Should We Build Multi-Generational Spaceships?

By Megan Ray Nichols of Schooled by Science

We’ve dreamed about exploring the cosmos for generations, and our technology has finally reached a point where that dream might be within our grasp. One thing we’re missing is propulsion technology — we don’t have warp drives or hyperdrives to carry us faster than the speed of light. Yet, anyway. One way to get us out into the universe without that kind of propulsion is to build a multi-generational ship. What are these generation ships, and should we think about creating them?

What Are Multi-Generational Ships?

As their name suggests, these ships are massive constructs designed to house multiple generations of humans, as well as survival necessities. Without faster-than-light propulsion, reaching a distant planet or solar system will take hundreds of years. The ship must be self-sustaining, providing oxygen, food, water, light and gravity throughout the journey. What sort of challenges should these intrepid interstellar humans expect to face during their trip?

Onboard Energy Expenditure

Now, we’re not talking about the energy it takes to keep the ship running — that’s a topic for another article. Instead, we’re referring to the energy you spend just surviving every day, also known as your basal metabolic rate.

Assuming you’re not dealing with the challenge of living in microgravity, generation ships will still need to create enough food to support a population of at least 500 souls for the decades or centuries it will take to reach another habitable planet. This task becomes even more difficult when you take into account physical activity and physically demanding jobs. Many of the careers on a generation ship — from farming to ship maintenance — will require additional food resources to provide enough calories to sustain the population.

Food Production2
People are inherently omnivorous — we get our nutrition from a combination of meat and plant life. In a generation ship, that means you’ll need enough space to grow food and raise livestock for an extended period. Food production gets tricky when your growing area is so limited. It’s easy to deplete the nutrients in the soil, preventing your next harvest from yielding as much or any edible food. You also need enough room to raise fish, cattle, pigs or chickens — and an adequate ventilation system to keep the methane they release from contaminating the ship’s atmosphere.

That, of course, assumes we’re going to be relying on terrestrial farming techniques and Earth-based livestock on a generation ship.

Space Farming Techniques

Hydroponics, or growing edible food in a water-based nutrient solution, and aeroponics — growing food in a misty, nutrient-rich air solution — might offer some alternatives. Astronauts on the International Space Station have been growing their food in an onboard hydroponic garden since 2002. Aeroponics is more viable for root vegetables that might not thrive underwater in a hydroponic garden.

Are We Ready?

So, should we be building generation ships to finally turn us into an interstellar species? Yes, but our technology isn’t quite there yet. We have a lot of challenges to overcome before we’ll be ready to send generations of humans on a one-way trip to the stars.

169 thoughts on “Should We Build Multi-Generational Spaceships?”

  1. I'm just waiting for some genius to develop "Cavorite".
    (See novel "The First Men in the Moon". Optimal solution there.)

    However, given our newest understandings of how gravity is not a force, but instead simply a bending of spacetime, it seems highly unlikely now. [sadface]

  2. And there is always the fact that when we look at distant exoplanets from 1,300 light years away, we are getting their 1,300 year-old image. We can't actually SEE if there's a blossoming forest or green slime smeared over the entire ball.
    We're gambling an awful lot on a trip that could end with discovering the planet was smashed by another protoplanet 500 years before arriving, and at even HALF the speed of light, the trip took 2,600 years. That would be a lot of disappointment for those arriving.
    And then to search for ANOTHER hopeful planet "only" 800 light years further in some other direction? Wow. I think our psychologies would simply evolve into becoming a spacefaring, rootless civilization of some sort, and the ship itself becoming the "home planet", that's always going "somewhere", but with no definitive, final goal.
    Because there can be none by that stage. We'll just accept it as a cultural mental survival mechanism.

  3. ??? Need "a lot of ice"?
    Ummm…. you're in SPACE, where the natural ambient temperature flutters just above ABSOLUTE ZERO!! Just keep a chamber insulated from the rest of the ship, and leave a small opening to the space outside! All the cold you need… free!
    You'd be looking, more likely, to find a way to keep things from getting TOO cold!

  4. Not "every two or three decades"… even at four-fifths the speed of light, it would be every millennia or so. Our essential awareness, our psychologies, would deplete and warp even if the bodies could live 1,500 years.
    Our minds would be exhausted, infinitely bored and probably pathologically senile if we lived over 500 years. Only about one in every 80,000 people live above the centenarian range, and of those, less than a quarter are fully rock-solid sharp and aware; but look at the millions hitting senility and derangement by the mid-sixties to eighties.

  5. I think the question is, who would want to go? Permanent exile from Earth and the rest of the human species, without even the means to have a conversation with anyone back home, unless you consider a years long wait to get a response each time ok. And you won’t even arrive at your destination in your lifetime!

    Not to mention the fairly selfish choice of giving your offspring and their offspring no choice in said exile from Earth and the rest of the species. Might be some bitter children there!

    Not saying it won’t or shouldn’t happen, but we might see some of our stranger types opting for the journey. Anti-social loners, already cut off from society?

  6. How does uninhabitable planets confirm the Fermi Paradox? The whole point is that tons of habitable planets nearby means aliens should have showed up by now.

  7. That would assume we have gestation chambers. We don’t yet have that. It is also unclear that if we had that tech that it would work on every organism we would like to bring.

  8. No, the radiation is from space or reactors onboard. Normal cells are not radioactive. There are some elements in cells with very minuscule radioactivity but there should be no issues unless millions of years transpire…even that is dubious. There may be a tiny bit of potassium 40 but even millions of years should not be an issue.
    Carbon can be gotten around as well. You can feed organisms only old carbon but I highly doubt that will be necessary as carbon 14 is very rare. Something like one part in a billion. And the half life is 5,730 years.
    No, the only serious damage that can be done would be from space radiation and radiation from reactors/atomic propulsion.
    If the DNA that is going to be used is created just before use at the destination by a machine, inserted and the original DNA removed, the damage that may have happened to the organelles should be irrelevant. As after the cell divides it makes new stuff using the info in the DNA. A few stray atoms of argon from potassium decay, or whatever, are not going to kill the cells.

  9. Phospholipid membranes are spontaneously self assembling which is obviously very simple, but you grossly underestimate the complexity of cells, especially an animal embryo. Take a look at the cytoskeleton:
    Also, a real cell membrane has many embedded components that let things in and out of the cell using complex lock and key stuff.

    There are ridiculously complex things happening all the time:

    And there is a ton of things they still don’t know.

  10. I suspect by the time we get to where we can do this, we won’t be entirely biological anymore and a lot of the questions will be moot.

    I think the main requirement would be to maintain communications with back home so that improvements in technology and science can be implemented on the trip. It would be a bummer, even for an machine-stored personality (i.e. an entirely inorganic person) to find a thriving colony already at their destination, after decades or centuries of travel time.

  11. Just use the old put-put, Laser ignition fusion. ISP won’t be crazy high. But if you go high mass ratio you could get 0.1C which should be enough to get you to the nearest star.

  12. Just have to use high mass ratio. Build the starships in orbit. lots of fuel, low payload. Laser ignition fusion should give you the ISP and thrust you need. 0.1 C will get you to Alpha Centuria in 43 years.

  13. An idea might be to send supply ships out now. To catch up with them later if a generational ship is ever created. Which is possible. Probably best to build the ship off of an asteroid while it is being mined at the time. Big ship would be easier to send off an asteroid with low amount of gravity. Gives people a purpose on an asteroid other than just mining it. If an ideal slow rotating asteroid is found. To start could send two robotic rovers, one to each of its poles to anchor in. Using material from the surface, hold material in inflatable ballast. Counter spin to eventually achieve the asteroid to tidally lock the most ideal mining spot towards the sun. Set up solar panel farm, habitats, green houses, and warehouses, then the rest of what progresses.

  14. Third such event is the breakthrough of the mediterranean into the lowlands now called the black sea.
    Given what we know about the timing, it is a default assumption that there were early civilizations in the lowland river valleys that were flooded out in what would have ben a spectacular event.

  15. And another problem and something you can’t get over with cryonics-
    nuclear decay. Because after tens of thousands of years under ice, those molecules and atoms are still going to be emitting radioactive particles. Over short time- no prob. Over long term- maybe maybe.

  16. Cells are complex but we know mostly what builds them- enzymes[mostly].
    But I am talking about 3D printing or using particle cannons to slap these suckers together. Or at least the DNA, micro RNA and associated proteins that can then build the cell[with maybe a primitive phospholipid membrane and proteins around it to make a simple gamete].
    You get the concept is what I’m aiming at.

  17. This concept will already have been developed for interplanetary cycler ships to get people from planet to planet and should not be a big leap to interstellar once we really have gotten around to using the actual resources in our local neighborhood. The martian asteroid belt will provide the seeds and once we are working on the neighborhood of neptune, saturn, jupiter, then these will get developed.

  18. I’d look to tissue culture for animal products. Livestock require feed, living space, life support in terms of O2, H2O, and CO2 capture. That being said, I’d maintain some livestock, maybe horses, cattle, chickens, and goats as cultural capital, and to keep people used to interacting with nonhuman species.
    I’d use plants themselves because they are much simpler to maintain than any conceivable alternative, and they serve to dispose of animal wastes, clear CO2, release O2, and yield food. No doubt pants for food production would be highly engineered for maximum conversion of photons, to dietary calories.
    For instance, it wouldn’t be too hard now to create a “Potmato” that would grow potato like tubers, and tomato like fruit. The potmato might even yield chiles, with a bit more work. All three plants are closely related members of the Solanace family. I can also imagine perennial ground covers that look like grasses, but who’s foliage is essentially kale, and spinach.
    A few forests, and other biomes would keep people more, or less attached to Earth, and more accepting of the natural environments they would hopefully find. I suspect there would be psychological benefits to escaping the manufactured confines of tha ship. I’d also put “houseplants” everywhere.

