: if this would be based on the ‘Star Trek’ model, we have a long way to go to getting everyone to get along sufficiently that they would not ‘chew their own legs off’ from being cooped up for almost a millennia. There is are biological reasons why teenagers rebel and seek to distance themselves that cannot be undone, so we must provide enough room for people to migrate around the ship. And managing the human element may be the most challenging aspect of an ‘Ark Ship’.

Personally, I’ll be pleased if we get some to Mars and back in my lifetime, and return to the Moon. I can still recall seeing Neil Armstrong set foot on the Moon, and it’s sad to think that we have done nothing as important as a space-faring species since.

D.

61. 61
Gilgamesh

50. AsCii wrote:

Congratulations on the article! It seems to cover many essential aspects. Nevertheless, one that I would like a bit more of elaboration is the internal ecosystem of the ark and how to sustain it for 700+ years. Scientific experience shows that artificial closed ecosystems are difficult to sustain and unstable (much more for such a large one as the ark). More at Biosphere 2.
My opinion is that this is one of the major difficulties that will have to be overcome first of all…

The relative failure of Biosphere 2 is due to lack of oxygen, because of lack of photosynthesis. Oxygen level dropped by 0.5% per month in its last year of operation. That year (1994) weather was particularly bad in Arizona. In the Ark, of course the amount of solar radiation is controlled.

Of course, controlling the ecosystem is crucial. But I do not think that it is *more* complicated when the ecosystem is large. It is rather the opposite I guess. Inertia is larger, the diversity of feedback loops too.

62. 62
Gilgamesh

44. Jean-loup wrote:

A solar sail would not have to take on board the braking fuel, as described in Rocheworld: when the ship needs to decelerate, a smaller sail and the ship can separate from the larger outer sail. The large sail focuses the light onto the smaller sail, which “applies the brakes”. I highly recommend Rocheworld. Its 40 years travel is much more convincing than the 734 years travel described here (even though I liked this article for its visionary aspect).

Hello, there is a version “with sail” of the Ark… But it is difficult to compare the philosophy of Prometheus and that of the Ark. The vessel proposed by R. Forward is sized 20 x 67 m, and much less for the crew area.

A representation here:

Quite simply, I do not see how to carry out a travel without return in a so small livable volume.

63. 63
Gilgamesh

46. Zolom wrote:

Can you imagine living in a world without sky?

True, the sky is not blue; but it is turned blue by the thickness of the atmosphere. And on the other side, one would see the “antipodes” at very high altitude, like the sight from a plane. When I try to imagine it, I feel a rather imposing image…

64. 64
Gilgamesh

40. TJ Miller wrote:

Something to consider - do we really need a habitable planet (or even a planet at all) at the destination? As long as there were sufficient resources (water ice, carbonaceous and iron asteroids, etc) at the destination system with which to construct colonies (in the fashion proposed by Gerard K. O’Neill et al), why should we even bother with a planet at the other end? Consider this - the arkonauts would have already adapted to life in space colonies, and would have done so for at least a few centuries, if not millenium. They would already be comfortable with the idea of simply building their own habitats on a grand scale and living within them. Reducing the requirements to just finding compatible stars (and even then this could carry a wide tolerance) should be sufficient, no?

Very right TJ, that is exactly the concept of the Ark: small bodies first. And a stellar spectrum of good quality (with a tolerance of less than 1000°K).

No absolute need for a telluric planet with atmosphere. And nothing says that there is one on Epsilon Eridani.

65. 65
Gilgamesh

40. Brent wrote:

Has the necessary radiation shielding necessary to protect biological inhabitants from cosmic rays been taken into account? I remember reading something in SCIAM a while back that several feet of concrete and or lead would need to be between man and space to provide the same protection that Earth’s magnetic field so readily provides? Is the idea that the ARK would be so massive that a few feet of concrete for a hull isn’t a big deal?

Protection against radiation is indeed not mentioned in the article, which relates to the general *philosophy* of the project (where there is already much to say).

But engineering cannot stop there, obviously . Solution against radiation also allows to solve another fundamental problem: *how to cool the Ark*? The Ark is a thermodynamic machine: its hot source is internal, and its only cold source is space. Without too much detail (useless at this stage) I calculate that I expose internal surface to a luminous flow of 350 W/m ² (i.e: 1 terrestrial luminosity, taking into account albedo, distribution of energy on the sphere and nocto-diurnal cycle). This is roughly the luminous portion in terrestrial ecosystems. Part of it is used directly to light the Floor, a part at the heart of the vegetable strands. It is necessary to evacuate this energy into space, which cannot be done only by radiation, so that it is necessary that Ark’s skin reaches a sufficient temperature.

Say P the specific radiative power of surface (in W/m ²).

$P = \sigma T^4$ ~ 350 W
$\sigma$, Stefan’s constant = 5.67 x 10-8 W K-4 m-2
$T=\sqrt[4]{\frac{P}{\sigma}}$
T = 280°K ~ 7°C

I thus need a surface temperature of about 5-10°C. A little more if only a part of it radiates. Let’s say 13°C, that is what I found in an old calculation.

It is thus necessary to build a fluid circulation (probably water) between the hot floor and the cold skin, in order to maintain a sufficient radiation temperature.

The idea is to organize a gravitating circulation, while taking advantage of the water density when its salinity increases: hot water with salts is denser than cold water without salts. This can be calculated precisely (I could try to find the calculation) and that gave a pressure differential of about 1 bar.

This is an old version (sorry, in french) going back to March 2006. The ocean was 60m by then, now I limited it to 25m.

The question is: how to concentrate salts, then desalinize this water? To concentrate sea water, the first solution one may think is by evaporation (and represented in the diagram), but, calculation made, it is the least possible one, considering the required flow, it would be necessary to transform the Ark into a giant grill. For now I don’t have a solution, but just some tracks.

- biological solution: fibres extract water and concentrate salinity
- physical solution: using double walls to form precipitations.

This is because it can also allow to solve another “old” problem: to make rain into the Ark. The idea is to use the engines and the double wall of the sides. In this idea, the driving cycle does not stop after the 30-40 years of acceleration. A residual thrust is maintained (this would also maintain knowledge of the engine mechanics over secular durations, not bad!) in order to push alternatively one thickness then the other. When pushing on the internal wall one increases the open space which separates the internal wall from the external one, which creates a depression. An oceanic water surface put in contact with this vacuum evaporates and saturates the double wall with vapor. Then one pushes on the external wall, and compression expels saturated vapour in the Ark’s atmosphere, vapor in which are mixed ofsalt microcrystals supporting nucleation. So that in my idea, it could rain. It is only an idea. I do not have yet any calculations about it.

The other idea, more anecdotic, is to carry out a very light movement of precession of the Ark (by slightly decentring the thrust of the revolution axis) in order to make the structure “dance”, destabilizing the oceanic water mass, which would make it possible to recreate a periodic artificial tide.

In any case, the idea is well to make everything function like a thermodynamic machine in equilibrium, with the minimum of pumps and valves, and using the engine thrust in an intelligent way. Once again, the structure dimensions oblige to find natural operations, worthy of an alive structure functioning over very long periods.

In short, I manage to desalinize my water and I return from there to the problem of cooling: we have a so-called *thermohaline sinus* which separates the last strand layer from the skin itself. The ocean is approximately 25 m thick, and the wall is as much thick, in a medium at 5 bars pressure. At this depth, there is a layer of circulating salted hot water at the beginning, in contact with a skin produced by the perimetric wall. It is necessary that this skin is at the same time thick and conductive.

- If it is too thick or not conductive enough, the Ark is condemned to thermal death. The vegetable fabric as a whole is resistant but rather insulating. The idea is to imagine some pilosity, in the form of a relief, a little like that of a tire, in order to increase the radiant surface. Moreover, I imagine that the one should be able to inspect the outside of the walls. In the hollow of the relief furrows, one arranges light aluminum footbridges (the floor in direction of “Great Outside”) whose crossing through the skin would form a “thermal bridge”. Finally, one can imagine that the wall, by forming the skin (by apoptosis, or cellular death) integrates light metal atoms improving conductivity of materials.
- if it is not thick enough, it cracks under the pressure (not so high but nevertheless). To set an order of magnitude between predicted conductivity and needed resistance, for a temperature of radiation of 13°C the skin would need to be 80 cm thick. It is impossible to imagine a free external layer (detached from the remainder of the wall). It must be connected to the wall by “tendineous” pillars maintaining it in place. Moreover, “sinusic” space must be opened to human intervention, therefore have a minimum thickness of 2 m.

The thickness of this layer of sub-epidermic water is small, but its role is strategic, somewhat comparable to terrestrial atmopshere.

66. 66
ChirpingBirdy

Why not use the moon as the ark?

/Chirp

67. 67
Gilgamesh

66. ChirpingBirdy wrote:

Why not use the moon as the ark?

Because the Moon is a really huge body! The mass of the Moon represents about 2 944 000 000 Arks So, you also need about the same mass of fuel to move it.

68. 68
Gilgamesh

Dragolen, lot of things in your post.

60. Dragolen wrote:

I think the more timely solution will be to create small unmanned probes using ion engines and solar sails to reach relativistic speeds and look for viable destinations before we worry about sending bodies out of the solar system.

A relativistic velocity starts at about c/10, and if one keeps below of c/5, the Tsiolkovski formula remains valid: v/ve = log (M0/M). If we want that M0/M remains within reasonable limits, it is necessary that ve, the fuel ejection velocity, be definitely higher than v. For ionic engines, the ejection velocity is about 30 km/s, or c/10 000. That is really very far from relativistic velocities. Moreover, the ejected gas (currently xenon) must receive an energy which it does not produce itself (contrary to chemical fuel which is a reaction product). The ionic engine is interesting only by using solar energy, transformed into electric tension by photovoltaic panels, so as to create electric or magnetic fields able to accelerate the ions in the conduit. In other words, if we look at energy, it is a solar engine. One cannot make use of it to be propelled far from a star, or at least, one can only provide in such way an impulse. The ionic engine is interesting on the other hand to travel into the luminous fields of stars, thanks to its very high Isp (compared with chemical engines). For the solar sail, it is the same thing. The additional interest resides however in:

1. The engine (the sail) is extremely light;
2. It is really possible to reach relativistic velocities, because the “ejected gas” is light itself, bouncing on the surface and transmitting its impulse to the sail.

In this way one escapes elegantly from Tsiolkovski’s “bronze law”. A surface (almost) as light as one wants, can reach (almost) the speed which one wants. The starting impulse can be enough, on the other hand one does not have any more energy when one is far from a star… If one agrees to embark only an extremely reduced payload, for which the energy requirements are weak (some sensors, a radio antenna..) during the coasting flight, then it can go. Therefore, OK for a solar sail probe (but no ionic engine).

60. Dragolen wrote:

The one thing I have not seen mentioned is how to shield life from the solar winds without sacrificing a significant percentage of mass for shielding. Our magnetosphere is what keeps us alive, and would be worth duplicating. I wonder how powerful an electro-magnet would have to be to provide the same level of protection and if we could live near the generating magnets ?

The electromagnet is an “active” solution, requiring a working technology and energy. This is why I prefer a “passive” solution of a liquid layer (sines and the ocean itself, which have also other purposes).

60. Dragolen wrote:

And we face the prospect of a catastrophic impact. Even a grain of sand is a real threat to the Space Shuttles when it’s moving at 10000kph+ relative speed. Without sufficient long range sensors, a large vessel could be turned into ’swiss cheese’ by cometary debris. So we would need to create multiple layers of protection, with the ability to ’self seal’ after a catastrophic impact.

I must decide myself to try a probabilistic calculation for such kind of collisions (it is not complicated, but one needs precise astronomical data).

The Ark leaves the solar system (the Oort cloud where comets come from) at reasonable velocities (a few hundreds km/s). At the coasting velocity of 4 500 km/s, a risk exists only for centimeter-sized bodies (if they are smaller, the front shield is enough to cover). But bodies of this size, or bigger ones, should have no chance to exist outside a stellar system. They are produced by aggregate of dust in the systems in formation, as far as we know.

60. Dragolen wrote:

To maintain reliability, the best design I can think of would have the fewest moving parts: a sphere with solar sails designed to impart a small rotation seem to make the most sense. Add simple ion engines to power reaction jets, and the facilities to repair or produce new sails, and you at least have some redundancy. We have to go back a few centuries and look at what the early sailing ships were facing for getting around the world, and use that as a starting point.

Rather than a sphere, a cylinder. A sphere in rotation cannot yeld an uniform gravity. For a manned vessel with a solar sail, the problem is the payload, which need to be *extremely* low, and the energy which one need to produce when the vessel is far from a star. I never managed to obtain a viable solution of the kind, even with very optimistic calculations. Beyond a certain mass of the sail, it becomes a limiting factor.

One finds in the literature values such as 0.1g/m ² of solar sail. I calculate kind that in daylight, beyond 0.3 km ² of sail per kg of payload, one reaches an asymptote and that one does not exceed 0.38 ly per millennium, with a coasting flight at end of the acceleration of just 115 km/s, which is quite low. One thus needs an extremely powerful laser thrust (requiring vast quantities of fusible materials: deuterium, He3, etc) because the Sun alone is not sufficient at all.

