Q&BA: Can we build a space habitat?

By Phil Plait | April 4, 2012 2:30 pm

Every week (or so) I do an interactive live video chat on Google+ where people can ask me questions about space and astronomy. I call it Q&BA, and it’s always fun to hear what questions are on people’s minds.

I recently got a great question: "What do you think of the concept of a space habitat? Is it possible to replicate Earth’s environment in space?" I really leaned into this one — I’ve spent some time thinking about it — so here’s my answer:

That last minute or so is important to me. One of the reasons I do any of this — write, speak publicly, and share my joy of science — is to help increase public perception of science and space, and hopefully to help inspire people to be excited about space travel the way others inspired me when I was younger. I imagine this will be a recurring theme in future Q&BAs.

I have an archive of Q&BA links and videos. Take a look and see if there are other ones that tickle your imagination.

Related Posts:

Q&BA: The Science of Science Fiction
Q&BA: How does a gravity slingshot work?
Q&BA: Why spend money on NASA?
Q&BA: What happens if you are exposed to the vacuum of space?
Q&BA: Getting kids into science

CATEGORIZED UNDER: Astronomy, Piece of mind, Q & BA, Space

Comments (48)

  1. llewelly

    Phil, in your argument for why we should build space habitats, you assume it is feasible to build independent space habits, which do not require resupply from Earth.

    In fact there are a huge number of problems when have never been solved, from basic ones like preventing slow leaks of water vapor from gradually turning the habitat into a desert, to complex ones, like how to construct a self-sustaining ecology which supports edible plants (to say nothing of humans!)

    And for true independence, a great deal of industry is required. There has never been a space craft which has repaired itself with a part it made in space – every space repair or upgrade has been done with parts and technicians lofted from Earth.

    So here’s my question: What makes you think these problems will be addressed, let alone solved?

  2. First of all, you have these at the most inconvenient times, so thanks for recording them. Although I have to wait until I get home to actually watch them, adn the anticipiation always kills me! 😀

    @Ilewelly (#1), I have not see the video, so I don’t know exactly in what context your question is, but just off the top of my head:
    – Water is PLENTIFUL in space if you know where to look! While a leak isn’t a nice thing, given the technology to build a large colony in space, moving icy objects around to serve as a water farm is no problem.
    – Ecology is a problem we’re working on. Right now I don’t think we can even start to say we truly understand ecology enough to make any definitive answers to this, but we’re pretty clever apes that may manage to figure this out. Again, if there is a colony large enough, we may start to actually figure these sort of things out because of the colony itself.
    – True independence I think again would depend on the size. A large colony could distribute functions to several nodes, so there could be factories and manufacturing capability to make the things that we have traditionally had to sling out of the planet’s gravity well.

    The easiest answer to your final question is that us mostly hairless apes have already imagined the solution to these problems. With enough resources, imagination, technical know how, and practice, they are solvable. No one ever thought we’d solve the problem of powered flight, yet now it’s an occurence so common no one can imagine thinking of it as an “imposible” idea.

  3. Ok I’m not getting why I am watching two versions of you in a Google+ hangout at what seems to be a blurry 15 fps. Really close to the camera. Take a cue from Charlie and be so cool like with the changing of stuff. And things! Most importantly things. Like framerate. Or close-upness to the camera. Or whatever.

  4. I was wondering if a space station/craft could be grown in space instead of built. hyper growth crystal or rapid growing mineral or something we could hallow out an use as a shell?

  5. Evan Guiney

    I really like the last point you make, that self sustaining space colonies are likely to be essential to the long term preservation of the human species. I’m actually pretty optimistic about our species survival (quality of life may be another matter) here on this planet, but when one considers the many low probability events that could wipe us out, with enough time even low probability things are basically guaranteed. But if we build N independent space stations, the chance of humanity going extinct becomes [low probability]^N! And that’s a comforting thought! So given that the kind of space station you describe is roughly on a technological par with a mars mission (give or take an order of magnitude), why isn’t *this* higher up in our national space priorities conversation? I never even hear Niel deGrasse Tyson talk about this! Given our species’ fascination with apocalypse and immortality, what better motivation for space exploration could there be?

  6. Jay

    Rendezvous with Rama!

  7. gopher65

    I agree that we have or will have in the near future the technical skill to build a largescale rotating habitat (if they’re designed properly, at 10km across (or bigger) they create their own radiation shielding too!, so even that’s not a problem).

    The real issue is infrastructure in space. We live in a deep gravity well, so it isn’t (reasonably) possible to launch enough prefabbed stuff into space to build something that big. Heck, even on Star Trek they don’t do that, because it simply isn’t logical.

    So since we can’t launch the components into space to build something like this, we need to manufacture them in space. But prior to that we need to refine the compounds and elements we’ll need. But before we do that we need to separate out and purify the base materials and ores we need. But even before that we need to mine the materials. But first we need to build the mines.

    That is a *lot* of infrastructure we need to build, step by step, before we can build the habitats we need to survive in space over the long term. I’d guess that it will take several hundred years to build up that much infrastructure.