  19. I think you’re mixing proposals here; Nobody is suggesting high G beamed propulsion at a light year distance. You’re looking at proposals for high G acceleration over short distances, (For very tough and small probes.) and low G acceleration over long distances.

    Thousands of Gs over a light year would be seriously relativistic, and total overkill.

  20. You need a space colony on destination anyway. Of course, you can send the wordship not manned first and later a fast spaceship using hibernation or suspension to allow that the first crew will work on the destination.

    But most probably, next generations will work on space colonies too, so there is no such huge difference to live in a space colony on a interstellar travel and live in a space colony orbiting a star. The only difference is that on the star, there is a opportunity to start new projects with the resources there, but any project take time.

    Maybe from a psicological perspective could be better, for long trips, send a fleet and allow exchange of crew from time to time, just to create the possibility of “migrate to another place” for the people with they feel bad in its colony.

  21. Thing is, Mark, you’re pulling those 10% to 50% numbers out of thin air. The biggest problem of ANY nuclear power is that except for the most controlled (and contrived) situations, the daughter-product nucleons, protons, neutrons and alphas go flying off in absolutely random directions. Further, they are very likely to hit “the stuff” (not the chamber!) that’s neighboring, to lose some, most and sometimes all of their kinetic and potential energy.  It becomes heat. 

    Once converted mostly to heat, it is then subject to the Carnot Conversion cycle. And that only gets you a very small fraction of the nuclear energy as “useful” heat (but more desired, electrical) energy. 

    Then that has to become whatever-the-means devised to 

    1) create plasmas of the reaction-mass (if not the nuclear stuff)
    2) accelerate it in the desired direction (aft!)
    3) collimate it to a beam, not a swathe
    4) collect and eliminate the waste heat
    5) collect, stratify and re-use the daughter species

    THIS IS THE SAME PROBLEM even if you imagine “matter-antimatter” magic unicorn energy, if in the Real World. 

    Significantly, there isn’t enough potential binding energy to achieve more than a ship-mass of 2%, assuming P-P fusion, AND that stuff is the reaction mass.

    Just saying,
    GoatGuy ✓

  22. If I got it right Carlson is putting forward that the landscape features that have been carved show flows that couldn’t be explained by ice dam bursts and a generally slower melt. If that 3m rise happened in 3 weeks you might technically have survived but you get to restart your cities.

  23. Perhaps better put, the story of Atlantis where Plato is the only source of a date of its sinking just happens to near perfectly coincide with one of the catastrophic meltwater pulses that they are able to prove existed. Using that info you can probably place Atlantis at a certain depth and any giant cities someday uncovered at that depth might be a good candidate for the lost city.

  24. Anti-matter catalytic fusion would be cheaper. Creating large amount of anti-matter would be too energy intensive.

  25. What matters is how much percentage of the ship mass can we convert into energy. A multi-staged fusion rocket can get us from 10% to 50% of the speed of light. It would be enough to get us to the nearest star within a generation. But I don’t think we need to sent people when we can send their DNA.

  26. You are right in that progress is never really exponential. There is a slow crawl as we painfully acquired a body of knowledge. Then an explosion when this body of knowledge reaches critical mass. And then back to the slow crawl after we have solved all the easy problems. The typical “S” curve but with very long tails.

  27. How to build a generation ship:

    1) Build a space colony at one of the earth-sun Lagrange points.

    2) Populate it and seal it off for a couple of generations. (BTW: no solar panels allowed.)

    3) During those couple of generations, figure out how to propel the colony to where you want it to go and, if you’re not going to use a light sail, accumulate enough propellant for the trip. (If the delta-v budget is 2% c, the colony is 100,000 tonnes, and the propulsion system has an Isp of 50,000 seconds, that’s 20.6 gigatonnes of prop.)

    4) If the colony has remained self-sufficient, move it out to the Kuiper Belt and wait about 3 generations.

    5) If everything’s still hunky-dory, off you go.

  28. Well, that’s a point. 

    Given the whole discussion here (and years of it elsewhere), I do really think we’re about 100 to 200 years off from going interstellar. 

    NOT because I’m predicting some unicorn-horn magic technology that’ll radically change the ability to comport people and technology to the stars in radically shorter time, or to derive thrust by radically higher intensity means. Rather because we’ll first explore the local neighborhood a LOT before accumulating the fine-structure information about all those candidate planets and systems in far greater detail than at present. And, because we’ll get a lot of experience bopping around the Sol’s planetary system, using great lengths of time and rather dangerous conditions, all of which will guide the future generation-craft, whatever they really become. 

    Just saying,
    GoatGuy ✓

  29. I am not saying it is impossible to atomically build an embryo, but cells are very very complex, well beyond what we can do for now. DNA, though, we can build, and that is the part that is most easily damaged by radiation. The eggs could have some damage beyond its DNA but after divisions, all the new cells should be fine…as long as the DNA is undamaged that is used.

  30. It is plenty cold in space. Pluto is -233 degrees C. As you get further from the Sun it is just going to get cooler. Fertility clinics keep human embryos at -196 C.
    Even out at near our orbit, the James Webb telescope with a series of shades is predicted to operate at -223 C. So no powered cooling system is required, just shades. And with shades all around, you could probably get colder yet. Might even be able to get close enough for a gravity assist maneuver by another star.

    The radiation damage is the real concern to me…especially because of the long duration.

  31. Even if we don’t have a use for it, it could be like a field of dreams. It might catch the interest of the tick tacos buzzing our aircraft. Build it, and they will come.

  32. I consider this a very conservative scenario, really mundane, without crazy new physics or unforeseeable tech, we (as in humanity) can reach the stars in conventional nuclear slower than light ships, by jumping from comet to comet, from planetoid to planetoid in the deepness of space, without any big overall plan or mission, just by being human and scattering to greener or freer pastures, or at least not yet taken ones, out of the dominion of the great lords, popes and barons of the epoch.

    The endless creative longings of humanity can find equally endless spaces to settle and transform, and then generate malcontents or dispossessed to start everything again.

    And the reason this will almost assuredly happen, is that we have done this before, on this very planet. This will come, if we don’t ruin our chances and kill ourselves in the next few decades, before we can sustainably live outside of Earth.

  33. How do you “near perfectly” date something that’s not independently verifiable? I’m not saying he doesn’t have one ounce of decent scholarship, but broadly – Carlson is a crank, like Hancock.

  34. To be perfectly honest, the combined effects of aiming, diffraction and scattering are showstoppers for beamed propulsion. Proposals for beamed propulsion make hand wavy arguments about magically bringing these to near zero without any idea how. If your beam goes off center by a thousandth of a second of arc at 1LY distance, north of .1c, you get tens of thousands of G’s of rotational force and your beamed sail spins itself apart.

  35. A layer of ionized helicon type plasma around your ship absorbs most if not all incident radiation. The idea’s been explored already, there are no major technical obstacles.

  36. Necessity is the mother of invention. Spacers would have all the motivation and need for moving across space with greater ease and less mass and energy expenditure. And they would have the chance to test all kinds of crazy experiments and theories we can barely test on Earth.

    The problem I see with generational world ships, is brain’s critical mass. A world ship could have from a few hundreds to a few tens of thousands inhabitants, and that’s far less than Earth or the future Solar System.

    I imagine a person born and raised in a world ship would have very high standards of living and education compared to us, except on the obvious parameters of living space, ironically.

    But they would need each and every person’s attention for the myriads of things that aren’t fully automated and that require attention in a closed society/world.

    A similar situation can be had in the Solar System in terms of needs and opportunity, but with a lot more people to leverage and interact with.

    I believe that, if there actually is any real new physics for space travel waiting for us, it will be the first wave of space settlers in the Solar System the ones to find it.

  37. We also don’t know where to go yet?? Not going to launch then look for a planet we might survive on…right?

  38. I think we will spend a few centuries learning about living in space habitats within the solar system before someone puts an engine on one to move it to another solar system. We will probably move a few to the Kuiper belt & then the Oort cloud well before an interstellar generation ship is sent out. I’m assuming we will get fusion working within that time scale so energy for life support & manufacturing is easily available anywhere there is hydrogen.

  39. Wasn’t the objective to spread mankind across the galaxy ?. At least that would be my motivation.

  40. If the AI is smart enough, why send embryos at all?
    AI ≡ AL, as far as it goes. 
    Might as well just have a colony of AL.

  41. My bet is on embryo colonization. We send fully automated rockets, with Interstellar’s Plan B-like population bombs (thousands of frozen embryos). So it doesn’t matter if the travel takes centuries and only the freezer needs to be heavily shielded from radiation.

    Once the destination is reached, the AI locates a suitable asteroid (with water and minerals) and using robots builds an small space station recycling the rocket. Now a dozen of colons are given birth on artificial uterus and the colonization of the system can start, birthing more and more colons from the frozen embryos.

    This is far easier and cheaper than generational ships, and as we may never have fast interstellar travel or human hibernation, it may come to be the only way to reach other systems. The hardest part is to build an AI intelligent enough to locate resources and build the space station, as well as raise and educate a bunch of babies, but luckily AI is one of the fastest improving areas of our days.

  42. I’ve seen several proposals.

    1) Doppler cooling can reduce the perpendicular component of beam temperature low enough to get the kind of divergence you want to accelerate a ship over a significant fraction of a lightyear. The cooling stations would have to be spread out over a considerable distance, though. On the bright side, they can have a big enough hole in them for the starship to thread. Your original pointing stability better be good, though!

    2) Combined laser/neutral particle beam. The laser focuses the neutral particle beam via dielectric effects, the neutral particle beam focuses the laser like a very diffuse optical fiber. And the speed difference between the two supresses sausage instability as well as averaging variations in pointing, relaxing that constraint.

    3) Mass beam using “particles” large enough to have their own guidance systems. Butterfly sized smart sails, for instance. Nice thing is, they can home on a beacon on the ship, also relaxing pointing stability requirements.