60. Dragolen wrote:

Then you have to look at the crew: if this would be based on the ‘Star Trek’ model, we have a long way to go to getting everyone to get along sufficiently that they would not ‘chew their own legs off’ from being cooped up for almost a millennia. There is are biological reasons why teenagers rebel and seek to distance themselves that cannot be undone, so we must provide enough room for people to migrate around the ship. And managing the human element may be the most challenging aspect of an ‘Ark Ship’.

We are certainly not going to take as a basis a model of society proposed by the accounts of science fiction, which feature restricted groups and support pathological situations, for the needs of creating drama. Let’s forget all the science fiction books, to start.

We need to look at human history, the true one. Are human societies able to keep a moral objective over a millennium duration? Yes. Religions, for example, are a proof of that.

60. Dragolen wrote:

Personally, I’ll be pleased if we get some to Mars and back in my lifetime, and return to the Moon. I can still recall seeing Neil Armstrong set foot on the Moon, and it’s sad to think that we have done nothing as important as a space-faring species since.

That is sure… but this means that one should set reasonable objectives.

What ?

Yes, yes. The ark *is* a reasonable objective.

69. 69
ChirpingBirdy

Still think the moon makes the most sense if the Earth was facing destruction and we really did need an ARK to save our species. It is close and it size would be an asset.

Any one know where Commander John Koenig is?

^_^

http://en.wikipedia.org/wiki/Space:_1999

^_^

/Chirp!

70. 70
Chester12

Gilgamesh is concerned that only 5 to 10 thousand people will be
able to leave Earth on the Ark. Do you really think that all 6.5 billion
humans - and who knows how many more by the time such a craft
is built - are worthy or needed for such a mission and journey?

Be honest, we have way too many people on this planet as it is,
most of them subsisting off those who make actual contributions
to society. This is a fact, not a cruel remark.

I hope those who truly make a difference to humanity and
the world can change things for the better. Otherwise we
must spread out into the galaxy or face extinction.

71. 71
Gilgamesh

69. ChirpingBirdy wrote:

Any one know where Commander John Koenig is?

Space 1999, cult classic!

Strategy S0 is exactly like it. It is necessary to start from this root: a childish desire, invaluable, delirious, and vulgarly adult by the solutions which it proposes.

Then these children grow. One day, they want to tell *true* stories. Even if they happen in the future, they are grown up stories, which one can also tell to the children.

72. 72
Gilgamesh

70. Chester12 wrote:

Gilgamesh is concerned that only 5 to 10 thousand people will be able to leave Earth on the Ark. Do you really think that all 6.5 billion humans - and who knows how many more by the time such a craft is built - are worthy or needed for such a mission and journey?

I use the word “ark”, which has deep meaning, because I’m “Gilgamesh” not because I’m “Noah”. In its Epic, Gilgamesh wants to reach immortality. The history of Noah is different, it consists in saving humanity from a forthcoming destruction. In both cases they wish to save lives, but one is wondering what one could do better than to live, and the other one, what one should not make worse, as it is at least necessary to survive.

It happens that many people think that indeed, humanity is promised to forthcoming destruction. And they are afraid of that (which can be understood). So that the word Ark may express the idea that if one does not make it, then all remaining left is to live like mummies on a failing Earth or like cockroaches in a dustbin planet. For me, as I am not afraid that humanity could destroy itself, neither in the one, nor in the other way, and which rather see it blossoming, the Ark is not at all “the last hope of humanity”. It is, on the contrary, the most ambitious of its projects to come, the one which the grandfather could show to their grandsons in the night sky: “you see, the star which shines, there? It is the Ark”. And live this vision.

Only a trustful humanity, alleviated about itself and curious about the world, could give birth to an Interstellar Ark.

For this reason there are just 10 000 people in the Ark. If humanity manages to set up this immense project, these thousands of people would represent the champions of this humanity carrying the hopes of all the others, not some “happy few” succeeding the escape from hell.

73. 73
jc

Excellent writeup and commentary. But no one seems to mention money or credit while traveling/living on the ark. What would the economy be like? How do people buy stuff? If we’re using earth funds, will it be the euro or dollar or something else entirely? Much as I would like to believe Star Trek’s take on money, I would side with Star Wars take since it seems more plausible. A better question would be how does economic work on the ark?

74. 74
AsCii

Since I see so many enthusiasts for this idea (including myself;) I have a proposition to make that has been in my mind for quite some time now.
Why not start a Wiki based site for the Ark project. In this way, any people will be able to put forth his propositions in the right place which can be evaluated by scientists from all over the world who are interested…!
There can be sections with the various problems that we are facing and each one can be dealt with seperately!
What say you??

75. 75
Steve Bowers

Could you describe where the 21 gigatonnes of fuel are stored? Is the fuel kept on the outside of the rotating drum? The acceleration fuel could be kept in separate tanks to the deceleration fuel, and the acceleration tanks jettisoned when the ship reaches interstellar speed.

It would be helpful to me when I am trying to envisage the craft in three dimensions.

76. 76
Centauri Dreams » Blog Archive » Envisioning the Interstellar Ark

[…] Strange Paths offers a robust essay on the topic of interstellar arks, one that considers our future among the stars without warp drives or other breakthroughs that get us past the speed of light barrier. Star Trek and its ilk offer familiar, short-term travel analogous to our own relatively brief journeys in the Solar System. The real thing may be different. […]

77. 77
AsCii

jc wrote:But no one seems to mention money or credit while traveling/living on the ark. What would the economy be like? How do people buy stuff? If we’re using earth funds, will it be the euro or dollar or something else entirely? Much as I would like to believe Star Trek’s take on money, I would side with Star Wars take since it seems more plausible. A better question would be how does economic work on the ark?

I don’t think that any economy inside the ark would be of any positive value. What would money be good for? Everyone will be able to have whatever he/she wants (and is accessible). First and most important example: food. No need to pay for it since there is enough for everybody. Next, there can be a predefined quantity for every good that the Ark can supply for the arkonauts. You can also imagine that not all people will want everything. e.g. you might like chocolate, I might not! Now, as for other commodities (e.g. how about a nintendo wii? ) these can be publicly accessible from everyone!
In any case, my opinion is one strongly against any form of currency or other form of economy. The size of the Ark makes it possible to exist (maybe even better as a community than other here in Earth) perfectly, I think, with the system I described. I cannot imagine any problem that it wil create.
In the opposite case, however, I think that a series of problems will emerge:
1) On what basis will the salaries be decided.
2) Everyone will seem to be “blocked” to their salaries. Someone with a low income will be virtually doomed to stay there = inequality
3) How will the money be circulated to the system?
4) etc…

78. 78
David Staum

Fascinating article!

However we must first ask ourselves, what is the purpose of such an ark?

Exploration?

If so, robotic missions will suffice, especially as virtual reality technology continues to advance. In a few decades, or a century at most, a virtual experience may be well near indistinguishable from actually being there, other than having a real-time effect. The propulsion technologies described in the article can be applied much more easily, without having to worry about the frailties of human life and of the mass required for them or for their artificial biosphere. Robotic missions could also be accelerated far beyond human tolerance, sending results back perhaps within a human lifetime. It is far easier to explore our galactic neighborhood via our robotic surrogates.

Survival of the human species?

There are two scenarios that could conceivably result in the eradication of humankind and its entire works. One is for our sun to go supernova and destroy the entire solar system. In that case, the ark would indeed be necessary. However, that isn’t predicted to happen for several billion years at least, long enough for our species to have evolved into something entirely different, or to have completed its natural life cycle.

The other, more immediately likely scenario is for our own planet to become uninhabitable, due to thermonuclear war or massive environmental catastrophe.

That would, however, leave our solar system intact. Therefore, far more important than launching an interstellar ark, is to begin work towards settling our own system. We can explore the feasibility of terraforming Mars or even some of the Jovian satellites (despite the distance from the sun, a thick atmosphere may create a sufficiently strong greenhouse effect.) Underground habitats can be constructed with surface lenses that allow sunlight to be magnified into the interior and for agriculture to flourish.

Planetoid bodies aren’t the only option. Asteroids can be hollowed out, filled with an atmosphere, and spun for artificial gravity. Habitats can be constructed from scratch and placed in solar orbit.

We have the vast neighborhood of our own solar system to explore and settle, and we can do so without cutting ourselves off from the rest of humanity and without taking an unimaginably long time.

79. 79
Suki

cryogenics:

There is that species of frog that freezes solid while it sleeps during the winter, and there is the fat tailed lemur (madagascar?), the only primate that hybernates… so we have proof of principal in both directions. But why send whole people, if they’re not going to be doing anything on the way? Maybe for moving around a solar system on the cheap, or for shift change on a generational ship…

cybernetics:

I doubt the idea of simply scanning the brain and uploading it to a computer will ever work so smoothly, I think the closest we’ll ever get is just adding more and more electronic upgrads, slowly merging with them, slowly having them play more and more important roles in our thinking that eventually it will happen to someone that their last biological parts die, and they don’t even notice.. I think once we do a little more we’ll see how blurry the line between our ‘wet ware’ and artificial neural network chips can get.

economy:

obviously for essentials like the biosphere, the condition of the ark, they will have to share. everyone owns it and relies on it, vote to make collective decisions on how to manage it. ( off topic: who mentioned the inertia of a biosphere, that’s a really good explination )

I imagine that many people will be involved in the workings of the ark (in fact why not give everyone a “station job”) but there will be room for luxury, room for individual choice and expression, you need to include some system of trade, or it will develope on it’s own. I think it would be very important to, somehow (??), set it up to prevent anyone from becoming rich, to keep a class system from developing…

One system i thought up ( while watching a friend play worlds of warcraft ) was to distribute ‘loot’ (which really belongs to everyone in the party) by having people bid, giving the object to the winner, and distributing the amount paid by the winner among everyone in the group. this works a lot better than distributing things by dice rolls…

so wether it’s buying the rights to some hydroponics plots for a number of years, or the unallocated ‘birth rights’, or the surplus power from the ’sun’, or the production from one of the assembly plants, or some of the raw materials being reclaimed by the recycler I think it could work.

another idea I’ve always found interesting is what the results would be of having a fixed amount of currency in the system, I mean, in so many respects it is a closed system, why not close the economy. It sortof gurantees against inflation. or manage the currency the same way you manage the other resources: it belongs to everyone. I see two ways; distribute all new money equally between people, then inflation sortof produces a negative interest. Or increase/decrease everyone’s cash by the same percentage, (for no *real* effect, it just changes the numbers you have to deal with).

Time frame:

The same scenario plays out over and over, the situation with us and the sun’s other orbiting bodies now is just like europe considering colonizing north america. This shell is getting near it’s limit or exploitation, let’s break open another. The same thing will happen again, we’ll fill up the solar system then start looking for the next, we’ll fill up the galaxy eventually, and we’ll jump across to the next…

The Civilization Game series is funny, direct from earth to alpha centari. Really you’d have no reason to start a project like this until the closer islands are full. In fact I see that as the way to build this thing in the first place, by the time you’re in a position to consider a project like this I imagine there would be countless asteroid mines that have evolved into orbital cities much like the planned arc, over time invest in fule, add some engines, make some structural adjustments and you’re good to go. Operation as normal, except now you ‘re making your own sun. Once you arrive, start new colonies on all the small bodies in the new system, soon they’ll start taking off on their own in new directions.. like von numan probes, but I’m sure by that time we’ll have them working for us too..

and I would think that the inter-stellar internet will involve a lot of “I bet they’d like to see this”, but I’m sure some of the details will be worked out while building the inter-planetary internet..

contaminating the universe with humanity!?
what good is the universe with noone around to appreciate it?
and besides, it’s no different from evolution down here, if you have less children for one reason or another, it’s just more room for mine. if you don’t you will be replaced by someone who will.

80. 80
Gilgamesh

75. Steve Bowers wrote:

Could you describe where the 21 gigatonnes of fuel are stored? Is the fuel kept on the outside of the rotating drum? The acceleration fuel could be kept in separate tanks to the deceleration fuel, and the acceleration tanks jettisoned when the ship reaches interstellar speed.

The best, is to have no tank at all!

On the two Ark diagrams (the plan and the complete drawing) you can see that the corollas have some thickness. That is the fuel, in the form of *hydrogen ice* on a thickness of approximately 600 m (density: 70 kg/m3). Its temperature must be maintained lower than 14°K, and initially, it is necessary to isolate it from the powerful solar radiation (if not, one would obtain a Tex Avery gag . But it would keep in the form of ice, without need for pressurized tanks.

There is a whole story about the engines. I could invite somebody in this discussion (Lambda0). He does not agree completely with me on the need for breeding. Rather than to breed one can indeed imagine to extract Deuterium and Helium3 from Neptune, which has vast amounts of them and where the gravity well is not much deeper than that of the Earth.