    It’s like the resettling of the Americas (once they’d been mostly emptied by nefarious means:P). They had the technology and population to settle the continents and build cities immediately, but they lacked the local infrastructure to do it quickly. So it took hundreds of years. Same thing here. Lack of local infrastructure is the killer.

    (Incidentally, this is the same chicken-and-the-egg problem facing Africa today. They need to build a thousand little pieces of infrastructure before poverty will drop to the point that the current insane level of violence will start to decrease. But in order for that infrastructure to be built, long periods of relative peace are required…)

  8. Michael Simmons

    I agree with Phils vision.

    However I think people underestimate the problems of radiation and high velocity meteorites for large O’Neill Colony outside of the earth magnetosphere.
    Have studied been done on this?
    It only takes one small asteroid to completely kill everyone on one. I would not be making them one large open plan enclosed space.
    How do these things fare against solar CME’s?
    Can you really have huge transparent windows to let the sunlight in?

    Personally I’d rather see underground colonies on the moon, mars and large asteroids.

    Even with large self sustaining space colonies we can still be wiped out but supernova and GRBs.
    Those vast O’Neill Colonies just become giant tombs.

    One other comment I’d like to make.
    The 2/3 of the world is covered in water. How many permanent underwater habitats of any kind do we have? Zero. Perhaps we should start here first.

  9. Gary Ansorge

    Manufacturing in space will require…

    1) tele-operated robots(to do the hard vacuum/radiation prevalent/exterior work)
    2) AI, human guided robotics to do the mining.
    3) efficient energy sources, from power sats to nuclear fission/fusion power
    4)efficient, cost effective space access(mag lev accelerators, nuclear thrusters, space elevators)
    5) 3-d printing for in situ manufacturing

    …and of course, resources(water, metals, etc) and the closest such resource to us is the moon.
    Most of these techs are in early stage development and, as with all things technological, as the market for these grows, so will the tech become more and more usable and we get them faster and faster. It’s economic positive feed back that will drive this development. Once someone gets out there and is serious about such development, the tech will grow and make it all affordable.

    4. Brent

    My favorite colony design is to just hollow out an asteroid. Built in meteor and radiation shielding from the asteroidal material. Lots of room inside.

    Gary 7
    PS. Thanks Phil. I’ve been waiting for you to address this issue.

  10. Outcast

    Something to consider about building a space station: The way we do it today, namely building modules on Earth and connecting them like legos, while useful as a starting point is inherently limited. When we have the chance, to build something in space using materials and components from space (with as little as possible sourced from Earth), we can build stuff bigger and much more capable.

    Of course a colony like this would likely not be independent. In order for something like this to happen it needs to be economically sustainable, such in R&D, manufacturing, tourism, or some combination thereof. That would involve continuous trade.

  11. TheVirginian

    First, I’ve long thought that something like this is the only way to ensure the long-term survival of humanity. Now that global warming is certain to have very serious, potentially devastating conseqauences for civilization itself, something like this might be the only guarantee of keeping some portion of “civilization as we know it” alive.
    Second, I’m sure Phil knows this idea has been used in science fiction tales, usually “Dystopias” where something goes wrong. Heinlein did it; I think Brian W. Aldiss did it; I recall the original Star Trek had an encounter with a traveling “habitat” of some type (I think it was on a planet en route across interstellar space) where a computer had gone berserk and messed things up. (Too lazy to look it up to verify it.)
    Third, significant problems await. We need a much-deeper understanding of the complex interactions of bio-systems. Just replicating our salty oceans would be a monumental feat. The last I read, we cannot produce artificial sea water that keeps sea creatures alive long-term. (This might be out of date now.) Construction would require very advanced robotics and mining of asteroids, even small moons from other planets to supply construction materials. In a few decades, advanced AI (or even real computer intelligence) and advanced materials (Buckyballs, possibly) might open doors to develop the necessary technologies.
    Therefore, I am hesitantly optimistic. If we can get through the very bad period of global warming that’s coming without a collapse of civilization (and we are also heading toward serious energy production deficits) and have the social willpower to push for construction of some type of space Habitat, it might come about. There are a lot of “ifs” involved in this, and the biggest one is: If we can get some real leadership in this country that looks at the long-term needs of humanity, not just the next quarter’s profits.
    Finally, if cut off from Earth for some reason, it would require the development of a “spaceship ethics” by its inhabitants. They would have to restrict reproduction voluntarily and prohibit, not just by law but by custom, any actions destructive to the environment. Laissez-faire capitalism and Ayn Randian capitalism would be suicidal. Gee, kinda like what we’re doing now to our planet, exhausting its easily-recovered resources, draining its cheap energy supplies and wrecking its environment. Perhaps the consequences of this destructive behavior will create a “spaceship ethics” to save the Earth and give us the psychological frame of mind for a space Habitat.