  43. This will never be necessary. AI will bootstrap future colonies. DNA will be assembled from highly redundant databases, and life will be selected based upon conditions.

  44. Interesting way to look at it! Will the journey itself create advances that you couldn’t think of on Earth? Possibly, also if you pull a Cortez and burn your ability to ever go back – strong motivator to push ahead and innovate.

    But it’s gotta work with gravity. It’s like the air we breathe, gravity is absolutely necessary to survive.

  45. It sounds like a joke but look into some of what went down in Vaults in the Fallout universe. While dramatized and often incited by fucked up initial conditions setup by Vault Tec, some of the funky social scenarios are probably applicable. People lived in those vaults for 20-100 years.

  46. I don’t have the list handy so maybe this is a useless post but some academic work has already been done identifying the most valuable neighbors worth exploring. If I recall it was a decent list, something like 10 or 12 ideal locations within 40 LY. They’d either been identified as having exoplanets of interest by Kepler, or were of a stellar type and mass that would lend themselves to a decent sized habitable zone. So I don’t think destinations is too much of a conundrum.

  47. Because Noah’s Flood is a story-telling allegory, even if also nominally factual. 

    There are at least 2 “great floods” which would have put a serious shade on the closing-of-the-last-Ice-Age’s story telling peoples. The breaching of the isthmus of Gibraltar, which would have resulted in a many-year long super-flood of the Mediterranean Lake, and of course the North American glacial ice dam breaches which resulted in the Missoula flooding you refer to. 

    Thing is, while local (The Med) sea level would have risen pretty quickly, and permanently, only those peoples far, far from high ground would have had a problem. Arks are good for finding higher ground. The allegory of “two of each kind of animal” no doubt is great story-telling, but also idiotic in practice. No ptarmigans, no puffins, no Komodo dragons, no tsetse flies, no kangaroos, no rhinoceroses and so on. 2 of each useful farm animal? Sure. Generations of lıberal story telling gets the Big Story into its present allegorical magnificence. 

    The Missoula flooding however wasn’t that big a deal. I’ve read that the world ocean rose somewhere between 1 and 3 meters. Entirely survivable. Even for coastal peoples. 

    Lastly, the likelihood of a under 10,000 year ocean impact of a modestly large ( 0.3-0.7 km ) impactor is also suggestively compelling. Little remaining evidence, but the tsunami would have been AWEsome.

    Just saying,
    GoatGuy ✓

  48. A big problem with beam propulsion is you have to aim the beam well enough. Which limits the length of effective acceleration. It helps, but may not be enough, depending on where you want to go.

    It gets easier with seed ships or if we upload. Such ships can be much smaller, and can tolerate much higher g’s.

  49. Pretty much the only reactionary propulsion technology we are aware of that makes high sublight possible.

  50. Even fusion is not capable of interstellar within non-generational time frames. Fusion has been described aptly as the pickup up truck to the solar system. It will allow light vessels rapid access to the outer solar system (<1y to Pluto) and heavy lift access to places like Io, Europa, asteroids, Ceres, Mars, etc; but it doesn’t have the thrust and ISP combined to be viable for true interstellar propulsion. It just takes too much fuel to get to appreciably high fractions of c.

  51. I didn’t go into details, but there are (theoretical) ways of scaling this. This isn’t a new problem, and has been addressed in nanotech circles. (Whether it’s been addressed well enough, we’ll see when we start building this stuff.)

    The general approaches rely on exponential replication and convergent assembly.

    In the first, you start with one device (or set of devices), which is capable of building a 2nd device (or set). In some variations of this approach you start with a macroscopic device able to build a smaller version of itself. In other variations you start with a nano-sized device constructed by some other means.

    Either way, the 1st builds a 2nd, then they build 2 more, then 4 more, and so on. Until you have many trillions of them (after just a few tens of doublings).

    It has been calculated that at the nanoscale, each such device can operate a ~1 GHz (IIRC). So roughly speaking, a trillion devices, each placing, say 0.1 billion atoms per second, is 1e20 atoms/sec. ~500 sec for your example. Less than 10 min.

    Then there’s convergent assembly. This again employs exponentials, but in reverse:

  52. Sure does. (exponential relationship)

    Tsiolkovsky’s Equation is just such a stern mistress. 

    ΔV = (9.81 Isp) ln( Mend / Mstart )

    A pig that either wants a LOT of Mstart and a tiny Mend, or a LOT of Isp. And as noted, Isp increase directly correlates to Energy increase per unit ΔV

    Thing is — with beamed weapon molecular propulsion energy, you still need either to deflect the beam to extract inertial propulsive force (which means either letting it slam into your collector, or if it is charged, electrically / magnetically deflecting it tangentially), or use the implicit energy of the beam to accelerate your own reaction mass to extremely useful Isp. As in with energy that NO amount of onboard matter has/contains/can-be-converted-to.

    Or both. 
    To some degree. 

    As a vacuum-savvy electrical engineer, I think the real problem is conjuring a beam that doesn’t spread to uselessness within a few million km, and in fact will retain its tight coherence out to thousands of AU. (billions of km)

    Neutral beams? Unless condensed as particles, even they tend to diverge thru gas pressure. Ions lovely tho’ they are to USE at the spacecraft, are divergence pigs. Think stellarator, confining plasmas, wet water balloons, soap.

    Just saying,
    GoatGuy ✓

  53. The chance of serendipitous discoveries of new physical phenomena at the edge of science, is partly what makes me think we should wait a little bit and focus on going into the Solar System, with robots and people developing a self sustaining economy in space on this century.

    Of course, that’s also what we can actually do with our known science and technology.

    I have the suspicion that as more people pass longer periods of time in space for far less cost, and we can experiment a lot more with weightlessness, vacuum and the conditions of space, possibly many new phenomena now sitting at the edge of experimental falsifiability will become apparent.

    There is a long term bias in what we can experimentally measure and detect on Earth: that of Earth’s own gravity, atmospheric pressure, convection and EM interference.

    And there is a big mental inertia that comes with such environment: things that sit at the edge of verifiability on Earth will remain so as long as we don’t get out and try those things outside of Earth.

  54. The “problem” with “atomically precise manufacturing” is that you have to place the atoms, by the bazillions. Like serious bazillions. 

    A mote of dust (10 µm on a side, about the size of a materials dust particle used in present-day additive manufacturing) has a volume of about ½ (10×10⁻⁶)³ or 0.5×10⁻¹⁸ m³. In more convenient liters, that’d be 0.5×10⁻¹⁵ L. Well, let’s see at density of water, 0.5×10⁻¹⁵ kg. 0.5×10⁻¹² g. At molecular weight of maybe 27 (aluminum), that’d be 18.5×10⁻¹⁵ moles.

    Times 6.022×10²³ atoms/mole → 11 BILLION aluminum atoms. 

    I don’t care WHAT “magical thinking” atom-placement machine you’ve got, it is going to take quite a while to place 11,000,000,000 aluminum atoms to create one mote of dust. 

    Now, multiply that by macroscopic stuff … sizes … like say “a replacement processor chip”. Of the future. With 1 nm atomic minimum spacing, and perhaps 1 cc volume. Well, again,

    1 cc = 0.01³ m³ = 10⁻⁶ m³ = 10⁻³ L (duh… mL) = 3.5×10⁻³ kg → 3.5 g ÷ 40 g/mol = 0.0875 mol × 6.022×10²³ = 5.3×10²² atoms, to place. 

    53,000,000,000,000,000,000,000 atoms. 

    Say (somehow, nearly at limit of imagination), able to place 1 trillion atoms per second with atomic accuracy. 53×10²¹ ÷ 10¹² = 53 BILLION seconds. 1,700 years. For one chip. 

    Just saying,
    GoatGuy ✓

  55. Well, I suppose. 

    Just seems to me tho’ that there could be a fair number of bits in a tube (say) 1 km² in frontal area, 20 LY (190 trillion km) long. Seriously, that’s 1.9×10²⁰ m³ …

    A rather fascinating article on Wikipedia… 

    In the Solar System, interplanetary dust causes the zodiacal light. Solar System dust includes comet dust, asteroidal dust, dust from the Kuiper belt, and interstellar dust passing through the Solar System. Thousands of tons of cosmic dust are estimated to reach the Earth’s surface every year,[3] with each grain having a mass between 10⁻¹⁶ kg (0.1 pg) and 10⁻⁴ kg (100,000 µg).[3] The density of the dust cloud through which the Earth is traveling is approximately 10⁻⁶ dust grains/m³.[4]

    Well at 10⁻⁶ gr/m³ times 1.9×10²⁰ is 1.9×10¹³ grains … if the density were similar in the interstellar medium as it is here at Panet Dirt.

    Which it quite obviously is NOT.

    What’d be a good guess? ¹⁄₁₀₀₀th? Seems to be about the ratio (again, Wikipedia) of interstellar grains to local fluff as measured by several sampling satellites so far. 

    Which still leaves 10¹⁰ interstellar grains. 

    Your observation of the power-law spectrum of size-vs-number is also prescient: 100×10⁻¹⁵ g to 100×10⁻³ g on ‘average’ (that’s one hêll of an error-bar). 

    I’ll stop.
    You’re probably right.

    Just saying,
    GoatGuy ✓

  56. Like I said in another comment, beam propulsion lets you escape the rocket equation, by eliminating the need to carry along both reaction mass and power generation.

    The chief difficulty is that, barring equipment at the other end, it isn’t very good for slowing down again. So early missions will probably be a mix of beam propulsion launch and onboard propulsion at the other end. Given the exponential relationship between delta V and fuel fraction, that helps a lot.

  57. A gigantic shield in front of you. There was a novel by Arthur C Clarke called Songs of a Distant Earth that did just that. Used ice and it could just be replenished at various stops. That way then the front gets hit by all of those tiny molecules, it just hits the shield.