But if we use helium3, then tanks are needed…

81. 81
Randy Black

Thanks for the essay. Fascinating problem and a setting that has intrigued more than one science fiction writer. The potential degeneration of colony civilization, including the consequences for the travellers and the Ark, offer endless opportunities for problem-solving by would-be physical and social engineers, not to mention ethicists and philosophers. One scenario: Computers, artificially intelligent and as ruthless as HAL, would become the teachers, police, and probably the Gods of the Arkonauts. Of course if we wait a hundred years, or even 50, advances in artificial intelligence, robotics and biology might remove the need for human parents of the Lander Generation. Frozen embryos of all species, including humans, would rely on robotic wombs, midwives, nursemaids, teachers, and trainers to raise them to maturity at the destination planet. The Robotic Ark would require less mass, have more options for terraforming or further exploration, could use native materials for production, and would not risk the lives of thousands (or imprison generations). Robots could populate an entire world with plants and animals, and even build houses, vehicles and industries, ensuring New Earth was truly an Eden, before bringing humans into it. Talk about deus ex machina! Not as interesting as the classic Ark, though.

82. 82
Chris Wren

Wonderful article, thank you!

83. 83
Michael Dunkel

AsCii wrote:I don’t think that any economy inside the ark would be of any positive value.

Communism doesn’t work on Earth, I don’t see why that would change three million miles away. Obviously the unique situation on the arc would require some special planning and treatment, but nevertheless a few circumstances would lead to the establishment of a bustling economy on the Arc:

The Arc would be large enough to have it’s own raw materials and support it’s own industry. It will be able to grow crops, trees, etc. There would concievably be large stores of non renewable raw materials. Companies/individuals could bid for the use of these materials, submitting proposals for what they would do with the materials. Recycling would allow the same batch of materials to be used repeatedly. Similar bids could be placed for blocks of land, or anything really, to be leased for a period of several decades or something like that.

This kind of blends into this next point, that you have an Arc that would initially be filled with the best and brightest people, pulled from what would undoubtedly by millions of applicants the world over. The subsequent generations would be raised knowing that they were isolated from Earth, that they would need to be self sufficient and hard working in order to keep their society alive and running, and cope with any hardships that would inevitably arise. This would lead to more hard working and enterprising people.

Even if the initial crew complement was solely enough to run and maintain the vessel, the plan Gilgamesh laid out involved a growing population, and very reasonably so. This means that as the population grew there would be extra labor force, either the work force will be used inefficiently, there will be unemployed people who, while cared for, still have nothing to occupy themselves, or there will be extra nonessential industries that crop up. Not to mention that even the initial population should have excess crew, because if there were not enough arkonauts to fill up all necessary positions, with plenty left over for other pursuits that means that you have no flexibility, and that would doom the vessel. If you only have enough crew (or anything) for a best case scenario, how are you going to adapt to an emergency situation.

My last point would be the low availability of resources. While this may seem to contradict my first point I would like to stress that although resources will be available, they may not be plentiful. Certain luxuries will not be available to everyone, and there is no getting around that. If all the current luxuries were made universally available someone would invent some new ones to set people apart. People will have the desire to obtain these goods and there will be “money” to be made providing it. I think that denying this is denying human nature, and that an Arc would be unsuccessful if it did not provide the ability to fulfill this aspect of human nature, even if it provided for the physical needs and replicated the ecology of earth, sending it up without a working economy would be asking for trouble.

Here are some example industries that could crop up. Entertainment such as amusement parks, movie theatres, professional sports, concerts, manufacturing of instruments, designer clothes. Candy, meat (expensive and very impractical in a small isolated ecosystem, yet oh so delectable). This isn’t even considering competition among the various fields. I can understand wishing that the future did not hold designer clothing, but I see no evidence pointing to such a Utopia.

84. 84
lambda0

I suspect that the problem with breeding deuterium is that we don’t have enough neutrons. The global reaction, including the main branches is :
6D -> 2He4 + 2p + 2n
The reaction T-T has a much lower cross section compared to the other, and T will react with another D nucleus before. The global reaction burns 6 D and produces only 2 neutrons. Of course, with a fine tuning of the temperature and density, it may be possible to increase the probability of the most interesting branches, but I don’t think that this will change much the situation.

On the other hand, it seems to be “much” easier to collect the deuterium from the atmosphere of planets like Uranus or Neptune. In fact, the NASA has already studied ramjets that could fly in the atmosphere of such planets to collect also helium 3.

The first idea (breeding) is a physics problem that may have no practical solution, the second idea is basically an engineering problem, and some have already imagined credible solutions.
I think that the credibility of the project is improved if we avoid too strong hypothesis on the physics, even for a very far term project.
But the idea is not new : those who are a bit familiar with interstellar flight litterature will remind that Daedalus, the interstellar probe imagined by the British Interplanetary Society, was supposed to be fueled in helium 3 from the atmosphere of Jupiter.

Another remark is that if we are able to build a fusion propulsion system that is capable to accelerate a multigigatons interstellar ship to 5000 or 10000 km/s, the thrust and the few km/s necessary (for smaller ships) to escape from the attraction of a planet shoudn’t be a problem. In fact, the propulsion system of the ark is based on a reactor imagined by Bussard 15 years ago, and Bussard also described some high-thrust variants adapted to high gravity environment. Most of the work of Bussard was confidential when we started this discussion with gilgamesh (almost 2 years ago), and very interestingly, Bussard presented his last results at an astronautics congress in Valencia, last October :
You can notice that in theory, it can work with a variety of fusion fuels, in a wide range of specific impulses, compatible with high gravity applications (such as collecting fuel in the atmosphere of planets), or with high specific impulse applications, such as interstellar flight.
This is exactly the kind of propulsion that may one day push a ship to the stars. If it works…

85. 85
4EE&

Gligamesh, great article!

I would offer three good reasons to go now, or, start now on that journey.

The Earth is a fragile nest. We are one large Earth Crossing Asteroid away from utter extinction. Since we don’t know if other intelligent beings exist, it makes sense for us, as a species, to ensure our survival –if for no other reason than doing so will let us continue to look for someone else.

There is a Superpower transition taking place. The United States is fading as a civilization –as much as it pains me to say so. China is ascending and living through the transition (the next 50 years) is going to be dangerous for mankind as a whole.

The definition of “Human” is likely to change very soon. The knowledge and technology necessary to change the very essence of what it means to be “Human” exists today. Since we don’t know where the path of changing the human gnome will take us, it would probably be a good idea to have a pristine sample available –such as it is.

Since the Sun is headed off in the general direction of Vega at 20kms anyway, why not go thattaway? And wouldn’t we have to overcome at least some of that momentum in order to get to Epsilon Eridani?

The problem with Vega is it’s the wrong kind of star (Spectral class B9 vs. our own G4). What that means is you’d have to be 9AU away from it to survive. I’m not suggesting it isn’t possible or even a good option, just a little scary. Of course, compared to a spaceship built by the lowest bidder on a contract, it’s probably not so much…

Not far off the right tangent is a G class star called HP93017. It’s almost 50ly away, but, I’m an optimist.

The point of all of this is that there a lot of important things to consider and we should do something sooner rather than later.

Many thanks.

86. 86
Gilgamesh

74. AsCii wrote:

Why not start a Wiki based site for the Ark project. In this way, any people will be able to put forth his propositions in the right place which can be evaluated by scientists from all over the world who are interested…!

AsCii, I think that it is an excellent idea, which also was suggested on another forum. I will try to set up a Wiki, but that will take a little time, and I am beginner in this field

87. 87
reflash

The fuel requirements for deceleration will be less than that for acceleration due to the fact that some of the fuel will have been used to accelerate the ark. Wouldn’t that reduce the total mass of the ark?

88. 88
The Interstellar Ark « KuiperCliff

[…] February 23rd, 2007 Thanks Rian, for sending me this link to an article on Strange Path. It’s a theoretical piece about the ‘Interstellar Ark’, a manned mission to colonise another planet. It’s a particularly long and comprehensive look at the construction, design and habitat of the Ark, and addresses all manner of considerations necessary for a successful project. The conclusions are, roughly, that a gigatonne spaceship, constructed partly of regenerating organic material, would take about 700 years to reach a viable star system. It would be populated by an initial compliment of two thousand families, living in a 300 square kilometer surface on the inside of a massive rotating cylinder. It could be propelled by a photonic sail, pushing the living environment ahead of it. Nothing is left to chance in this piece, with energy requirements, target worlds, social structure, breeding policies, etc, all looked at from a technical and philosophical perspective. […]

89. 89
Gilgamesh

87. Reflash wrote:

The fuel requirements for deceleration will be less than that for acceleration due to the fact that some of the fuel will have been used to accelerate the ark. Wouldn’t that reduce the total mass of the ark?

It is true that one needs less fuel for braking, as the Ark is by then less massive. But at the same time, one needs much more fuel when accelerating, because we also have the fuel needed for braking . And that is *very* expensive! On the whole, it is needed to square the Tsiolkovski exponential giving the ratio of departure mass over dry mass.

$[exp(v/v_e)]^2 = exp(2v/v_e)$

On the other hand, your remark allows me to be more precise in respect to what is simplified in the article. If one considers equal engine, therefore constant thrust, then the acceleration phase must be longer than braking. But that does not change the mass in any case.

90. 90

A very fascinating and thought-provoking article. It does an excellent job of describing “realistic” interstellar travel (as best we can understand it within the current context of our knowledge). Except (in my opinion) for one thing: the notion of shipping live meat across interstellar distances.

In space travel terms, human beings are an extremely inefficient way to “deliver intelligence” to a distant location in space. The vast bulk of the ship’s non-fuel mass (radiation shielding, artificial ecosystem, volatiles, rotatable cylander, etc.) is needed to sustain human bodies, which in turn support human brains, which constitute a relatively small fraction of their mass. If human brains were absolutely necessary, it would be far more efficient to ship “brains-in-vats” living in a Matrix-style simulacrum of a ship or a planet, with cloning machines to produce new bodies if/when they were actually needed upon arrival.

However, I see no reason that human brains will be necessary. As I recall, Kurzweil predicts that, given Moore’s Law and developing technologies like quantum computing, it will be possible to purchase a computer with the processing power of a human brain for \$1000 in 30 years or so.

Even if his forecasts are over-optimistic and it takes, say, 100 years, that’s still a lot sooner than we can expect an interstellar ark to be built. Provide these computers with evolutionary algorithms and some form of automated manufacturing with which they could replicate themselves (3-D printing or nanotechnology), and they would be able to evolve themselves. Even if they were only as smart as housecats, they could outperform humans in space in all respects.

They would be much more compact and efficient (in terms of “intelligence per kilogram”) than human beings. Current “dumber-than-insect” machines already are. Humans have not left Low Earth Orbit in 30 years and have no actual, in-process plans to do so in the future.

To send a human into space, you must also send a “slice of Earth” with her–atmosphere, radiation shielding, climate-control, food, water, recycling/waste disposal, etc. A machine does not need a “slice of Earth.” Space is its natural habitat. No corrosive oxygen atmosphere, no water. Give it some solar panels or a plutonium power source and it can just go on “living” for many years without needing to intake new resources.

The Cassini mission is a great example of why machines will inherit the stars. If we tried to imagine a manned Saturn mission, with a huge nuclear-thermal rocket-powered ship constructed in space, big enough to keep a few hundred or thousand pounds of human meat alive for several years (with all of the psychological and relationship challenges humans would face), the costs and challenges would be utterly prohibitive. Yet, the unmanned Cassini probe gets us data about as good as a crewed “Battlestar Galactica” would.

Humans possess only two advantages over machines: intelligence, and the ability to reproduce (colonize). Computer power doubles every 18 months, while human brain power doesn’t double at all except perhaps in Evolutionary Deep Time. This means that, inexorably, the human “intelligence advantage” is rapidly fading. By the time it becomes feasible to build a human-carrying “Battlestar Galactica” sufficient even to get past Mars, there will almost certainly be cybernetic intelligences equal or superior to the human mind.

Humans might make it to Mars–mainly because we already have the technology and resources to do it now, if Bill Gates and Warren Buffett wanted to do it bad enough, and got together with Burt Rutan and Robert Zubrin. Mars is (barely) Earthlike enough that humans could “live off the land.” Less hospitable environments (for humans) will become habitats for machines (perhaps bearing “uploaded” human minds). Again, machines already “own” translunar space. They become more capable every year. Humans do not.

Cybernetic (machine-based) “colonists” have major advantages over biohumans, some of which have already been mentioned. They would be able to slow their “clock speed” to make the journey subjectively short, or even instantaneous. In a crisis, they could radically increase their clock-speed to give themselves plenty of time to develop a solution. They would not be limited to the snail’s pace of mere human reflexes.

They could even maintain a communicating interstellar civilization by radically slowing their clock-speed in concert so that a message requiring a hundred or a thousand years of transit time could arrive (and be replied to) in a subjective instant.

Such entities might also have a much wider range of stars to choose from, since all they’d need is a source of “gray bodies” and a sun capable of powering solar cells or a Jovian planet with a powerful magnetic field they coul tap for energy by electrical induction. They would not need to search for something approaching “Earth-normal” conditions.

I do think the idea of a plant-like “grow-able” bioship is an intriguing idea. Perhaps a “molluscoid” bioship (with an enclosing, protective shell) could be another option. Instead of carrying a crew, the ship (equipped with a sentient cybernetic “brain” and a fleet of small ships in place of “hands and tools,”) could be the traveller.

“Humans” may go to the stars, but (in my opinion) only by merging with our cybernetic progeny and evolving beyond the “meatbag” stage.

91. 91
xantox

I don’t share your belief that “human meat” is less efficient than anything else even remotely known in order to support an human being. Also, “mind uploading” is deeply outside our current technological horizon, so that it belongs firmly to strategy 0.

However, the goal of Gilgamesh humanistic dream is apparently another one. As mentioned in reply to comment 51, the goal is not to deliver intelligence to a distant location, nor to exchange data, nor to bring the gift of life to exoplanets (which don’t care much about it), nor to get there as quickly as possible.

The goal is to let men and women (and not different creatures) understand their environment to the point of rebuilding a World. So that in the road towards stars one finds himself ending up rebuilding worlds, and one who is building worlds is no longer into a road towards stars, he is into a road toward himself. This is what brings all the excitement and greatness of such travel.

92. 92

We are a lot closer to human uploading than to the ability to grow/build gigaton fusion-powered spaceships in space. We already have implants that allow a paralyzed person to control a computer (in a somewhat rudimentary fasion) with his or her mind. We do not have fusion power.

Machines have already replaced humans for all space exploration beyond LEO, even at their current extremely limited degree of intelligence. I think it will prove easier to adapt ourselves to space (upload and/or gengineer “living spacesuits” as part of our bodies) than to adapt space to our current form (build giant O’Neil colonies and Arks).

Considering the vast expense involved in an interstellar travel project, it does not seem likely to me that we or our descendents would ship humans to the stars (with all the extra expense, effort, and danger that involves) as an end-in-itself, just to make a “humanistic” statement. By the time we’re in a position to build any realistic interstellar spacecraft, we will probably hav greatly revised our concept of “human” to include the “different creatures” who do go.

Genetics, nanotechnology, robotics, and AI are advancing a lot faster than rocketry, fusion power, and technologies for building mega-structures in space. It’s a race between “Singularity,” which is supposed to happen in our lifetimes, and the construction of giant fusion-powered starships, which (apart from radical lifespan-expansion or mind-uploading) will be a project of our distant descendents. I’m pretty sure “Singularity” will win even if the estimates of 30-100 years are over-optimistic.

93. 93
xantox

Even assuming optimistic estimates (however, the implants which you mention are far more rudimentary in respect to mind uploading than a thermonuclear bomb is in respect to controlled fusion power), that would only modify the -engineering- of the project, that is, instead of building a World within a physical environment, one would build a World within a simulated environment with some advantageous physics, but one would still have to dream and build that same World.

If your mind is uploaded into silicon structures, and unless you want to live inside a Hell, you also need a simulated body. You need simulated families, friends and societies. You need simulated environments, trees, seas and houses. So that the problem of “uploading” a single mind becomes suddenly quite vast.

While these environments would be engineered differently, their design could be similar, so that the simulated living structure could well end up again like an Ark. The dream of Gilgamesh could not vary by a single bit by having it simulated, though as suggested in comment 1, there would be the further advantage of increasing the variety of Worlds which could be explored.

94. 94

[…] An excellent post on the theoretical and practical considerations involved in the construction of a “interstellar ark” generation ship here on Strange Paths. […]

95. 95
Gilgamesh

There is nothing which opposes theoretically to human uploading but that does not means that we are close. I’m personally following the lesson of the neurologist Antonio Damasio (Descartes’ Error, The Feeling of What Happens, Looking for Spinoza).

Biological consciousness, so far as we know, is built on a body, a self, without which there is no viewpoint and nobody who thinks. An intelligence, it is initially a thinking self, not the faculty to solve an equation.

It is also not a question of computing power, and Moore’s law is in my opinion not adequate to reveal us at which rate consciousness could come to machines.

To build biological consciousness one needs initially a structure able to represent the state of each part of the body. These charts are interactive, they define each one a sensomotory state of the part. The whole of the chart is then integrated in order to make an unity of this diversity and which will become the entity to which all thoughts will refer. And this state shall be developed so that any action will have a tropism moving away from negative stimuli and approaching closer positive ones. This does not result from a predefined program defining canonically what is pleasant and what is not, but from internal determinism born from the growth of continuous interactions with the body state, and finally forming an interface with the environment.

Each of these parts (brain, nerves, sensors, interior medium, muscles…) shall be itself directly “involved in the business”. Being formed of living organisms, each element will have its own tropism, its own “sighs of ease” and “cries of alarm”. The integration of all these signals will give rise to an integrated and elaborate driving reaction, emotion. At this stage, one has a core-consciousness, that which one at least suppose in Vertebrates.

As the brain charts the body (again, interactive charts, constantly signalling the body and regularly treating responses) it gets images of external objects, through what the senses (sight, hearing, smell, touch, proprioception…) deliver. The body charting allows synthesis of objects which become in their turn conscious units (built-up objects presenting in unitary form to consciousness, which is able from a simple starting effect, for example a color, to make re-appear memory of associated percepts). Coffee, is the vision of a cup or a coffee machine, a noise of the streaming liquid, the touch of the cup handle, the particular ability needed to seize the cup without touching the hot parts, the heat towards face when lips are approached, the bitterness of the first mouthful, etc. Each element is not sufficient to represent the richness of the concept but may be sufficient to make re-appear memory all the others.

Once again, the concept is not formed if it is not fully developed. Coffee, it is happiness of the morning or what concludes an harmonious meal, unless it joins insomnia or tachycardia. It is inevitably linked to some specific pleasant or unpleasant experience, according to surrounding circumstances. Because at this stage we are not at the point where one could call upon human consciousness in a snap. This comes from the animal kingdom and the concept is there because it is useful there. The word ‘concept’ is besides improper, because it implies intelligibility of the object, which is not yet the case. Concept is not yet defined (through language) but it is already acting as the integrated image from senses. And the object may represent any lived phenomenon and not just outside objects.

Starting from these first level charts (body, object), a second level chart allows to represent the Self (the body) like it was causally modified by the object. This representation is not an external point of view, it is for Damasio the flow of Consciousness itself, impossible to put at a distance. According to Sartre, any consciousness is consciousness of something. One can try to describe this something as being the Self perpetually seeing itself in interaction with a causal object, be it a memory, a tooth ache, a lamp posed on the desk. The tonal modes of this causal relationship Self-Object is Feeling.

After this discussion, which brings us only to the beginning of human consciousness, the conclusion that I draw here about the birth of an artificial intelligence is that the diagram thus traced from emotions to feelings does not let us conceive a thinking machine which would be also insensitive.

One can of course imagine that its corporeity would not need to walk in green grass. That could be interesting. But it would be in any event a person which we should care morally just like an human being. If not, it is not humanity which is going to stars. It is just a probe which tells us what it found, “it” being nothing but some sensors.

And in any case they would be other individuals, and not us. The Ark wants to answer one question: how let us - us human beings - live ourselves autonomously in outer space. It is not because other machines could do it, possibly better than us, that we would lose the desire of it. These are two independent things.

96. 96
Chris Wren

“And in any case they would be other individuals, and not us. The Ark wants to answer one question: how let us - us human beings - live ourselves autonomously in outer space. ”

Precisely. Even assuming we ever develop the capacity for uploads (and that’s an enormous if, the upload is just a copy of you - it is not you. YOU live out your life here on earth and die, while your copy gets to experience space travel. What’s the fun of that?

In any case, sentient uploads aren’t going to be a matter of mere computational power. The highest resolution photograph of an individual remains a photograph. Similarly, an upload of a human mind will remain simply a lifeless image of that mind, without the complex gestalt of interactions, environmental stimuli of which the living mind is a part. If you want to create the equivalent of a living human consciousness, you need to simulate the world.

97. 97
Keko

1. Chris Wren wrote:Even assuming we ever develop the capacity for uploads (and that’s an enormous if, the upload is just a copy of you - it is not you. YOU live out your life here on earth and die, while your copy gets to experience space travel. What’s the fun of that?

I agree that it is a big if, but I disagree with the rest. If uploading and running a consciousness is possible then this means that consciousness and experiencing arises from information processing. So if you can create a copy of the information that is you and build a machine that is capable of processing this information as your brain does then your copy is not to a lesser extent you than the original. This is the very nature of information. Therefore, depending on how you define “you” with regard to elapsing of time, either both the original and the copy are you or neither of them.

2. Chris Wren wrote:In any case, sentient uploads aren’t going to be a matter of mere computational power. The highest resolution photograph of an individual remains a photograph. Similarly, an upload of a human mind will remain simply a lifeless image of that mind, without the complex gestalt of interactions, environmental stimuli of which the living mind is a part. If you want to create the equivalent of a living human consciousness, you need to simulate the world.

Yes, that belongs to the big if. If it is a matter of resolution and if the uploading device is not capable of a perfect copy then this means we are not really uploading the complete consciousness. But I do not think it is necessary to simulate a world in order to run a consciousness if consciousness arises from information processing. All we need to do is to attach some sensors and I suppose a radio link to earth would be enough. Just imagine a poor guy that is completely constrained in a space craft unable to see or sense anything tactually, just listening to a headset. I think he will still have consciousness. However, I am not saying it is moral to do that with a machine that has consciousness.

98. 98
xantox

Keko: yes, copies of men and women are men and women. The disagreement on this point further to comments 90 and 92 was rather in regards to “sentient Arks” and other forms of intelligent beings which could be in some way better suited than men and women in order to explore outer space. For your second point, you should consider that the poor guy is not someone who was forced in such position, but someone who choose to go. Now, supposing -you- wanted to go, would you choose to go without a body, alone, closed into a sealed coffin? Some sensors and a radio link (which will fail someday) already provide a world, though quite limited, and probably not sufficient to avoid madness. Also, if one would be “uploaded” as an adult he would bring its past world with him, it is not like he was -born- in the void.

99. 99
reflash

To Keko,

I think that what Chris Wren was getting at in the first point (IMHO) was the fact that, even if we can do a sentient upload, the copy would experience the space travel, unless we were able to download the experiences to the original person the copy was made from. I don’t really see any way of doing that with the time frames involved.

The amount of power required (and the sheer mass of data) to transmit it back to Earth would be prohibitive, to say the least. Not to mention interference, etc. that would degrade the signal.

The original YOU that the copy was made from (even assuming a perfect copy) would not be able to access the experiences of the copy unless those experiences were somehow united with the original conciousness.

100. 100
Keko

1. xantox wrote:yes, copies of men and women are men and women.

That is not my point in comment 97. Chris Wren claimed that there is no fun for you by exploring a distant place with an uploaded copy since the copy is not you. I think that is wrong. The copy is you - given that consciousness arises from information processing, which is an essential precondition for uploading. Therefore, uploading would be a way for a human consciousness to explore a distant solar system. The described ark would not be a way, since only ancestors would reach the system. And in my opinion, the consciousness is what matters. If uploading is available then it should be favoured. In the long term the colony on the ark might even evolve into another species, since the living conditions are necessarily a little different from earth. The beings would adapt to a new environment. This is not very different from creating devices that carry our consciousness.

As far as we know no miracles in physics have to be discouvered to make uploading possible, although our knowledge about the mind and consciousness is quite limited. Thus uploading does not belong to S0. However, I also believe that building an ark is easier than uploading.

For the second point, as was mentioned in comment 90, it could be possible to stop the information processing until arrival. After that there should be enough to experience and to do. A simulated world is not really necessary. However, I also see no reason not to provide one.

101. 101
Keko

1. reflash wrote:The original YOU that the copy was made from (even assuming a perfect copy) would not be able to access the experiences of the copy unless those experiences were somehow united with the original conciousness.

The experiences do not need to be transmitted back and united with the original. Yes, the original YOU that the copy was made of is not able to access experiences of the copy. And at the time the copy is made, the original is also not able to access experiences that the original will gain afterwards on earth. At this point it is crucial how you define “you”.
For the original before the copy, both the original after the copy and the uploaded being will be the YOU (or neither of them depending on definition).

102. 102
xantox

100. Keko wrote:

Chris Wren claimed that there is no fun for you by exploring a distant place with an uploaded copy since the copy is not you. I think that is wrong. The copy is you - given that consciousness arises from information processing, which is an essential precondition for uploading.

Yes, that is correct. I was merely restating for clarity of the discussion that, despite Chris agreement on previous comments, his argument was in fact forking away from them.

100. Keko wrote:

Therefore, uploading would be a way for a human consciousness to explore a distant solar system.

This is certainly an option, but uploaded humans will need uploaded worlds, in order to avoid living in a hell just for the sake of the experiment (cfr comment 93). This whole dream is about creating worlds and expanding the horizons of our consciousness, not reducing them. Be these worlds Arks engineered in vegetal structures, or computational Arks taking advantage of different physics, one will still need some Gilgamesh to dream and design them.

100. Keko wrote:

As far as we know no miracles in physics have to be discouvered to make uploading possible, although our knowledge about the mind and consciousness is quite limited. Thus uploading does not belong to S0. However, I also believe that building an ark is easier than uploading.