  58. Never liked the idea of Seed ships because you have to keep the embryos on ice and that requires a lot of power.
    I prefer my own idea of a builder ship. Bring the elemental and atomic structures[Carbon, Oxygyn, Phosphorous, Nitrogen, Calcium, etc] to build an organism[however primitive or complex you want] from the ground up. So we would be able to build gametes, with DNA, proteins and cell structure from the ground up and then let the embryos develop.
    Then have robot tenders take care of raising them and their food sources.

  59. It isn’t a problem for a lot of reasons. Not least of which is by that point we will have simulated realities to escape into.

  60. Randall Carlson is becoming relatively well known for offering some reasonable theories that explain the source of the biblical flooding. I think they’ve all but proven a 500-1000 ft. river flowing across 5 states of the pacific northwest and the theory that has been gaining traction is a meteor hitting the ice sheets. Apparently Plato also near perfectly dated Atlantis to one of the big meltwater pulses. Most of civilization would probably have been on the coasts and wiped out but since it wasn’t truly global flooding it covers your woodworms and termites. I think they also found massive monoliths at the bottom of the Mediterranean that guarantee severely astrologically savvy civilizations are at least 9k years old. He has some good interviews on the Joe Rogan podcast. And as usual I’m a little confused. How are animals besides humans seemingly immune to the re-population requirement of lots of genetic diversity.

  61. (cont.)

    Nowadays there’s so many things going on, it’s hard to follow. Granted, much of it isn’t as big and flashy as the invention of powered flight or discovery of penicillin, but it’s there, behind the scenes.

    Anything related to electronics (and to a lesser degree, software) has been advancing exponentially for decades. Some of it has slowed down in recent years, but only because we’re approaching the end of the silicon S curve. That’s until we cross to the next ‘tronics S curve, be that spintronics, or optronics, or whatever. Meanwhile, robotics and AI seem to be speeding up the last few years.

    Other areas like medicine are more silent. But there’s been major progress there too. Of course, some of the big tech has slowed down, since it matured and reached the end of its various S curves. But I don’t think progress in total has slowed down. It just became more mundane. And we became more jaded.

    EDIT: Forgot to mention that some (many?) fields are being digitized now, turned into big-data problems and so on, which should enable them to speed up significantly in coming years.

  62. A generation ship is basically a space big colony like a O’Neill Cylinder plus a big interstellar (slow) ship.

    Before that, we must develop that propulsion (fusion, laser sails, etc. ) but even more, that space colonies.

    To master space colonies, we need to dominate solar system resources.
    To control solar system resources, we need to develop massive IRSU and very advanced robot automation and space manufacture technologies…

    So… a lot before reach that point.
    I guess start with some colonies in space, Moon, Mars and some orbital or L4/L5 outposts are a good start.
    Let’s do that.

  63. Technology tends to go in S curves. The start of each S can resemble an exponential, or at least a power function. The end of each S is more like a logarithm, or a power function with power < 1.

    Progress as a whole is a sum of many S curves, each at a different stage. But by standing on the shoulders of giants, each completed S curve enables multiple new ones. So overall, progress should be accelerating.

    I’d argue that biological evolution follows a similar pattern. In fact, technological progress can be likened to evolution of ideas.

    – ~9 billion years for the Earth to form and the first life to appear.
    – ~3 billion years for eukeryotes to evolve.
    – ~1 billion years from the first eukaryotes to modern animal phyla (Cambrian explosion).
    – ~0.5 a billion years from there to the first primates.
    – Less than 100 million years to the first hominids.
    – ~5 million years of hominid history.
    – ~3 million years of stone tools (predating the genus Homo).
    – A few hundred thousand years of “modern” human species.
    – ~10000 years of agriculture and settlement (since the Neolithic revolution), and early metalworking.
    – ~5000 years of writing and bronzeworking.
    – ~3000 years of ironworking.
    – Less than 500 years since the renaissance. A bit more since the printing press.
    – Less than 300 years since the industrial revolution (steam power, early modern steel).
    – Less than 200 years since the first polymers.
    Just over 100 years for most modern technology.

    (cont. in reply)

  64. If it’s a generation ship it isn’t going to be pulling high Gs anyway. You can actually physically push on a quark nugget, if they exist. (Unless it was a strangelet, under some hypothetical physics, where pushing on it would just get you turned into more strange matter.)

    Micro black holes would be a pain to manipulate, only gravity would really be available. (Trying to charge it just causes the Hawking radiation to be biased towards that charge, discharging it again.)

    But they’re both hypothetical thus far. Might find some of those quark nuggets once we start mining asteroids.

  65. In terms of pot holes, we have a pretty good idea of the average density of material in space, based on gravitational influences, and the fact that we can see distant stars. And there’s certainly a power law at work, most of that material consists of isolated atoms and molecules, much less of it as dust, still less as grains of sand, and so forth.

    So we can calculate rough estimates of the probability of a ship of a given sectional area encountering objects in different size ranges for a given length of trip.

    I think the numbers, from the last time I looked, don’t actually look that bad. Your odds of hitting anything bigger than a grain of sand are pretty slim.

    Mind, you might win the lottery, and go down in the history book as the first interstellar ship to be converted into a ball of plasma by hitting something large. But I think you can design your defenses around sand grains, and just accept that you might get your ticket punched if the odds go seriously against you.

  66. The theory behind the process, to put it simply (perhaps too simply).

    I don’t think innovation is a requirement for survival, for the most part. As long as they can duplicate the process, they can study it and experiment with it, and eventually figure out the theory. It’ll take longer, but it won’t kill them.

    Not being able to reproduce the process will kill them much faster. But sure, theory helps.

    (P.S. Good documentation includes not just the “how?”, but also the “why?”, which is a big chunk of the theory. That’s just as true for proprietary processes. But I agree that many organizations neglect good documentation.)

  67. Micro black hole or quark nugget… (Goat smiles)  
    I think their ‘problem’ is that they don’t play along with being moved.
    Using inertial forces or electric.

    But ⊕1 just the same!
    Especially for sending the VNM beforehand to target.

  68. “But even with proprietary, it’d still be documented and formalized into code somewhere.”

    You’d like to think that. I wouldn’t count on it, when it comes to something like a design process, as opposed to manufacturing process.

    Sure, we have documented how we make product X, even though we don’t tell anybody else how we’re doing it. Have we documented how we figured out how we make product X?

    Not so much. That’s the sort of knowledge I’m talking about. We don’t want the colonists to be stuck just exactly duplicating things they don’t really understand, we want them to know how to innovate.

  69. Yep I can imagine it, because I did months at sea like that. One ‘trick’ is that there are no passengers, only crew. And every member of the crew has productive work to do every day. So add to the list of problems – population management including: Identifying productive, satisfying work for everyone on board. Population control. Human competitiveness, with a base crew of 500, you will develop factions as well as individuals who love and loathe each other.

  70. Or, once the tech is there, grow just the edible parts through tissue culture (we’re close, but not quite there yet). Or synthesize the proteins etc and assemble them into edible forms (further away, difficult to get the looks, taste, and texture right).

  71. There is the Later-Faster problem. Decades or centuries before world ships launch, we will have mastered animated suspension, raising from frozen embryos or data, etc. So, given the same amount of energy for propulsion (I prefer beamed) then these smaller craft will arrive at destination far sooner than the worldship.

  72. The larger industries tend towards standardization as they mature. It’d nice to have a set of open-source automation standards for at least the most common/important processes.

    But even with proprietary, it’d still be documented and formalized into code somewhere. Just not as accessible. It’s not a stretch for a space colony or generation ship to require all process providers to include and license their full source code, documentation, etc.

    Of course, they’d also be required to optimize the process for the needs and abilities of the colony. Just like today there are extra requirements for space hardware.

  73. For fast trips, beam propulsion with as small a ship as feasible is the way to go. Ideally, first you push out a Von Neumann machine, that builds a beamer at the far end, then when you hear back from it, you start launching your manned ships, that use external power at both ends, and so aren’t limited by the rocket equation.

    For generation ships, you colonize a comet, use the hydrogen for fuel and propellant mass, while mining the heavier elements. Eventually you convert the comet into the fueled ship you use to stop at the other end.

    But that ideally requires us to master P-P fusion, and that’s going to be really challenging. Be nice if we found one of those hypothetical “quark nuggets”, as they could enable efficient mass-energy conversion without regard to the elemental composition of the matter fed them. Or a micro black hole in the right mass range to use as a power source.

  74. As with all space expansion ideas, the question remains what’s the benefit for those who stay behind? Those would be the people who sacrifice the most for such an endeavour.

    It’s a silly idea too think that we need to colonise distant planets. We could colonise our own deserts, the poles, the ocean surface and the subsea first. All of those are almost guaranteed to be more suitable for sustaining human life than some distant planet, even if the latter is in between Mars and Earth in regard to habitability.
    We could easily reach a hundred billion people population on earth before even only Mars becomes a better colonization option.

    I suppose we should send at most long durability drones with AI and self-maintenance robots to survey potentially habitable planets and to drop atmosphere-producing algae and bacteria onto them. That could be a very long term investment.

  75. Yeah, this used to be a sci-fi trope in the 70s. The multi-generational ship arrives at its destination, after centuries of civil wars and religious cults and schisms and jokes that the ancestors once lived on a round planet called ‘Dirt’. Once there, they are greeted by an advanced society that make can the trip to Earth and back in a couple of hours.

  76. The problem with any type of rocket, is that the more fuel-efficient it is (higher Isp), the less energy-efficient it is (more energy spent accelerating the propellant, less of the spent energy becomes kinetic energy of the ship). So either we need lots of energy, or prohibitively lots of fuel.

    Furthermore, for any constant power, the higher the Isp, the lower the thrust, and therefore lower acceleration. And the higher the fuel mass, again the lower the acceleration. If we want to get anywhere reasonably fast with a rocket, we need high Isp and high thrust, and that means lots of power.

    To get around that, we’ll either need some new means of momentum exchange that doesn’t require throwing stuff out the back, or something similar to a warp drive (even if sub-luminal). So far we’re limited by the physics we know, and there may not be any suitable physics yet-to-be-discovered. Even if there is, we’d still need at least as much energy as necessary for the kinetic energy of the ship, or as much as needed to form the warp bubble, plus inefficiencies. Either of these can still be very high.

  77. Agreed on that. As an engineer I know quite a bit of the design process for my little corner of industry is poorly documented, or even kept proprietary. Poorly documented we can do something about. Proprietary is a bit harder.

    But an automated, self-sufficient industry on a small scale isn’t likely to use the same processes a huge industrial ecology does, because it’s too small for the payoff to be there for optimizing this or that. The tendency would be to use non-optimal but more general processes.

  78. I think atomically-precise-manufacturing is the criticality point (or at least a requirement – there are other critical bits of knowledge besides it). Once you have that, all of those hundreds (thousands?) of complex manufacturing processes reduce to a fixed set of atom placement operations. If you want to make something else – almost anything else – it’s the same operations, just in a different order. There are (so far theoretical) ways to scale this to make macroscopic products.

    Some stuff may still need specialization. For example, making long sequential molecules like proteins and DNA is a little different from making silicon crystals. Squishy molecules in general are more difficult to handle. But it’s still a finite set of operations for limitless different products. If we’re clever, we can make almost everything from just 4 very common elements: CHON. Throw in a bit of others for doping and nutrition.

    Recycling also becomes relatively easy – it’s just manufacturing in reverse.

  79. It would be really depressing if you set off for a two hundred year journey at .1 times the Speed of Light and when you got there you found out that humans were already there because technology evolved and ships traveled at .7 times the Speed of Light.

  80. So we need a WikiSkills? I think the more stuff we automate, the more this problem will begin to solve itself. Automation requires formalized processes. I expect the most important processes should tend to have a lot of money riding on them, so they’re likely to get the most attention during our journey towards automation.

  81. Storing millions of human genomes on a flash drive would take some work. Google says it’s ~3 billion base pairs. ~6 billion bits, ~0.75 GB. 1.5-3 GB with redundancy for error correction. Naively, a typical flash drive can store a few tens to a few hundreds of those, not millions.

    It can be compressed a lot by storing the common parts only once (+redundancy). But even if we assume the unique bits are only ~0.1% of the full genome, we’re up to a few hundred K or so.

    The next step could be using an index of gene variations. If we allow up to 16 variations per gene, each variation can be selected with 4 bits. Then a single 20K-genes genome is 10 KB.

    The average human gene size is 10-15K base pairs, which take 20-30 Kbits. If we only need to encode 0.1-1% of that, that’s up to ~300 bits per gene variation. Call that 40 bytes. So we’d have 3 GB for the full reference DNA data (4-way redundancy, since this is the most important data), 20000 * 16 * 40 = 12.8 MB for the gene variations index, and the rest for the genomes at 10 KB each.

    So yea, millions to tens of millions of genomes, even if the gene variations index is 100 times larger. One could probably compress some more over the above. Or one can generate random combinations on the fly, as you suggested. Then only the ~3-4 GB of reference data (including gene variations) is needed.

    Also, I’m optimistic re artificial wombs and eggs production by cell reprogramming. The basic principles have already been demonstrated.

  82. I’d be terrified to get into a box with thousands of people without some very clear definitions of government and law. I imagine some will launch with socialist style pacts and others with strong individual rights, like you own part of the ship. That could fall under ethics. There will surely be some study worthy events. What happens when the politics shift on an unlimited length journey? Are you allowed to get off and use nanobots to spawn your own generational ship out of the nearest asteroid cluster or are you considered mission critical?

  83. We’ve gotten good at turning regular cells into eggs, too. So if you can replace a cellular genome from scratch and reprogram a somatic cell into an egg, you could start with simpler, non-human cellular stock. The gestational chamber is still the kicker.

    But even then, why a human womb? Why not bring some (hibernating) rodents, and reprogram their cells so their progeny will be bigger rodents, then, say, dogs, then monkeys, then chimps… and… you get the point. Shoot, you could start without the animals entirely and reprogram through multiple stages (recapitulating something like evolution) until you’ve turned a yeast into something that has a womb.

  84. Build o’neil Cylinders out of moon rock and shape a comentary orbit out to the belt or Jupiter Trojans or the ort cloud then repeat – test the systems with longer trips but with the safety net of still having access to the earth think flying cities/factories/colony seeds – the ground is for the stay at homes – become homo galacticus

  85. I’ve always considered multi generation spaceships as an awful idea.
    First, it’s awful for the people embarking, because they will live the rest of their lives on a spaceship.
    Second, it’s awful because you’re forcing your decision on future generations.
    Third, it’s awful because you can get a better result if you solve cryogenic preservation.
    Fourth, by the time the generation ship gets to it’s destination, technological advances on Earth might allow for better solutions and faster spaceships, making the whole ordeal useless.

  86. That’s pretty much the scenario I envision: First we start colonizing the Solar system. We get practice at making colonies independent.

    Then some people already living in space colonize an outbound comet, and for one or another reason decide they don’t want to come back. So they give it a boost to go hyperbolic, and you’ve got your generation ship.

    But it isn’t aimed at some nearby star, because they know quite well that star will be colonized before they ever get there. It’s just aimed away from Earth. Maybe they have one of those rogue planets in mind, or a brown dwarf with orbiting bodies. Or just hope to find another free comet out there.

    They will be looking beyond their own comet, though, because in the long run, the very long run, away from stars, comets are not endlessly habitable. You eventually run out of fuel, because you can’t live off the output of a nearby fusion reactor that’s going to be running for the next several billion years. A comet might be habitable for 10s or 100s of thousands of years, but not for the time periods a planet can be.

    And, why do they did they leave? Probably social or genetic experimentation; They want to try out a new (or old!) way of life, and know that if they stay people might interfere with what they’re doing. So they get out of sight in the hope of becoming out of mind.

  87. By the time the 3rd gen is out there plying the waves of space, Earth will have figured out how to travel really, really fast or get from one place to another instantly, and invented all sorts of cool things. The look on the faces of the “Santa Maria” ark when Earthings buzz by in their spiffy interstellar transport wormhole vehicle to offer the primitive tribe some modern offerings. Cure for cancer, free fusion energy, unlimited food production, etc and a trip back to Earth if they wanted it, or, an upgrade to their decrepit asteroid so they can continue on their journey in deluxe comfort and unlimited speed.

    The analogy would be – would you prefer being locked up in 1919 (pre-penicillin) with friends and family with a candlestick phone for outside contact, to one day get a knock on your door 100 years later, or would you rather be part of human advancement? Wars and other horribleness notwithstanding.

  88. What’d be the point? If we can build self sustaining systems like that, why accelerate them to 0.1c when we can just leave them where they are and use solar energy instead of generating their own? Dyson swarm it first before spreading.

  89. Might be side effect of the trade war stuff with the US, so US exporters are not yet getting deep into it? Apparently spanish and other pork markets are facing higher local prices while more is being exported to china, as the swine flu culling means the chinese domestic herd size will be seriously damaged for a few years allegedly.

  90. Whole genomes have already been synthesized from scratch. They were simple viruses and bacteria, but it’s been done.

  91. Said nuclear electrostatic cells have been tried. The issue as I understand it (from my very poor background in the area) is that converting super high voltage, super low current electric charge to a more useful high current low voltage (say 5 MV to 25 V) is not easy with DC.

    If it was AC it would be trivial.

  92. When I envisage someone escaping the solar system via a generation ship, that would probably start with a community already living in self contained space habitats. They take said habitat, accelerate it up, and keep living as they always did, but now without communication to the rest of humanity.

    One further assumes that this would be an outer solar system habitat. The inner system places wouldn’t have bothered being solar-independent (unless the brave new energy source proves so cheap you wouldn’t bother with solar power, even in space) and the outer system places are probably where the most independent and likely-to-do-something-radical-as-a-solution-to-their-problem people live anyway.

    Lastly, in the event that the reason for running is takeover of the Sol system by the resurgent Quetzalcoatl cult or whatever, then those least favouring the return of human sacrifice have probably had reasons to try to get far away from the crazy dirtsiders for a number of years already. That sort of thing doesn’t happen overnight.

    If the disaster is a rogue black hole heading for the sun, then all bets are off.

  93. Communications – seems like a chain of comm relay stations, one launching every month perhaps, could keep the ship in touch? Each needs its own multi-century power supply, of course…

  94. A thought on ‘pot-holes’ – if a chunk of whatever were to be intercepted with a disc of roughly equal mass and diameter, well out in front of the ship, at fractional C velocities I’d think you’d be left mostly with plasma.

    Add a powerful magnetic field to divert the plasma to the sides. And maybe divert the electrons to a central mast – allowing recovery of some fraction of the energy – though possibly in such a big jolt that the only practical use MIGHT be to divert it into accelerating the plasma as rocket exhaust, or maybe to boost the magnetic field during that critical diversion period?

    And if possible, collect some of that plasma, because a lot of interceptors will likely be required for a multi-century journey, and mass will be at a premium.

  95. I think we should start with space stations for 10k+ population each. That’ll give us expierence on maintaning such ecosystems without risks involved with long-range journey.

  96. I concur, we have become a profoundly conservative and fretful society, where everything changes but nothing does it substantively, lacking the chutzpah to do some crazy endeavour like this just because.

    But in my view, the hypothetical society that does have the gall to do it, could indeed be one that already exists and doesn’t give a hoot about the ethics (the rogue states mentioned), but also one pending to be born, where such things as living in space are as natural as breathing.