No miracles in physics are needed, but miracles in understanding our mind are needed. Just like one cannot forget the wall of special relativity, one cannot forget the wall of complexity. Blindly reproducing brain maps or evolving a simulated DNA would still not imply mastering the engineering of a civilization uploading (and not to speak about the required computational power and its reliability). To locate and arrange the correct degrees of freedom, understanding is needed.

100. Keko wrote:

For the second point, as was mentioned in comment 90, it could be possible to stop the information processing until arrival. After that there should be enough to experience and to do. A simulated world is not really necessary.

Cfr also comment 53, one goal of the project is also to live autonomously in outer space, not only to get to the target planet and colonize it. The planet could be a new Earth for some, and a fuel station for others which would be leaving again. While a simulated world is not a technical requirement if the persons are dead during travel and resurrecting at arrival, the point is that we build or simulate a world not because it is a technical requirement, but because we desire it.

103. 103
Steve Bowers

I would say that eventually, all feasible different strategies for interstellar travel will be considered seriously, and they may all be used. Future humanity would be ill advised to limit itself to simply considering one method.
Here is a page I put together describing four major concepts;
http://www.orionsarm.com/ships/Colony_Ships.html

The methods described are
Methuselah ships; ships containing a few long-lived individuals if such life-extension is in fact possible
Hibernation Ships ships with frozen or otherwise preserved but inactive individuals if possible (here I refer to K Eric Drexler’s idea of ‘biostasis, nanotech devices prolonging the life of non-frozen but inactive humans)
Generation Ships As described in Gilgamesh’s excellent essay, but perhaps with a smaller breeding population backed up with preserved genetic material
Data-only Ships ships with uploads or other forms of AI on board (if possible).

I think it is important to realise that the next few centuries might bring advances in many fields, particularly biology, while spaceship technology itself might quickly reach fundamental limits due to well-understood physics.

104. 104
Gilgamesh

100. Keko wrote:

As far as we know no miracles in physics have to be discouvered to make uploading possible, although our knowledge about the mind and consciousness is quite limited. Thus uploading does not belong to S0.

Admittedly, we conceive that our mind results from known laws of physics. But what S0 indicates, are in fact solutions which simply cannot be discussed, apart in saying: “when it will be possible, then…”.

It is sort of like a patent. A patent is a solution which can be explained to a qualified person, so that there is something to discuss concerning the operation of the object. I cannot register a patent allowing to paint one red blood cell out of two in blue, so as we can look purple, as I don’t have any solutions to propose. And I cannot get it registered by saying that I will do it with a “nanorobot painter”.

Science fiction is not science, and the great SF authors who also introduced new ideas in science were scientists. It is not astonishing. They wrote under constraint, like as for poetry. Poets like words, their forms, the rigour of their assembly, and it is when they master this grammar that they can imagine new forms, simple, which seems from now on obvious, because carried by the necessity of language.

To take an example in physics, special relativity is much more “simple and obvious” that Jules Verne’s Space Cannon towards the Moon.

What do we know about human mind? At the same time very little, and much more than simply 20 years ago. We start to see articulation of cerebral zones. We start to partly understand their functions and what they communicate. But we do not know, really not know, how one goes from an exchange of electrochemical pulses to something like “a feeling”. We are in front of an opaque Wall. Quite opaque for the moment. Admittedly, we can today bet that there is nothing else than alive cells which communicate. And since living beings are well established within the limits of Physics, reproducing this on another support appears “theoretically possible”. And I think that it will be done. But is it meaningful to seek to create now a “world” of which we know well that we ignore everything, starting from the essential of its nature and its laws? A chemist in a world without water, who would synthesize one milligram of H2O in its test-tube could deduce its molecular weight, its bond angles, interesting considerations about hydrogen bond. But would he simply imagine the color of the ocean under the sun? Waves and foam on the shore? The power of a cyclone and its elegant geometry? A tempest of hail ? A sparkling snow mantle? A glacier flattening the side of a mountain? An icefield tormented by the currents? Or simply the dawn? In short, a water world? No. He would miss, to resume, “complexity”.

For the mind, we are able to synthesize the microgram (the electrochemical pulse) and we know what “the ocean” (the thought) resembles. Compared to a water world, we start to say that water is soft or salted, solid or liquid, perhaps gaseous, and to detail the large oceanic basins and the principal rivers. But recreate a water world! No, we are well, well far from it.

105. 105
Keko

xantox, Gilgamesh: Yes, I agree with you in all respects. My different opinion was a result of the anticipated purpose of the Ark. If the purpose is to build a comfortable world outside of our solar system, be it earth-like or simulated, be it stationary in another solar system or between the stars, then all of your arguments are completely sound. I had more of an exploration and accomplishment idea in mind.

104. Gilgamesh wrote:Admittedly, we conceive that our mind results from known laws of physics. But what S0 indicates, are in fact solutions which simply cannot be discussed, apart in saying: “when it will be possible, then…”.

I see. So I got the meaning of S0 wrong. I did not mean to say that we are anywhere near the capability to upload. Instead, I just wanted to place uploading between the ark and some triumphant Physics. I think that uploading is actually much harder (maybe impossible) compared to building a working ark, but far more likely than instantaneous travel by miracle Physics, which is in S0.

106. 106
Gilgamesh

105. Keko wrote:

xantox, Gilgamesh: Yes, I agree with you in all respects. My different opinion was a result of the anticipated purpose of the Ark. If the purpose is to build a comfortable world outside of our solar system, be it earth-like or simulated, be it stationary in another solar system or between the stars, then all of your arguments are completely sound. I had more of an exploration and accomplishment idea in mind.

I think that we are well in the attitude of considering all the possible different ways. I am trying to create a “Wiki” website whose topic would not be centrally the Ark, but “autonomous life in outer space”. Capacity to live without a mandatory bond with Earth, the “cradle”. That could be entitled “Constantin’s (Tsiolkovski) Dream”, which would also make a nice echo to “Centauri Dreams” . The inhabited interstellar travel constitutes for me the result of such a process, as the seed disseminated by a matured fruit.

105. Keko wrote:

So I got the meaning of S0 wrong.

It is not your understanding of S0 which is wrong, it is probably the definition of S0 which should be refined. In principle, which arises from S0 are in fact all the the ideas which, within the discussion of targeting distant objectives or autonomous life in space, bring to a solution by the means of sort of Seven-League Boots, by means of ad hoc assumptions. They imply inevitably a part of subjectivity and personal judgement. That depends on what each one believes within the field of possibility in - say - a millenium. I propose already this practical threshold as a definition: 1000 years. All that is not realizable within this delay is automatically “S0” . The idea is that the man who will take the first possible way and what is discussed is the way of carrying out the first way towards stars, or to conclude the first project of autonomous live in space. If not, as the discussion concerning uploading shows it well, that does not only relate to theoretical physics but to the whole field of sciences: biology, neuroscience, nanotechnology…

So is uploading part of S0? In my appreciation yes, but it is only my appreciation of possible progress of science in the millenium to come. Nobody can claim authority on such appreciation, it seems to me.

That brings us to an answer to Steve, i.e. the link with science fiction:

103. Steve Bowers wrote:

http://www.orionsarm.com/ships/Colony_Ships.html The methods described are
Methuselah ships; ships containing a few long-lived individuals if such life-extension is in fact possible
Hibernation Ships ships with frozen or otherwise preserved but inactive individuals if possible (here I refer to K Eric Drexler’s idea of ‘biostasis, nanotech devices prolonging the life of non-frozen but inactive humans)
Generation Ships As described in Gilgamesh’s excellent essay, but perhaps with a smaller breeding population backed up with preserved genetic material
Data-only Ships ships with uploads or other forms of AI on board (if possible).

I quote the homepage:

* hard science
* plausible technology
* realistic cultural development
* vast setting
* 10,000+ year timeline
* no humanoid aliens
Thousands of years in the future, civilization spans the stars, and humanity has branched into myriad directions. Godlike ascended intelligences rule vast interstellar empires, while lesser factions seek to carve out their own dominions through intrigue and conquest. And beyond the safety of the human-friendly worlds, adventure awaits those prepared to risk all.

Let’s say that even in this “hard science” point of view, the program is still too vast for me. I am interested only in the first step around the cradle. If the Galaxy would be 100 m in diameter and 5 m thick, the playground of Orion’s arm would represent say a zone of the dimension of the Galaxy thickness (5000 x 5000 x 5000 ly) that is 100 m3 on that scale.

I am interested in just one cm3 of stars around the Sun

And the same for the technical solutions. It is less imposing, I know, but there are nevertheless lot of things to discuss. Also, I do not have at all the same vision of catastrophic events to come which would plunge humanity in the type of crises exposed in the timeline of the site. I do not believe that one can predict the future, but I think that when one risks a prediction, the only data one has to analyze, is our past. For me, we are still essentially men of the Neolithic era, sedentary beings which have lived of agriculture, with a division of labour allowing a technical progress. Our political practices are derived from what was invented in the Mediterranean basin 2500 years ago, and which were disseminated worldwide for the last 500 years. One does not change his own nature like a snap and I have a rather conservative vision of our own future.

107. 107

I agree with all of you that it would be cool if, centuries from now, unmodified bio-humans launched themselves to the stars. I would be proud of us. I just don’t think it is a likely scenario.

From one angle I can see how building a multi-gigaton interstellar rocket would seem to be easier than creating a posthuman AI or uploading human minds into cybernetic substrates. We already know how to build rockets. Except for the fusion power and the closed-cycle environment system (artificial world), we could start on the Ark today, if we were willing to commit a sizeable share of the global economy to the task. We don’t know how to upload human consciousness or build sapient AI’s.

However, there are two factors I think will prove more important than our current state of knowledge: technological advancement, and economics.

One of the major premises of the article is that we know enough about physics to say with considerable confidence that space travel 500 years from now will be done the same way Newton and Goddard taught us: by throwing stuff out the back of a rocket at high speed.

We cannot say with similar confidence what the state of computer technology, nanotechnology, genetics, medicine, and robotics will be then, except that (barring the adoption of some catastrophic failure-mode that destroys our civilization) they will be far, far more advanced than what we have today.

Except for a few new tricks like better construction materials and fusion power, the science of rocketry is complete. It will always be expensive and potentially dangerous to accelerate a pound of material to extreme velocities. As long as we’re using rockets, a low-mass payload will always have an enormous advantage over a high-mass payload of similar mission utility when it comes to actually getting financed and launched.

The technologies related to consciousness-uploading and/or sapient AI are all advancing rapidly, with no comparable “final end” in sight. The average game console contains more computing power than was available to NASA for the Apollo program. Not only is the hardware better by orders of magnitude, so is the software in relevant areas such as simulating a world. Look at the high realism of PS3 and XBOX 360 games.

In terms of rocketry and manned space, we have less capability now than we did in the Apollo era. Others here have pointed out that neurology has advanced quite a bit in the last 20 years. We’re still flying the exact same spaceships to Low Earth Orbit that we were 20 years ago, with no real prospect of an improvement. Burt Rutan and Virgin Galactic offer some hope for the future, but in a race between galloping “GNR” (Genetics, Nanotechnolgy, Robotics) technologies and snail’s-pace manned rocketry, I expect GNR to win hands down.

Back when Arthur C. Clarke and Stanley Kurbrick gave us 2001: A Space Odyssey, they provided the “obvious” answer to the question, “How will we explore the outer planets?” We’ll build a huge rocketship carrying men and an intelligent computer!

It turns out we didn’t even come close to sending men, and we didn’t even send HAL. We sent his primitive ancestors mounted on probes as small as we could make them. This may have been less “fun” than manned missions to Jupiter and Saturn, but it was also economically possible. Our probes, rovers, and other machines continue to become smaller, lighter, and more capable. Astronauts don’t.

Even though Clarke’s estimate for the development of sapient AI turned out to be wildly over-optimistic, we’ve made alot more progress in the direction of HAL than we have toward giant ring-shaped space-cities and huge manned space-cruisers.

Manned space exploration has always been mostly ceremonial. We sent men to the Moon to beat the Russians and show off American technical prowess. Once the Russians conceded victory in the “Space Race,” we left the Moon, maybe forever. We continue to piddle around a little in LEO, but again, I see this as ceremonial.

If NASA were to fire all the astronauts and do everything with probes and satellites, it would “look bad,” as giving up on a manned future in space. As long as they send astronauts up to the ISS once in awhile, the government can pretend that 30 years from now we’ll have a real space-faring civilization–like they’ve been doing for the last 30 years.

All real space exploration is done by machines, and I don’t see this changing in the foreseeable future. While we hope that 30, 50, or 100 years from now people will go beyond LEO again, machines continue to become more capable at an accelerating rate, neurology comes closer and closer to giving us the ability to interface the brain with machines and reverse-engineer the human brain.

The technology of implanting cybernetic interfaces in human brains and nanotechnology are both beginning to produce real, if rudimentary progress. 100 years from now, or 500, those technologies will have reached a much more advanced state.