    People in the far future that have been born in space, grew in self sustained, self replicating artificial habitats, free from Earth’s nefarious cultural influence, earning a living from rocks in the cold deepness of space, will have very little fealty to the cherished ideals of a decrepit, decadent society, clinging to obsolete morals as proof of their superiority.

    They will simply turn around, take their stuff and leave, and this will result in an hegira of humans taking them into farther and farther frigid worlds, across deeper and deeper regions of space.

  97. The USSR heavily pursued single cell protein (SCP) sources as a way of dealing with nutrient needs via industrial sidestreams (seems they did a lot of manufacturing as colocated industries to oil refineries), so integration into a recycling/ISRU rig for a generation ship is de rigor. The costs aren’t terrible all-in apparently on a kg basis. For russia in particular, with the loss of the breadbasket that is Ukraine, they may need to reconsider reactivating some of those manufacturing plants.

    Considering the current swine flu devastating pork production in china causing a global pork price spike (and requiring activation of the chinese strategic pork reserve), one wonders if there might be a crash program for SCP there, or if the chicken industry is about to get heavily upgraded.

  98. Energy-wise, it seems like WELL contained antimatter-matter annihilation, with magnetically directed emission-beam capture.

  99. I’ve tried to wrap it up in a way-larger way, herewith. Take a look. It ought to be interesting… GoatGuy

  100. Actually … I do (think a either a multi-generational at least, or a controlled hibernation ship) is needed.  

    Your terminal point is actually what drives that opinion (as I am hoping it will re-shape yours).  

    I quote “it would be better to colonize the galaxy in small steps”. 

    Think what that means, if it turns out that we really are limited by the Carnot thermal efficiency equation, along with electrostatic sub-nuclear radiation dynamics.  

    IN THE END, (at least by my reckoning) I doubt that we are going to derive energy-of-the-nucleus-to-directable (electrical) energy much better than the so-called “nuclear electrostatic cell”.  

    This is where an alpha (or beta) emitter is sitting at a tip-of-a-needle, radiating away mostly without molecular adsorption, in all directions. 

    The alphas, or betas are charged, and have a lot of kinetic (motion) energy.  If they are drifting into a strong electric field (i.e. against their charge), they give up a lot of momentum to overcome the electric field. 

    When they intercept the “plate” however, they deliver their charge at HUGE efficiency. Basically the highest efficiency nuclear reactions possible. 

    Thing is, then the power generated needs to accelerate REACTION MASS to high velocity, to push the shipcraft foward.  

    And at 5.7 megawatt-hours per kilogram of RE mass … wow. That’s a lot of nuclear energy.  

    Just saying,
    GoatGuy ✓

  101. I rather think that it is a 50th century problem. 

    We tend to believe our own shît too much . I am getting far older than I like, but the net take-away is that we really aren’t progressing forward at the “exponentially increasing rate” that has become common parlance.  

    We’re perhaps (questionably) linear. 

    More likely we’re actually logarithmic fundamentally, but with “high polynomial” multipliers on the logarithm. What this means is that to ordinary sub-math-genius mortals, it LOOKS exponential, but it is, in fact, not. 

    And that — as it turns out — describes most of macroeconomics as well as much of history of Mankind.

    Just saying,
    GoatGuy ✓

  102. ⊕1… Yay … someone (an old friend, if I can be so presumptuous), said “I think our society won’t find a reason to raise a generation ship that’d go anywhere”.  

    I definitely agree. 
    We’re held hostage by our duplicity, mendacity and ignominiousness. 

    The motivation of “oh fûque! The space-aliens (AKA Russians / Commies / Pinkos / Cranky Eritreans) are going to eat our years-of-lunch! Arrggghhh!  Let’s blow this rock!

    That motivation is probably the ONLY motivation that’ get the supremely duplicitous, mendacious and tirelessly banal toadies off their lily-pads.  

    Think though, Doc (prosaically).  

    The “problem of destining thousands of souls to a certain end” can be auctioned off. Given the rather remarkable proclivity of tiny percentages of people to fine common cause in rather stretch-remarkable performance Art, well … it wouldn’t take very long to fill the Cosmic Martyrs waybill.  

    Anyway, in an overused trope…
    Just saying,
    GoatGuy ✓

  103. I don’t think our society would make a generation ship to go anywhere.

    There are some important words in that sentence.

    I don’t think OUR society… we have, even the most extreme political power centers within our society, we have certain values and approaches in common. And none of these would choose to condemn generations unborn to a life in prison so that their distant descendants can risk their lives settling a distant star. But some other society? North Korea? The Revised united Caliphate of Southern Europe? I won’t rule it out.

    … go anywhere. No, as stated above we wouldn’t do it to go somewhere. But to GET AWAY FROM is a different matter. Escape. That motivation works. Escape from a solar system destroying disaster (fill in the blank). Escape from a solar system conquering enemy? That story works.

  104. ⊕1 … at least do me the favor of reading the 10-odd little 1500 character-limited sub-comments I added to my own 1st level comment. If you would. I appreciate your opinions, and for whatever reason, I’ve outdone myself on this topic today.

  105. That would be the “hell” that was normal life before modern times.
    Most people spent their entire lives in the villiage/island/valley they were born in, with a population of a couple of hundred at best.

    Though admittedly they didn’t live for centuries, folk tales notwithstanding.

    Not saying that I would enjoy it, but clearly it is within human capability given that billions of people managed it over the millenia.

  106. “rogue planets” between are the very definition of useless, for those aboard the generation ship. Why?

    Because we are NOT in a Star Trek / Star Wars universe of physics. You can NOT “go sub-warp, Scottie”, or sidle up to a planet like in the movies, in a couple of minutes. It takes billions of gigawatt hours of power to accelerate the ship up to speed, and it takes equally more billions of gigawatt-hours to drop down to hook up with the rogue planet, to see what all it has going for it.  

    Then the SAME billions of gigawatt-hours to get back up to speed.  

    This also goes for “scout ships” or any kind of conceptually shuttle-craft thing to intercept the rogue.

    Anyway… remember, PHYSICS is a harsh mistress. Inflexible, righteous, mathematically predictable to 7+ decimal places.  

    Just saying,
    GoatGuy ✓

  107. Generation starship is applying 20th century solution to a 22nd problem. Future starships will be size of poppy seeds. They will ride beams of light. When they reach their destination they will find an asteroid where they will plant their roots and grow into mighty trees that will bear human fruits.

  108. The rule is if waiting for better technology will get you there early then wait. It would take 400+ years to reach Alpha Centuria at 1% the speed of light so it would be better to wait. At 10% of the speed of light it would take is 40 years and it would make sense to go.

    I don’t think a multi-generational starship is needed. I think it would be better to colonized the galaxy in small steps.

  109. № 1 – Energy

    COLLOSSAL amounts of energy are required to accelerate the “reaction mass” out the back of the ship to propell it forward at a meaningfully high velocity to make it between the closer star systems (say out to 25 light years) within 1,000 trip years. Even ¹⁄₄₀ c (25 LY in 1,000 Y) is mind-bogglingly expensive, energy wise.  

    IF (for instance) one budgets 75% of the starting mass as outgoing reaction mass, and 75% of the remaining mass as deceleration mass (leaving 6% of the whole thing as the payload), accelerating that 75% high enough that the 25% remainder has a ΔV of 7,500,000 m/s requires a reaction-mass exhaust speed of 5,400,000 m/s. 14.6 TJ/kg. 4 MILLION kilowatt-hours of acceleration per kilogram of exhaust.  

    What’s going to provide that?
    Its the MAIN challenge.
    All else combined is a distant second.

  110. № 2 – Ecosystem

    Technologically ginning up an ecosystem that can be maintained essentially indefinitely, for a thousand years, generating oxygen, food, recycling CO₂, metabolic waste products is just the tip of a larger iceberg. (See № 3). While it sounds prosaic to imagine huge 3-dimensional hydroponic farms, enormously powerful fusion powered ‘light bulbs’, an so forth, in the end, Ecosystem itself is nearly beyond imagining in complexity. 

    № 3 – Atom recycling

    Then there is the recycling of degraded-to-useless machines, motors, clothing, electronics, materials, stockpiles. The “closed system” aspect is what causes MY mind to reel.  

    Not only would the generation ship have to be able to continuously recycle and remanufcature all the THINGs, it’d also have to recycle nearly if not all the recycling equipment, the chips, the circuits, the esquisite tiny-stuff that we otherwise take as given. The manufacturing capacity requirements are astounding… foundries for metals, chemical plants to purify things, to separate different elemental species.  

    Just consider a microwave oven, as a really simple recycling case.

  111. It breaks (mostly) because the magnetron’s vacuum dies or the filament breaks. Or the volt-doubling capacitor blows. Or the insulation on the transformer blows. Each of these things is partially avoidable (as for a ”generation ship”) by adopting a revolutionary power system aboard ship. A low-volt supply to power hundred-year filaments. A high volt supply as well. A ‘logic supply’, mostly uniersal to all shipboard electronics.  

    Still, more engineering needed. The silly present-day film-type front panels definitely have finite lifetimes. I suppose they can be made anew as they break. Film, conductors, print-on-demand manufacturing. Still, the plastics used will gradually oxidize, become brittle, break. Latches wear, metal-to-metal contacts wear, spalling metal bits. Which get everywhere. Magnetics? Sure! But magnets demagnetize over centuries. Its there way.  

    Now imagine a 3D printing machine… what’s going to break.

  112. № 4 – Radiation abatement

    The generation ship will be bathed in radiation, and more from the ‘front’ than the rear in general. It is HARD radiation, capable of making it thru meters of material. The radiation-damage tracks from all those quintillions-of-passages-per-year … are hugely damaging to Kingdom Animalia, and rather so to the plants and microbes. But they’re also accumulatively damaging to things as mundane as glass (turns amethust, then black), to plastics (yellow, browning, crumbling), to crystals, to semiconductors, to polymers, fabrics, almost everything except metals and mineral oxides.  