I think a “gradual replacement” scenario (in which cybernetic implants and/or nanobots are introduced into the human brain, allowing the person’s consciousness to gradually migrate to the new substrate with vastly-expanded intelligence and calculating power so that the bio-brain may be transcended entirely) will probably be the path taken rather than making copies of human consciousnesses that exist simultaneously with the unmodified bio-human.

No matter how it takes place, it will always be more economically feasible to send machines into space than humans. As machines become more advanced and more “humanlike” in their intelligence (then becoming genuinely “human,” then trans-human) the economics will continue to weigh more and more heavily in their favor.

500 years from now (or whenever we or our descendants get around to building an Ark) it will be far easier and cheaper to launch a crew of cyber-intelligences and their simulated world in a package the size and weight of a PS3, than to send gigatons of soil, water, plants, animals, and people.

This may be less “fun” or less “inspiring” to us bio-humans than the thought of people just like us going. However, I do not think our descendants will be any more willing to pay several orders of magnitude more for a mission so it can be more fun and inspiring (i.e. meet ceremonial/emotional needs) than we are now when it comes to our missions to Mars, Jupiter, and Saturn.

This may sound pessimistic; however, if Kurzweil is right and we get something like radical life-extension, uploading or “gradual transition” from bio-mind to cybernetic mind within our lifetimes, then it could be us (what we grow to be in succeeding centuries) rather than our distant biological descendants who get to go.

108. 108
Gilgamesh

Your vision of the future is perfectly rational and argued and I agree that if the traced tendency is continued (success of the probes, cost and relative uselessness of the inhabited missions), things go rather in the direction of a robot-like exploration of space. Today, I agree completely that it is better to send 100 probes than an inhabited mission!

What could reverse the tendency in a near future would be democratization of space and development of leisure space stations in orbit. These could initially concern a small number of persons, but if it becomes lucrative to send people in space (while remaining close to Earth of course), then tendency could reverse and with it the search for new solutions allowing to satisfy an increasingly large number of persons.

109. 109
Blogcoven » Blog Archive » Analysing our future in Space

[…] Analysing our future in Space The vision of humanity departing this planet for one in a far-flung planetary system is deeply ingrained in any of us who have read or watched Science Fiction. In presenting his* analysis, Gilgamesh has demonstrated quite effectively the almost-maddening scale required to conduct any sort of viable interstellar travel. He puts the mass of the “Ark” in the order of Gigatons, which is pretty big, but still not on the serious planetary body scale. […]

110. 110
Dan Dx

I suppose that everyone here knows Asimov’s “Foundation”. Otherwise I summarize: The Galactic Confederation is in crisis, on the way to burst and sink in a new Middle Age. A group of scientists, under the leadership of Hari Seldon, undertakes to gather in various secret places (the Foundation) the whole of human knowledge and to try, thanks to the “psycho-history”, to foresee the evolution of the society, the crises which it’ll pass through, the means to be implemented to solve them.
Throughout the novel (3 volumes initially, then 2 sequels), whose action proceeds over several centuries, one follows the birth and evolution of various crises, the intervention of the Foundation to solve them.
The argument of this novel relates to a whole humanity spread in the whole Galaxy. The techniques of history forecasting worked out by the Foundation have to treat a complex object with galactic dimension. In comparison, our algorithms of weather forecasts would look like children’s games.
But, let’s imagine a project “à-la Hari Seldon”, applied to an object such as the Interstellar Ark and its population. The ultra-determinism of Asimov’s “psycho-history” is no more that absurd: the number of variables (technical events, breakdowns, diseases, social crisis, etc. as well as the various possible solutions and parries) is reduced to a reasonable size and manageable while putting many people at work on it, why not in a co-operative project “à-la Wikipédia”. The computing power would be provided by an alternative of seti@home! (#74 AsCii)
Ready? Hari Seldon, here we are!

And then?… Because may be one day, they’ll be real descendants of ourself, locked up in a real ark, subjected to a real form of social organization which we’ll have imagined from now! Will it be a social organization of the Ark looking like a remake of the Platonic Republic, with philosophical tyrants ruling the mass of the travelers and every aspect of their life, under the requirement of the single Article of the Fundamental Law “Thou shalt listen to the Ancients, if not, be careful with your ass!”? Will the so-called “Ancients” have alone a total access to the “World of Ideas”: the database of the “Interstellar Ark Foundation”, established before the departure, including all Wikis and HowTo possible and imaginable: “Culture of Cress For The Lame”, “Protected Use of N2O Gas in Case of Riot”, “Prevention of A Coup d’Etat Without Sorrow”… and will the so-called “Ancients” hold the “root” password, distribute “user” restricted access towards pieces of selected fragments of knowledge?… Nausea!
Outer Space is hostile; the fragile Ark will be populated within its limit. In this context, the invisible hand of free market and its minimal and weak government (#73 Jc and #83 Michael Dunkel), or anarchy, or libertarianism are unconceivable as adequate forms of political systems. Then, democracy, scientocracy, technocracy, theocracy, oligarchy?…
I’m afraid, the Ark (like in the long-term Earth, I’m afraid of it too…), because of its brittleness, is condemned for its own survival to be ruled by a strong government, total, perhaps totalitarian, heavily concerned with ecology, hygiene, safety, prevention, a society in which each one will be tyrant of each other and the people’s life will be like the life inside a SSN or an oil platform. And no place for the rebel, unless he’ll be a remote-controlled one, like a sort of backfire or a safety valve, planed and ruled by the “psycho-history”, of course…
As far as I’m concerned, I’m not that enthusiastic to get on board, I’d prefer to await a possible progress in quantum teleportation.
But I’m fully aware that I won’t have to be too in hurry, because the future “Stargate’s Galactic Network”, if it works some day without too much entropy (I’ve the weakness to care about the integrity of all of my body’s devices!), in fact, the Arks, running at a miserable sub-luminic speed, will have to carry it trough the space for centuries before to install it on other new worlds!!!

111. 111
Justin

more likely that the arc will exist, but only after we will be able to expand a human lifespan long enough so that you will be the one to arrive at your destination, and not your descendants.

112. 112
Dan Dx

For sure, Justin, it would be a great solution.
Let’s see: Today, mean expectancy of life for human been: 65 y.
Ok, they are geographical disparities:
The winners are:
1 Andorra 83.52
2 Macau 82.27
3 Japan 82.02
4 San Marino 81.8
5 Singapore 81.8
6 Hong Kong 81.68
7 Sweden 80.63
8 Switzerland 80.62
9 Australia 80.62
10 France 80.59
11 Guernsey 80.53
12 Iceland 80.43
14 Cayman Islands 80.2
15 Italy 79.94
16 Gibraltar 79.93
17 Monaco 79.82
18 Liechtenstein 79.81
19 Spain 79.78
20 Norway 79.67
21 Israel 79.59
22 Jersey 79.51
23 Faroe Islands 79.49
24 Greece 79.38
25 Austria 79.21
26 Virgin Islands 79.2
27 Malta 79.15
28 Netherlands 79.11
29 Luxembourg 79.03
30 Montserrat 79
31 New Zealand 78.96
32 Germany 78.95
33 Belgium 78.92
34 Guam 78.76
35 Saint Pierre and Miquelon 78.76
36 United Kingdom 78.7
37 Finland 78.66
38 Man, Isle of 78.64
39 Puerto Rico 78.54
40 Bosnia and Herzegovina 78.17
41 Bermuda 78.13
42 Saint Helena 78.09
43 United States 78
44 Denmark 77.96
45 Ireland 77.9
46 Portugal 77.87
47 Albania 77.6

We are a long way out!
But women have better chances to live longer than men.
Let’s go for an Amazon’s Ark (and deep frozen sperm’s lighter to carry than men!)
Back to the charts, the world’s champions are:
1/ Andorran women 86,61 y (Andorra is a tiny principality on the border between France and Spain. Population: 71 201)
2/ Japanese women 84.6 y
3/ French women 82.8 y

We are a long way out again! And, btw, I ain’t sure that an US administration will finance any part of such a project if no american citizen is able to be part of it, due to a low expectancy of life… Imagine! The main part of the crew being japanese and french women (”Konichi wa?” - “Pas mal! Et toi, chérie, ça va?”… I would love it, I’m french! And Bill O’Reilly’s getting mad!… How yummy!)

You’re right, if we want to exclude the option “Generation Ark” the solution is to try to extend lifespan. There is a way through genetic engineering; we’ll extend cell’s DNA telomeres Then, the body’s cells will be able to divide itself much more times and the DNA will keep longer in a better condition. (Would be long to explain the function of telomeres in the duplication of human cells, so if you need, have a look at http://en.wikipedia.org/wiki/Telomere )

Ok, let’s say that we have extended the lifespan of the Ark’s crew. Now, at the arrival, we have on board an army of ardent multi-centenarian pioneers and, as far as pioneer women are concerned… post-menopausal for long and unable to give birth to a single child!
The amount of available ova in the female body is physically limited, you know…

Ok! It’s possible to increase it a bit with gonadotropin-releasing hormone!… But in the long term, it increases dramatically the risk of cancer, and during an extended lifespan, that risk will quickly reach 100%.. Need to have a strong medicine against cancer too.

Ok, don’t worry! We’ll manage to solve that issue trough a slow-down, with drugs, of the women’s ovulations frequency (at least by a factor of ten because the travel will be, let’s say, 400 years long!)… with the collateral consequence to decrease their fertility at the same rate.

Ok, ok! It’s also possible for a post-menopausal woman to carry an implanted embryo! We have already today a lot of unused frozen embryos, many more as time will pass, a good way to use them!…
With a 55 years old woman the rate of failures is already crippling, I won’t bet on the chances of a 400 years old mummy wannabe (not the egyptian one! ).

In everything, you solve a problem, many more arise! “C’est la vie!”
In spite of those issues, I keep my faith in the progress of both medicine and technology, even if, for a long while, we’ll need many magic wands,

Justin, back to you!

113. 113
Dan Dx

#2 Alan Crowe
#111 Justin
Me again, sorry. I read over your posts and mine and you know what? I doubt… A philosopher’s bad habit (and what is more, a french one. You know, we are breast-fed by Descartes, it gives bad manners!) Anyway, I doubt.
I tried last night to imagine the mug of the first genetically engineered human been, being informed that: “My son! Your mother, myself and all your uncles, the doctors, are proud to tell you that you’ll live for about 2000 years!”…

We are the sole animal on Earth who knows that some day he’ll die. We are born, we live, then we die. For ages, the expectancy of life for an adult was, let’s say, 40 years for a male, much less for a woman. The way we live, the way we behave, the way we think has been, through centuries, determined by that certainty: We don’t live forever and life is short!
The risks we take and the expected winnings are, consciously or unconsciously, hung in the balance and calculated, and the expected duration of life is among the terms of the equation. When I was younger I used to dive, risky activity. The balance between the winnings (in this case, the pleasure of discovery) and the risks (death or severe injury) is tipped in action’s favor. We are conditioned since ages to weigh up that way.

Today, the expectancy of life (at least in developed countries with a developed health care system) is growing by and by, some few months added every year. Some scientists think it’ll reach 120 years, maybe a limit. That change is slow, giving enough time to the society, habits, mentality to adapt gradually, we carry on taking risks the way our fathers and ancestors did.

Now let’s imagine! Suddenly, a new generation of genetically engineered very long livers will born, surrounded by short living parents, teachers, physicians, scientists
Consciously or unconsciously, they’ll hand on to those strange wonder kids a different message than the one we received. Instead of “Live a fulfilled life!”, those “neo-mathusalems” will grow with their parents’obsessional fear in the background of their mind: “Be careful, my son, save your precious long life!” Because their life will be long indeed, but as fragile than ours!
Will they agree to embark on the Ark’s adventure? Maybe some of them, driven by despair or boredom, wrong motivations indeed… Will they leave the safe Earth enthusiastically? I’m afraid, no. It will takes generations before this new man would internalize Nietzsche’s “Was mich nicht umbringt, macht mich stärker!” (What doesn’t kill me makes me stronger)
Zi.Ud.Sud.du, the Sumerian Noah, to whom Gods gave “a life of very long days” (his name) after the Deluge, never went to the sea again.

Our live is short indeed, but that short life is a great adventure and to take risks is a part of the adventure: Life is wider than our dreams!

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Justin

There’s noway to tell what will happen to the psyche of man when we achieve clinical immortality. Would we be forever physically 25? 35? Our age effects our emotional states and our capacity to learn. If I could be returned to my 20 year old body, would I have the focus that I have now? Would I still be able to apply the wisdom I have? Or is my wisdom solely a chemical reaction of my age?

Anyway, when you talk about a generational ship, you are ‘dooming’ the next generations to spending their whole lives on the arc. They may not wish to live there and long to return to Earth. I think the decision for a generational ship would immoral on that basis unless it was the only hope for mankind’s survival.

The only way for the trip to be morally correct for the individual would be for immortal interstellar cosmonauts to be the ones making the entire trip.