    Being deep inside helps — a lot — yet still has to handle the century-scale effects. Everything frangible that franges (breaks) needs replacing. And how? Giant magnetic fields are conjured, but to maintain them requires maintaining their coils, which too degrade. Making one’s generation craft from a big metallic chondrite helps… and provides materials. But much of the material ends up being reaction mass.  

    Radiation is a problem.

  113. № 5 – Technological criticality

    Since everything needs to be manufactured in situ, there needs to be enough manufacturing capacity and diversity to make ANY CONCEIVABLE replacement part, subsystem, or whole machine, entire. This means that chip-making equipment needs to refine silicon from ore, purify it from clinker, crystallize it into slabs, saw them, polish them, make masks for the “printing machines” that’ll maybe make more chips. And the designs for the masks need also to be made again. And again. As things wear out.  

    The chips need to be tested by equipment which might not last the trip. Which WON’T last the trip. Which need to be made again, or endlessly fixed. From parts from dwindling original supplies, which themselves must be made up by re-manufacture.  

    See the complexity? You need a LOT of stuff just to keep ALL the stuff working.  

    It might be fruitful to imagine, “what wold the smallest possible autonomous civilization be” that could maintain a year 2050 technologically dependent mix of machines, devices, informatics and civic structures?

  114. № 6 – Exogenous Unknown Development

    Then we have the under-a-million souls on the generation ship, chugging along, with the hobby of advancing technology and science, one might suppose … compared to the tens of billions left back on Terra. Who will be inventing at a million times the rate. Stuff. Stuff that could be critical. Could have been. Can’t be: insufficient critical resources. I don’t imagine a lot of that, but it’d definitely suck. 

    № 7 – Interstellar pot-holes

    Oh, then God tosses grenades in the path, don’t you know? Chunks of interstellar stuff that hasn’t been wafted out of the path by the last billion years-worth of supernovæ supersonic gas. Chunks. Clinkers. Impactors. Death.  

    A ‘thing’ intercepted at 7.5 million meters per second will have a LOT of damaging energy. A lot. And a multi-generation ship ain’t going to be able to nimbly shift-out-of-the-way very quickly. This’ll definitely require a whole batallion of forward reaching craft with lasers, sensors, optics, metrology. Have to detect the baddies, and vaporize them at a minimumm. Or hit them with femtosecond megapulses which shift their trajectory off-axis. Out of the way. But they HAVE to go.  

    The space opera Interstellar actually while technically not-even-close, at least demonstrated the pot-hole problem. It is the big one when there is little-to-no recourse from relativistic impacts. Unlike the movie, there’d be no imbedded meteor chunks. Just ragged holes thru kilometers of space-ship-mat

  115. № 8 – Communications

    While one might argue that the point of a generation ship is lost if it cannot resonably “talk back to Terra” over its journey, I tend to disagree: if it were completely silent, that’d be OK too. At least until it “got there”. But I’m the minority. The majority would undoubtedly want to hear back from it all the time.  

    The problem being all those potholes, and the weakness of the signal over distance.  

    № 9 – Short-list destinations

    So, where to go, me hearties? Where, oh where to go? At present, we’re (sadly) confirming Fermi’s Paradox: near-none of the recently discovered gazillion exoplanets are places we’d want to go, with what we now know about them. We’re going to have to develop WAY WAY bigger optics to be able to discern enough of the handful of high-potential exoplanets to even figure out if they have the right-mix of conditions for life. Then they have to be close enough. And so on.  

    Its a problem.

    № 10 – Ethics

    Finally, harken back to the Prime Objective. Essentially the same as the Code of Ethics for Medicine. Do no harm. And our ‘invasion’ of another star’s habitable planet’s endosphere would definitely be “harm”. How to make the ethical decision to say “fûque ’em, they’ve got nothing but worms, bugs and mushrooms”? Or perhaps its OK? Panspermia and all that!

  116. ________________________________________

    If you haven’t, there are 4 important place-holder novels that are must-read books about this range of reasoning.

    • Helliconia (Spring, Summer, Winter) Aldis, Brian
    • Four Ways of Forgiveness (Hainish cycle, Ekumen) Le Guin, Ursula
    • Rendezvous with Rama (…) Clarke, Arthru C. 
    • Foundation (trilogy) Asimov, Isaac
    • Book of the New Sun (third cycle), Wolfe, Gene.

    There are another 25 worth reading that flesh out the star-faring generation-ship ideas. Technically, Le Guin’s Hainish are the consequence of the generation-ships, hundreds of thousands of years after colonization. Helliconia is slow, dark, brilliant. It is painfully British, story-telling wise. But it holds immense water. Foundation is also post-massive colonization of the stars. It is worth reading, well … because it is so good. It is (in a way) a bit of a spoiler-alert issue reading New Sun before all the books that preceed … because THEY are so good. So memorable. 

    None of these are dystopian. Clarke alone imagines a technologically achievable, within-known-physics interstellar craft that requires no magic. Lots of technology. No magic. By itself, it is worth the read. But all 5 are together something greater than their individual opuses.

  117. Reddit habituées often include…

    — ( Kim Stanley Robinson – 2012 )
    A Fire Upon the Deep 
    — ( Vernor Vinge – 1992 )
    — ( Charles Stross – 2005 )
    — ( Peter Watts – 2006 )
    Brave New World 
    — ( Aldous Huxley – 1932 )
    Childhood’s End 
    — ( Arthur C. Clarke – 1953 )
    — ( Clifford Simak (1952) )
    City at the End of Time 
    — ( Greg Bear (2008) )
    — ( Frank Herbert – 1965 )
    — ( Kurt Vonnegut – 1985 )
    God’s War 
    — ( Kameron Hurley (2011) )
    Half Past Human 
    — ( T. J. Bass (1971) )
    — ( Brian W. Aldiss (1962) )
    House of Suns 
    — ( Alastair Reynolds (2008) )
    — ( Dan Simmons – 1989 )
    I Have No Mouth and I Must Scream 
    — ( Harlan Ellison – 1967 )
    In the Ocean of Night 
    — ( Gregory Benford (1989) )
    Instrumentality of Man 
    — ( Cordwainer Smith (1985) )
    Last and First Men 
    — ( Olaf Stapledon (1930) )
    Limit of Vision 
    — ( Linda Nagata (2001) )
    Little Faces 
    — (short story) ( Vonda N. McIntyre (2006) )
    Manifold: Time 
    — ( Stephen Baxter – 1999 )
    Neptune’s Brood 
    — ( Charles Stross – 2013 )
    — ( Samuel R. Delany – 1968 )

  118. Reddit habituées often include…

    Old Man’s War 
    — ( John Scalzi – 2005 )
    Pandora’s Star 
    — ( Peter F. Hamilton – 2004 )
    Revelation Space 
    — ( Alastair Reynolds – 2000 )
    — ( Larry Niven – 1970 )
    Sister Alice 
    — ( Robert Reed (2003) )
    — ( David Brin (1980) )
    Tales of the Dying Earth 
    — ( Jack Vance – 1950 )
    The City and the Stars 
    — ( Arthur C. Clarke (1956) )
    The Dispossessed 
    — ( Ursula K. Le Guin – 1974 )
    The Golden Age 
    — ( John C. Wright (2002) )
    The Man-Kzin Wars 
    — ( Larry Niven (1966) )
    The Mote in God’s Eye 
    — ( Larry Niven (1974) )
    The Player of Games 
    — ( Iain M. Banks – 1988 )
    The Quantum Thief 
    — ( Hannu Rajaniemi – 2010 )
    The Snow Queen 
    — ( Joan Vinge (1980) )
    The Time Machine 
    — ( H.G. Wells – 1895 )
    The Windup Girl 
    — ( Paolo Bacigalupi – 2009 )
    Year Million: Science at the Far Edge of Knowledge 
    — ( Damien Broderick – 2008 )

    … just saying. Quite a list.

  119. “…Making moving it at any respectable fraction of c very unlikely…”

    That is a good thing. Moving at any respectable fraction of c is suicidal unless you have serious magical science &tech to protect you from all that friction and radiation.

  120. Genetic diversity is not a problem for that reason, the challenge is having enough population for skill diversity. Even if you can sufficiently characterize all the skills necessary to keep an advanced civilization going, and teach them as needed to the next generation from backups, (Can’t do that right now, too much “black art” around.) there’s probably a minimum skill set you need to have live at all times.

    Also, you need enough people that everybody doesn’t up and join an apocalyptic cult, or something stupid like that. We don’t really know the minimum population, but I’m guessing it’s at least small city sized.

    We won’t be doing this until we have functioning and independent space colonies. Then we’ll do it naturally; People will just colonize outbound comets, and then give them enough of a boost that they don’t come back.

  121. By the time humanity is able to build a generation ship, cultured meat, etc. is going to be old hat. Realistically you might do chicken, fish, rabbits, etc. that have short life spans and good feed conversion. Cattle you might bring embryos, but they take a lot of space and resources to keep alive.

  122. Can you imagine the hell of spending centuries with a couple hundred other people, in a can in the void of space, with month or year long communication delays with the rest of humanity? I would seriously question the psychological feasibility of generation ships, even with SENS indefinite life extension.

  123. This is what should make investing in SENS the top priority right now.

    With enough life, a lot more things can be had, specially from the egotistical perspective of what would I see if I lived longer?

    I know that if I had an extra century or two without decaying too much, I’d like to keep working and saving money to eventually live off-world for a while. Moving from planet to planet every two or three decades seems like an attractive option.

  124. No, we’re not ready. If in doubt, just take a good long look at the international space station and the absurdity of the idea will become quite obvious.

  125. Especially when you can make things like quorm using methane and electricity in a bioreactor for your protein supply. Hell, there’s are those aquaponics loop rigs with tilapia fish and vegatables. Definitely no need to go to high order animals for long term sustainment.

    While some might make the argument about retaining animal husbandry skills through the generations, that seems a little specious since the launch crew would be dead and that’s a skill the arrival crew specifically might need, but not the sustainment crew. Sprucing up flavored protein paste seems much easier resource-wise.

  126. 500 people may not be *that* big of a problem IF the genetic diversity is there. 50,000 is typically the population lower limit if the population is basically from the same genetic stock.

  127. Use an Orion Drive.
    Grow your food in a lab[working on this tech now]
    Fusion would help since you would have a pretty abundant energy source[in most places]

  128. 1) Lab grown meat vs. barnyards and pastures.
    2) The problem with generational ships is that advancing technology will catch up to them – literally in this case. I guess you could make the second ship large enough to give them a ride or upgrade their propulsion on the drive by…

  129. You know what? I give up. I can’t write much of anything on a complex topic like this with the imposed character limit.

  130. Those look like locally sourced and built buildings and modules.

    The graphic seems to depict an asteroid being used as source of materials for a long term habitat, possibly a generational ship.

    It even seems to sport a rotational ring, where people can pass most of their time. Of course, we can’t see what’s inside the asteroid, so probably there are more rotating rings inside.

    The problem of any similar approach, is the huge mass penalty that carrying an asteroid would add. Making moving it at any respectable fraction of c very unlikely without some serious magical science &tech.

    An asteroid worldship like this would probably be in a very, very long trip* (tens of thousands of years), similar to the one of a Voyager probe, and it would need to be a legit self sufficient world for many generations of people.

    * With the added problem that these ships could arrive only to find thriving colonies that went there in faster, smaller ships.

  131. Recycling everything is doable, just very energy intensive. You heat all the atoms into plasma if necessary. Elements can be removed at different temperatures. Absurd energy expense, but doable. Well, not ideal for tungsten and some other very high temperature elements. But you just don’t build anything critical out of those, or you have ample extra.
    Is an asteroid necessary? I doubt it. Makes more sense to just bring along big blocks of elements…more of what the ship is made of, and elements necessary for life. Just as back up. A random rock, would just be a lot of extra mass slowing down the journey.

    The only recycling bit that might be troubling is human bodies/tumors/other surgically removed human parts. Human waste turned into plant mater is one thing…bodies into food is not culturally attractive. Maybe into plants that are not eaten: cotton, paper, or houseplants? I don’t know…sounds virtually impossible to keep separate unless you just freeze it or put it out an airlock.

    I think it is a given that you have to use nuclear power. Molten salt reactors sound good. Bring the hundreds of tons of thorium and uranium. Of course, you would need the means of making a new reactor and as the energy would be hard to store, I would think you would want at least 3 reactors. Where 1 is sufficient for all the real needs and can provide enough surpluss energy to make another.

  132. Or a data transmission repeater, allowing higher bandwidth, with lower total energy expenditure,

  133. A ship like this would be an agricultural paradise. It would be a like a series of greenhouses where atmosphere, dark-light periods, and even light spectrum could be tailored to the grower’s needs. Insects, and weeds should not be a problem, no need for water to ever wet a leaf(that’s how most plant diseases start).
    I’d guess that almost all crops would be “perennials” what ever that would mean in an artificial environment. Anyway, long lived plants, with many harvests mean much less work for the grower. Plant once, grow the plant to size once, harvest many crops from the same plant. It would be the perfect place for the perfect “food forest”.

  134. 500 is actually extreme overkill. I estimate that we are less than a decade away from synthesizing whole genomes from scratch. A simple flash drive could store millions of genomes, and could simulate matings and give you new genomes by the trillion. If you are actually going to have people (perhaps we never figure out how to grow people in gestational chambers), Then all you need is maybe 5 females. They might provide eggs which are then DNA substituted and implanted. You want at least 5 because you want 2 or 3 to be fertile at any given time. Though there are ways to extend fertility.

  135. Pretty sure humans will be editing their own body’s genes, on the fly, before this ship is built.

  136. Should we build generation-ships to become an interstellar species? 

    BLW: Yes, but our technology isn’t quite there yet. 

    BLW: There are a lot of challenges before we can send humans on LOLNG one-way trips to the stars.

    I think both those positions are defensibly prudent, Brian. 

    We have technology aplenty, yet we simply haven’t advanced in REAL terms enough to engage “reëngineering an asteroid” (the pretty picture) in order to drift at physics-and-energy limited speeds across the stars AND maintain vacuum-tight integrity for 1,000+ years, AND conserve-and-recycle all the atoms, elements, compounds supporting photosynthesis, oxygen-from-CO₂ generation, etc. … yep, we have plenty of technology, but not that level yet.  

    The CHALLENGES are actually fairly easy to summarize:

    № 1 – Energy
    № 2 – Ecosystem
    № 3 – Atom recycling
    № 4 – Radiation abatement
    № 5 – Technological criticality
    № 6 – Exogenous Unknown Development
    № 7 – Interstellar pot-holes
    № 8 – Communications
    № 9 – Short-list destinations
    № 10 – Ethics

    This is kind of a long list, so I’ll lay out the 10 points in the following attached comments (1500 limits!)

    Just saying,
    GoatGuy ✓

  137. It could also be useful to map the space in between star systems, any rogue planets that are found would make for a useful way station.

  138. What will they eat?

    Living creatures are known to be reliable, pleasant sources of food, self replicating and if kept properly, can last for the full trip.

    While meat and veggie cultivars in a vat aren’t so well tested in the long term. Unless you intend people to eat yeast and algae all the way to Proxima.

    The only problem I see is with big cattle, which is inefficient. But chicken and fish can be produced efficiently in big enough quantities to feed lots of people. Plants can have ridiculous productivity levels in dense, vertical crops. You mostly need energy and very good recycling of waste.

  139. You might if you were planning to actually recreate Earth somewhere else. They might like to see animals…rather than just videos of animals.

  140. Even with FTL for exploration, and personell transfer, a slowboat full of industrial capital goods would come in handy. It’s the interstellar equivalent of “never underestimate the bandwidth of a step van full of tapes”.

  141. The only reason that necessitate building such ships is to travel to another planet. It will take a long time till these ships will be viable not because of building the structure but also because we don’t know how to create long term enclosed livable biosystems. By the time we will be able to build such structures we may be able to reach other star systems very quickly.

  142. It seems unlikely that NASA would be funding Harold White’s research for nearly a decade if he was near a dead end, the advances in quantum computing and digital super intelligence that will be made in the next few years could get the Warp Drive across the finish line.

  143. I do not think muligenerational ships are the right approach, we are just trying to get humans started in another solar system. There are far cheaper approaches.
    You can grow humans after you land. All you need is gestation chambers and the associated chemicals, seeds for plant-based foods, gestation chambers capable growing about one hundred animal species. You can bring embryos…but I would go slightly different. Bring frozen eggs and then synthesize the DNA and insert that into the eggs. This is better because there is a lot of radiation in space and we need this ship to be small…and there is no good way to prevent DNA damage in a small ship. The mitochondria in the eggs may also need a DNA replacement.
    And you will need serious automation and some androids. Children will need parents. Some of the animals will also need “mothers”.
    Plant seeds, fungus and soil bacteria will also need some protection and may need some DNA replacement/repair.
    It makes the most sense to start with the plants and bacteria and such…if we need to change that atmosphere.
    I don’t think we are going to luck out and find an oxygen-nitrogen atmosphere but a nitrogen atmosphere with liquid water seems like what you would be looking for…and obviously in a temperature range that is friendly to Earth life.
    You would delay the growth and introduction of humans and animals until you get oxygen levels up. Robots can spreed seed or and place sprouts in the best habitats.

  144. By the time ships like this are an option, I am confident lifespan will be indeterminate. All ships will be single generation ships, because there will be plenty of the original crew, that are alive when the destination is reached.
    If every aircraft carrier is a floating city, these ships will be flying self contained economies, with the exception of information exchange with the outside universe. Energy should not be a problem. Fusion, or fission would both provide enough work, and waste heat to keep a population warm, and fed.
    Plants will be grown with LED lighting(or something better), but the ship will need to be able to manufacture it’s own lamps for replacement, or expansion of production. “Meat” will be cell cultures grown with plant derived nutrients. Why use plants? Because one way or another, self replicating, and repairing active nanotechnology will be needed, so why not use God’s toolkit? There will be plenty of technological challenges without reinventing that wheel!

  145. Don’t count your chicks before they hatch.

    All these studies of anomalous thrust and similar phenomena at NASA are still pretty much wildcards, which nobody knows if they will end up producing anything.

  146. Given that NASA has been working on it throughout this decade, we will probably figure out warp drive technology before we hollow out an asteroid and turn it into a generational spaceship. So the need for one as a means to settle other star systems will probably not be a compelling reason to build it, but the argument for building a mobile home to explore the galaxy and beyond will still have weight and merit, because we are a nomadic species, and that kind of life would appeal to many at a genetic level.

  147. You lost me with the need to support livestock. Isn’t it obvious that you wouldn’t rely on terrestrial farming techniques if we’re so technologically advanced we’re building generation ships?

  148. Right now or in the short term future (e.g. the first half of this century), probably no.

    We are just learning how to step properly and affordably out of our planet, with a lot of experience about living in space pending to be acquired.

    We need to learn how to build self sustainable lunar, martian and orbital settlements, also how to produce complex stuff in space and get a living out of space rocks, and develop the closed ecological systems, automation and tech required for long term survival.

    Besides what’s the rush? the Solar System looks like a big enough scenario for humanity in the coming decades, maybe centuries.

    When we have experience about living in space for several decades, and we start actually pushing towards the edges of the Solar System, with mature nuclear fusion, AI and self-replicating/repairing machinery, then manned interstellar travel could become a much more feasible prospect.

    But we can certainly invest on mapping the neighborhood with space telescopes and eventually, interstellar probes, which have less daunting technical and human requirements.

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