115. 115
Samwyse

Justin, the same argument could be made about any colonist. The first immigrants to the Americas “doomed” their children to living on the continent. Some colonies failed, and entire populations died. At the lost colony at Roanoke, “some ninety men, seventeen women, and eleven children” disappeared. I expect that a generation ship would not be built and launched “from scratch”, but would rather evolve from similar space colonies that would themselves have already evolved stable societies. The initial crew would have been born and raised on the ship, possibly exploring the gas giants of our own solar system, to work any bugs out of the system well before leaving for another start system.

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Chris Wren

The same ethical argument could be applied to parents who decide to give birth here on earth, “condemning” their offspring to illness, the general travails of an uncertain life, and eventual death. I would think that the decision to sign aboard an interstellar mission, even one with an uncertain guarantee of success would be an ethical decision for the colonists alone, and none of anyone else’s business.

117. 117
Gilgamesh

Sorry, I’m a bit late

Justin, the crucial question that you’re asking about the morality of the Ark project is one of the very first that I asked myself.

The philosophico-technical question is: TO WHICH CONDITIONS the fact of embarking the human species far from Earth (let’s say far enough so as it is impossible to get back) can be considered moral? Which conditions guarantee that we stay within a humanistic framework, that is, a point of view conceiving the human being, individually and collectively, like an end and not like a mean?

To this question, can one answer, right from the start and without reflecting: “to NO conditions”? It seems to me that the question deserves at least some reflexion. It can be indeed that the answer will be at the end “none”; but it can also be that there is a solution. Why not? And if it would be the case that there is a solution, let’s call this solution “the Ark”. At the beginning it may be a concept indicating simply that - and which I would reformulate as follows: the Ark indicates the whole of the necessary conditions, most easily accessible in the nearest future, allowing without moral concerns to embark a branch of humanity far from Earth, and without a project to come back.

One can then dispute such or such point amongst the solutions that I propose. But why affirm that it is anyway not possible? Man does not need the Earth, he needs a terrestrial environment. It is very different. The Ark must take the Earth as a model, but it will not be the Earth. The Ark is “all which Man needs”, needs which were developed in him by the Earth. So that this project is centered on Man, not on Planet.

118. 118
mux2000

Justin, Gilgamesh (Re:117):

When considering the morality of the ark, one must also take into account the morality of NOT building one. Assuming the ark is the only way the human species is going to spread beyond this little rock, not building one is equivalent to dooming the entire human race to a catastrophe that’s bound to happen at one point or another.

What is worse - condemning several generations to cramped and lonely living conditions, or endangering the existance of the entire race?

Another point to consider, while on the subject, is the conditions on Earth at the time of departure. A good reason to spread to other plantets, and a great motivation for colonization is if conditions on Earth become intolerable (due to climate change/pollution/war/oppressive government/whatever comes in the future), and in that case the question of morality is void, since forcibly keeping people on an inhospitable planet seems to be by far the more deplorable option.

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Steve Bowers

You might be interested in this fictional blog, which I started back in 2005 but have only recently had time to bring up to date.
http://thestarlark.blogspot.com/
it is set in the Orion’s Arm scenario, but is mostly separate from the main events of that timeline. The interstellar ship uses two speculative technologies- antimatter catalysed fusion, and hibernation by vitrification; however the vitrification process is far from perfect.

If hibernation cannot be perfected, then journeys between the stars will be long and difficult; but generation ships are not the only alternative (as I mentioned in my earlier post).

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Gilgamesh

mux,

You said:
“What is worse - condemning several generations to cramped and lonely living conditions, or endangering the existance of the entire race?”

The first alternative is maybe “preferable”, but I do not think that one can send people far from the Earth by authority: I think that it is possible for people to found an autonomous community wanting to leave, which is not at all the same thing. An authoritative project, where one would place people in ships and send them in remote regions (as for the colonization of Australia, for example) is possible only if the travel lasts for a few months. The sailors are voluntary, because they know that they are able to return! But if the travel lasts for tens of years, then it should be thought that the people who are leaving are collectively the crew of this vessel. If the motivation does not come from the crew, but that it is imposed from an external agency, I do not give a long time to the project to fail lamentably by mutiny, scuttling, and so on… It is difficult to be morally bounded (to ensure the immortality of humanity is a high goal) to a terrestrial community which despises your existence and condemns you to a containment worse than a prison. Especially that at the end of the travel there is not a viable place (like it was Australia, with a gravity of 1g, a respirable air, water, cultivable grounds, wild mammals, etc) but a planet undoubtedly inhospitable, which obliges to a confined life during whole generations.
To ensure the immortality of humanity is an immense goal, one of the most beautiful conceivable. It may constitute a very strong motivation, a moral ‘raison d’être’ to try the project voluntarily. One does not need to imagine that it must be imposed by someone. It is necessary that it is a free community, free of its destiny, and consequently the question of the following generations is very different. A community which choose its destiny rises his/her children in the love of this goal, and shares this destiny with them. That completely changes the appreciation which the future generations will have of their destiny.

Concerning the second point, I think that over geological durations (1 million years or more) the survival of humanity is in question. But that on a few thousand years, it is difficult to imagine that the Earth becomes less viable than close planets, even after 1000 Tchernobyl or Seveso, even if temperature increases by 10°C on average or that we return to Ice Age. Earth would still remain an extremely hospitable place, compared to Mars for example. If the problem is political, eg that the Earth becomes intolerable for lack of freedom, then we return to the above and moreover, it is difficult to see WHO would undertake such an adventure in such case, who would have the means for it?

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mux2000

Concerning the first point, I was assuming no coercion is involved, else the whole morality business was moot (I don’t think any form of forceful coercion is moral). Indeed, a free, voluntary community is the only way to build an ark.

Concerning the second, I guess only some rich yet persecuted minority… Hard to say, but it’s possible.

A third possibility I have just thought of will be as a vanity project for a government at war (like.the moon landing was). If the driving force isn’t ’save humanity’ idealism or basic survival instinct, it could be patriotism that’ll drive these people far far waway from home.

I think in order to reach this magnitude of patriotism though, the country sending them would have to be very very fascist, so the morality of it is debatable.

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Samwyse

I don’t see an interstellar ark being built anytime soon. First, the solar system will have to be extensively colonized; that could take anywhere from 1,000 to 10,000 years. By that time, there will be people who live their entire lives in space, in structures that will closely resemble an ark. In fact, the first ark might consist of people who have been sent to explore the Kuiper Belt; after completing their mission, they might decide to continue sailing rather than return to the inner system. Or an entire colonized asteroid, home to a persecuted minority, may decide to seek a friendlier home.

The only thing that I can see that would force an earlier exodus would be a threat to the entire solar system. A large asteroid impacting the Earth would only cause people to move underground for a while. A rogue planetoid might render Earth uninhabitable, but people would, I think, evacuate to the moon or Mars. Only a stellar catastrophe would require an ark to survive, and astronomers don’t think there are any dangers within several light-years of here.

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Gilgamesh

Thanks Steve,

Your fictional blog is an enjoyable read, and the idea of post-vitrification memory losses is well found, I find.

However, the Ark is an anti-Starlark - I hope that this does not constitute an intellectual “casus belli” between us. The two ideas are complementary, heads and tails, to illustrate what could be a space flight, at comparable propulsion system (Isp ~ 106 s).

Starting condition :
Starlark: one escapes from oppressive and unhealthy conditions which reigns on Tyr. The Earth became a prohibited territory.
Ark: prosperous terrestrial nations help give birth to a new nation formed by free citizens.

Travel condition:

Starlark: overloaded vessel, high speed (0.1 c). Quasi-prison life. Authoritative capacity exerted by Hoyle, the AI.
Ark: garden-vessel, low density (150 people/km2), slow speed (0.015 c). Open-air life. Democratic power.

The link between the two conditions is logical: in order to accept the living conditions in Starlark, it is necessary that the starting conditions are even worse. Conversely, if one starts from a happy humanity, living conditions must be even better on the Ark.

Mass:
Starlark ~ 2 x 105 tons
Ark ~ 2 x 1010 tons

The “price of happiness” requires to raise mass by 5 orders of magnitude…

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Gilgamesh

Samwyse, indeed I do not consider that the space nation would immediately give itself an interstellar destiny. At first there will be “people who live their entire lives in space, in structures that will closely resemble an ark”. Let us cross the step: this thing which closely resemble the ark, it is quite simply the ark at its stage of growth .

The Ark is made of growing vegetable strands, and starting from a few hundred meters in diameter it is already livable (in the lower part, the Coriolis acceleration generated by the rotation is impeding). The propelling surface is made of a disk, gradually increasing in size with the increase of mass of the cylinder to be propelled.

Gathering of the fusion fuel mass needed to undertake an interstellar travel is a long term effort of several generations, but during this time autonomous life in space would be already a reality. And for the arkonauts, to live on Earth’s orbit, or Jupiter’s, or Kuiper’s belt or further, that does not make any difference.

Where I am less in agreement it is when you speak about entirely colonizing as a condition to travel further. It is without any doubt a condition to be able to reach the borders of the solar system in a few months, to dispose of “spaceports”, and to be able to undertake inhabited missions of several months or years. But I do not see any requirement for the space nation to have permanent colonies on Ganymede, Triton, or Pluto. These places will be never accessible, firstly because of the weak gravity which reigns there.

In addition, I do not think that it must take “from 1,000 to 10,000 years”: I bet on an order of magnitude less, that is from 100 to 1,000 years.

125. 125
alfhiggins

This is a thought provoking article and follow up discussion…I wish I was more of a mathematician/engineer type so I could follow the math, but I can take it on faith that you know what you’re talking about.

I love the idea of a plant based structure for the ship.

I’ll have to go back and read my Kurzweil book to really have much to say about the feasibility of uploading the mind. My personal belief is that we are made up of three basic parts, body, mind, and spirit, working in unison to create human consciousness. It seems to me it will be quite some time, if ever, for us to be able to technologically transfer the spirit element into an artificial host.

What would the process of disembarking from the ship and setting up a colony once it arrives at its destination look like? Wouldn’t they need some sort of smaller vessels along, or the ability to construct them, to ferry raw materials and people around?

Aren’t there documented cases of certain yogis being buried alive for extended periods of time without food, water, and with limited air? Could these types of techniques be applied to a hibernation strategy?

Why couldn’t a single ship incorporate the several different strategies (generations, Methusalah (sp?), hibernation/cryo, embryonic, cybernetic etc.) into one amalgamated scenario?

I realize the last post was quite a while ago, but these are things I’ve been thinking about as I’ve been reading. I’ll have to see if I can find the Wiki page….

Take care and keep dreaming!

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Gilgamesh

Yes, the “hyper-transhumanist” solution is equally among the solutions which can be considered to enable humanity to leave Earth (I do not know if the term “hyper-transhumanist” exists , it is just to conceptualize the idea a totally disembodied humanity, in silicon or other support - see below the definition of transhumanism).

I have no particular prejudices against the transhumanist movement, it is an idea to be researched, but philosophically, I think that the human phenomenon is an inseparable whole:

* A biology: in biology, I put also the spirit (anima, awareness …), which is like Spinoza said “the idea of the body.” The man-organism capable of thought.
* A society: the man-organism is characterised by a hyper-sociability and only develops in interaction with others.
* A natural environment: the men in society have given birth to the so-called humanity, interacting with a biotic and abiotic environments (the starry sky for example).

With these three elements, we can reconstruct what we call humanity in its essential aspects, even if its entire memory has been obliterated in the past.

While a single thinking machine (even aware of itself and of the world) is not an humanity and can not reproduce. Even bearing in mind all that man has done in terms of knowledge and memories. And the same, in my opinion, applies to a machine without a body, without this particular interaction with a natural environment.

Of course, this is not because the spirit “in silico” is a sub-mind. But it is no humanity, is something else to explore. The ark is a “minimum Humanity”: this is the concept. (Whether technically it can be reached with the Ark of the article, it is another story…). It is a fully human entity requiring the minimum energy expenditure.

Otherwise, of course, we can add the idea that the Ark also boards an hypothetical “silicium soul” (or whatever …), or “hibernants” embryos, why not?

Returning to more “down to earth” consideration How is it possible to “land” from the Ark?

The Ark is not abandoned once arriving in the target planetary system. It remains the living environment of reference. So this is a place to live virtually forever (as a planet). Its walls are renewed permanently. The target stellar system is a largely hostile environment.

To get on this “planet”, I imagine a dozen shuttles containing some dozen of people (say 100 tons of payload) powered by fusion propulsion. These shuttles would be used initially to carry out missions in the solar system. During the last centuries of the travel, the arkonauts could of course improve or rebuild them. The ark has a significant technological capacity.

a+

127. 127
alfhiggins

Do you imagine the Ark, or perhaps several Arks, stopping at various star systems to establish colonies on whatever celestial bodies seem appropriate, staying long enough to make sure those colonies are self-sufficient and stable, refueling, repairing, and then moving on to the next viable star system? Sort of interstellar humanity spores spreading our seed through the cosmos.

Could you elaborate on the nature of the Ark’s organic construction material and the internal structure of the Ark. The three diagrams in the article are captioned in French and, unfortunately for me, I am not fluent. (By the way I do greatly appreciate the fact that you are fluent in English!) How would it be “grown” into Ark proportions? integrated with the non-organic systems? Maintained with enough water, sunlight, and nutrients through the long journey?

What are your thoughts on terraforming? Mars, for example, sounds like a decent candidate for this process in our immediate solar system. Each case would of course have different variables, but it seems we could apply basic principles we might learn about the process in attempting to terraform Mars to bodies in other star systems.

I do feel that humanity will and should focus on colonizing our immediate neighborhood to a reasonable extent (orbital stations, Moon, Mars at the very least, perhaps Mercury, Venus, asteroids, and a few of the outer system moons) before venturing to “nearby” stars, and regardless of what transhumanistic developments occur in the next few centuries. Learning to crawl before we try to run and all that.

Convincing enough people that space settlement is an inevitable part of humanities future and should be pursued wholeheartedly is another matter.

Not to mention making sure that space is a demilitarized zone of human operation. This will take an awful lot of sociopolitical cooperation at an international level to pressure the warmongering hawks enough to make peaceful coexistence a reality for space.

What do you think about the “space elevator” (you may know it by other names) idea to decrease to cost of payloads exponentially? Once they perfect the carbon nanotube technology it seems this could be a reality in the next 10 to 20 years or so.

Thanks for responding so promptly and thoroughly to my last post!

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Gilgamesh

I’m quite late, but I don’t forget you

Yes, the Ark may be conceived as the “exocytosis vesicle” of the Gaia cell. A “seminosphere” (from semen, inis: seed).

The goal is not to “save humanity”, but to spread it within the Galaxy in its own human and sustainable entirety. And I do not think that humanity is in danger in short-medium term. Even, not at all. However, at bigger timescales, at scales that formidably exceeds us, the ability to propagate our being in multiple points of the universe is perhaps the only strategy that can make humanity a cosmic time phenomenon.

And “our being”, Humanity, does not only include the biological species “Homo sapiens” (which is expected to “soon” give birth to new species), but also the biosphere which gave ti birth and the incredible evolutionary success it has accumulated in its various species.

But for this, it takes a great vessel ^ _ ^. A miniature biosphere.

One way to do it big is to repeat “ad infinitum” the same pattern, repeat the same process. Ark is a thin surface (thickness / surface: 10-7) formed by hollow identical polymer strands. In the central channel (diameter: ~ 1-2 m), filled with water which also circulates nutrients (CO2 dissolved … NPK) and light. The wall is made of vegetative fibre bundles (not giving flowers or fruits), of small diameter (some mm -> some tenth of cm) with a “hair” chlorophilian root in the central channel. The thickness of the fiber walls is the same as the diameter of the central channel.

Some properties of these fibers:
* They grow on both ends towards the light source,
* They are aligned in the direction of constraints,
* They cease to grow when the stress reaches a certain threshold and then grow in diameter,
* They wrap themselves around each other when they come into contact,
* They secrete bark as a viscous and water-resistant latex.

It is “enough” to devise such a kind of vegetal being to generate the two walls of the Ark. Initially, the Ark is just a few meters in diameter but it has already its final geometry (fiber arrangemen), and the growth can achieve sizes of the order of the kilometer.

Architecture of walls:

I cheated to represent two types of walls as one: the floor of the Ark that supports the ocean’s weight is thick (50 m or 12 ~ thick strands) and without inter-wall vacuum. The vacuum is 30 m between the sidewalls, finer (2 * 3 layers), which falls on the hub.There is very little inorganic system integrated with walls: just the gateways.

In the interior, there is an ocean of 25 m depth on which float a “continental platform” in the form of a puzzle of hexagons: the human habitat is completely decoupled from the walls.

The surface soil is about 3 m.

Total ocean habitat + ~ 8 Gt

Underneath the pattern of walls there is a diagram of the solar ring of 125 GW as a tapestry of élécroluminescent LED (light output close to 1). On the day, the ring shines on the surface of the Ark. The night it is turned off and the light power is injected into the strands, to feed the chlorophyllian fibers.

All elements of the Ark are 100% recycled (except 16 Gt of fuel, of course:)).

I’ll continue on the same later.

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Cryogen Artist

Can’t remember who the author was, but I read a novel a while ago set inside an interstellar ark going to Alpha Centauri of bout 12 miles long. It was a good read and the inhabitants were subject to the weird gravity that’s mentioned here.

Can we get to the stars in this kind of ark any sooner than tens of millennia, is my question. Can the engines of that size keep the thrust of the ark from damaging the integritry of such large scale structures? The propulsion seems to be waaayy out of what we have in this day and age, but what bout nuclear fusion? That should be coming soon with nuclear reactors coming in use in France and other countries.

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hyperlands.co.uk » Blog Archive » Interstellar arks

[…] Came across this excellent article on Slashdot last this week. Detailed anaylis of building an interstellar ark I’ve read quite a bit on the real science of building a starship. And this article is really very good, okay I don’t understand a lot of the maths, while I have a vague grasp of theories involved. […]

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Joseph Dahdah

Nice article but there are a lot of other things much worthier of such detailed consideration. There are few machines, if any, even of a simple nature, that have lasted 700 years. This would be the most complex undertaking ever considered and it seems to me that we would have to have a much better grasp of our science before seriously considering such an undertaking. I don’t think this is at the border of fantasy unless we are talking about the border between fantasy and madness. We have not yet even figured out how to sustain our way of life here on earth with, relatively speaking, infinite resources. Let’s set purely technical issues aside, even though nearly every aspect of the Ark is, in fact, technologically impossible. What social structure would sustain these people in the Ark? Have we ever developed a socio-political structure that lasted 700 years without exploitation of external human populations? 100 years? That seems an important consideration to me.

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Paco

To Joseph: I think you are misunderstanding the intention of the article; it tries to evaluate the *physical* feasibility of a certain concept. Social, political, economical and psychological considerations are treated in a very light tone, if at all, that may be the object of another article.
But going to your objections nevertheless:

- Many machines could have lasted 700 years, simply they are not useful. Think of boats, carts, mills… they are NOT built to last centuries and even if they where, they are exchanged for newer, more efficient ones simply for economical reasons. Simple machines like a compass, glasses, even clocks, can last for 700 years and have done so. And consider this is a closed environment, there is no external erosion, no wind, no rain, etc.

- We have not figured how to sustain our life on earth? what are you talking about? we have sustained life on earth for at least 100.000 years, probably more, and we where NOT trying to sustain it. Will we last 50 or 100 years more? I do not know, and neither you. It is an empty argument, global ecological considerations are totally out of scope here (IMO).

- Have we ever developed a sociopolitical structure that lasted 700 years? Yes, indeed!. Egyptian empire lasted 3.000 years. Probably that is not what you have in mind when you say “last”, but the fact is that there are LOTS of small communities of a few tens of thousands of people that have lasted near a millennium; this is from Nassim Nicholas Taleb’s “the black swan”: “For more than a millennium the eastern mediterranean seaboard called Syria Libanensis or Mount Lebanon, had been able to accommodate at least a dozen different sects, ethnicities and beliefs - it worked like magic”. Of course that came to a bloody and horrible end, but it lasted before that, and the reasons to its end where mostly external. There are many long-lasting, small communities that simply are not “interesting” enough to enter the history books. Also, most of instabilities are external: people inside want others’ resources, people outside want inside’s resources, people outside trying to get others’ resources must cross through the site… If you can maintain a reasonable availability of resources for everyone and there is no disruption from outsiders, there is no deterministic reason for a city to not last a few millennia. Many had.

By the way, you say “nearly every aspect of the Ark is, in fact, technologically impossible”. I do not agree, maybe you can elaborate a little more. This article is just about the Scientifical and technical aspects of the ark, and most if not all of them are possible, at least in theory. A few of them are not possible *now* with our current technical level, the same that 50 years ago was “impossible” to build a computer like the one I am using right now.

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Gilgamesh

Hello Joseph and Paco,

The Ark is certainly a Himalaya to go, an incredibly ambitious project. While obviously I have for this project the tenderness of a mother, my purpose is not to say arrogantly: “We will do it! Of course it is possible to do it!, Etc”. What’s would be the point? It will happen in the future, and if it will happen it will be without me.

My point is purely scientific, I hope (though emotionally I put a personal price on it), the question being: if we’d go, which would be the required resources, both human and technical?

From a technical point of view I am the first scared by the big numbers. That point by itself requires already a philosophical reflection.

Initially, the Ark is the compromise between two requirements. We need to collect both large mass or high energy. Where is the optimum? Which is the energy-mass bottleneck to go live out of Earth?

* ENERGY MANAGEMENT: we must master thoroughly and massively the thermonuclear fusion of all types of fusible isotopes in the solar system. And not just to boil hot water in boilers. Mastery of thermonuclear fusion should be up to the point of ordered ejection of 4 MeV ions through magnetic nozzles. Deuterium mostly, then Helium-3 maybe. This is the only possible source for the wild power of the Arch. Humanity is currently spending power in amounts of about 16 terawatt (10^12W) in 2010. For the Ark, it must reach 4 ExaWatts (10^18W). Just to send a human civilization of 10^4-10^5 individuals at 10 light-years from earth in less than 1000 years travel. Faster solutions require more energy, if we want to send at least as many people, and also considering that worlds at less than 10 ly does not certainly allow “bare head” colonization.

* MASS GATHERING: 20 Gt, of which 8 Gt of water. About 12 Gt of walls and building structure in space. Here, faster solutions are less massive by a factor of at least 1000. But again, they require that the target planet is inhabitable, that I think unlikely in less than 100 light-years radius, and very unlikely in less than 10 light-years.

So finally I came to the conclusion that there is not much choice, and that the solution is either an arch or again the same arch. Maybe smaller or larger, but likely measured in gigatons.

From a human point of view:

* We need a strong human civilization to undertake this.
* A new independent mini-civilization shall be founded, which is viable in long-term and independent from Earth. Then we need only to describe what such a civilization need to be at its core (small size, strong historical records, policy defined by its future targets, etc.).

I just want to detail this scope, at least roughly, of what is needed to leave the Earth.

Of course whether it will be done or not is another story. I clearly hope personally that it will be done. But I make no predictions.

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Joseph Dahdah

Gilgamesh and Paco:

The article is well done and it was a pleasure to read. It is certainly the most detailed consideration of the realities of long distance space travel, as we currently understand them, that I have seen.

My statements were primarily directed at making two basic points. The first point is that even if they are not impossible ‘in theory’, whatever that means, it is apparent that the technological requirements of even the most plausible of the cases considered in this article render long distance space travel, effectively, impossible. This will be true for quite some time and, in fact, I would expect that we must have a civilization of current or better technological prowess in place for at least a few hundred years more before such a thing were even seriously attempted. This leads into the next point; that we don’t really have a great track record as a species for making such long term plans. I dispute the claim that our high-technology society has been demonstrated to be sustainable for such a long period of time. We have many challenges; technological, socio-political, and economic that no good answers have been found for. The direst consequences of this lack of long-term planning have been held at bay with relatively cheap and abundant resources, not least importantly, energy. The assertion that global ecological concerns are not pertinent to this discussion is fallacious. It is precisely those skills of long term resource management, and due consideration of the ecological impacts of technological systems for life support and resource manufacture, that would be most relevant to a succesful expedition. The belief that the problem is somehow easier because you are dealing with a closed system which, technically speaking, you aren’t, is mistaken. If anything, the components of such an ‘ecosystem’ would be more strongly coupled together, not less.

Furthermore, the example of imperial Egypt as a model for stability seems rather beside the point. Firstly, I am sure the ancient Egyptians exploited external human populations from time to time. Most empires did, that might even be part of the definition of empire. I am looking for examples of human society that don’t do this as there will be no external human resources, or hardly any others, for a deep-space expedition to exploit. The socio-political aspect of the expedition is thus highly coupled to the technological nature of the endeavour and not to be considered in some isolated fashion.

Finally, while it is likely true that humans have existed on this planet for hundreds of thousands of years only the last hundred have been in a society which comes close to having the capability to generate, utilize, organize, and manage the resources necessary to succeed at this endeavour. That is the society that would have to be sustained on a 700 year trip. Not some pre-historic hunter-gatherer society.

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Paganel

” “the famous constant of Einstein c, the speed of light (3E8 m/s), represents an horizon speed which is impossible to exceed and which is even extraordinarily difficult to approach,” ”

I do not remember things well for GR, but I remember that SR is derived from galilean mechanics by just replacing one of its three basic relations (v=v1+v2) by what was really observed (c is constant in every referential). You turn the equations grinder and presto ! You come up with SR in a matter of minutes (well, providing you are well trained with elementary mathematics).

So the impossibility to go faster than c is dependent of that third axiom, certainly true in the (small in an universe encompassing 40 degrees of magnitude) domain of observation we have had at hand, just like Newton’s gravitation law (or its GR enhancement) was considered to describe the real wold totally until Saul Perlmutter and his colleagues showed there was a slightly greater repulsive force at work as well.

That being said, as we do not have elements to confirm or infirm that, those considerations are probably not eligible in the context of the present discussion. And of course all of us would like to know if there is hope or not there. We are in the dark.

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