  12. Back when we still had a space program I had a chance to talk to a NASA PR scientist on a local talk show. I asked him why they let the big external shuttle tanks burn on reentry. They could just deposit them by the space station and use them for storage and/or habitats. His answer? “We weren’t tasked for that.” I told him I understood that, but I was asking HIM if he thought that might be a good idea. Have the raw materials in a relatively stable orbit where you can use them to build anywhere you want. “We weren’t tasked for that.”

    That was the moment I knew NASA was doomed.

    We could already have a starter habitat up there. Someday we will, but I don’t think it will happen until we get good A.I. Then the robots can build more of themselves until there are enough of them to build space condos for us.


  13. amphiox

    So here’s my question: What makes you think these problems will be addressed, let alone solved?

    For the simple reason that there is no evidence to suggest that these represent any sort of fundamental barriers, with any laws of biology, physics, or economics precluding their eventual solution.

    They are just engineering problems.

    Finally, if cut off from Earth for some reason, it would require the development of a “spaceship ethics” by its inhabitants. They would have to restrict reproduction voluntarily and prohibit, not just by law but by custom, any actions destructive to the environment.

    Not necessarily. If the space habitat were given the capacity to move (for this you just need an engine – any engine of any speed. The self-sufficient nature of the vessel means there’s no absolute time limit for any sort of travel), and the capacity to harvest and process resources from space sources (like comets, asteroids, and the like), the space habitat would de facto be capable of growth and self-replication in response to the needs of growth. You fire up your engines, trundle up to a resource rich asteroid or KBO, harvest all the necessary resources to build a second space habitat, move your excess population over, and then part ways. If any individual habitat runs into environmental disaster, it will have replacements.

    And besides, cultures on earth today already practice voluntary restriction of reproduction, and already have voluntary restraint from environmentally destructive activities. It’s just that these voluntary restraints are not absolute. But the earth has excess carrying capacity capable of absorbing a certain degree of environmental stress. A robust space habitat would also be designed to have such excess capacity to absorb environmental stress.

  14. Cantareus

    Computers are developing so much faster than our ability to colonise space. When we can colonise space we wont need the vast open spaces an O’Neill Cylinder provide. It will be far cheaper to build cramped colonies and simulate the open spaces. The vast amount of power and resources available will mean that space colonies will allow for much more open systems than the earth. They will move from asteroid to asteroid using what they need and discarding what they don’t, it’s the human way.

  15. StubbyGB

    One thing that I havent heard discuused is the problem of radiation in space. We hear all the time about how the earths atmosphere/magnetosphere protects us from solar radiation, and how its a problem for people in space.

    I have seen suggestions that astronauts on a trip to mars would have to ‘hide’ in what amounts to a protective bunker whenever a solar flare pointed in their direction.

    With potentially thousands of people on a habitat, this doesnt seem practical.

    I was ‘pie in the sky’ wondering if a future form of solar panel could be used as a form of ‘shield’. after all the idea of these panels is to collect radiation. I dont know how much of the EM spectrum is currently collected, but I see no reason why it would be limited to visable light only. If their effective range could be expanded enough, not only would it mean more potential energy for the habitat, but more shielding also.

    Just throwing it out there.


  16. #14 StubbyGB:
    If we ever develop the technology to build O’Neill colonies, then radiation shielding will be a trivial problem. Construct the habitat’s hull with two shells, with a couple of metres gap between, and fill the gap with rocky material – and there’s your shielding. Assuming that the construction materials are obtained by mining a captured asteroid, the waste material which is left over can be used for the shielding.
    If we’re talking about an O’Neill Island 2 design – i.e. cylindrical, with alternate strips of “land” and windows, then this shielding would protect the inhabitants against radiation coming through the hull below their feet. For that which comes from above their heads, through the opposite window region, they will be protected by a few kilometres thickness of atmosphere.

  17. @StubbyGB (#14), as amphiox (#13) said, those are engineering problems. Not fundamental problems in physics such as FTL. If we had the energy, could we generate some sort of protective magnetic bubble? That’s just a crazy idea off the top of my head (beyond the simple meters of rock solution).

  18. Nigel Depledge

    @ StubbyGB (14) –

    Erm . . . even easier than Neil’s sugestion. Use on-board power to generate a pervasive magnetic field. After all, the Earth’s field isn’t strong and it seems to do a reasonable job protecting us.

  19. Earth 2, which was a sealed environment on the ground (Earth 1, we live here), had some technical issues. One was that the floor was concrete, which exhales carbon dioxide. (There are now cheap concrete formulations that do this much less, if at all). They had to pump in some oxygen (not sure how that helped). We’d want to get these technical issues solved, and it seems cheapest (but not that cheap) to do it on the ground.

    In space, we’d also really want to have an effective radiation shield. Perhaps a meter or two of water all the way around. It’s quite a bit of water. Spining the water would require quite a bit of structure. One idea is to have the water, but not spin it. The habitat inside the non-spinning water would spin for gravity. But then you don’t have really cool portholes to look at Earth. You could still look out of the ends of the cylinder, be it pancake, tuna can or pencil.

    We’ve evolved with gravity and with certain radiation protection. The ISS solves neither problem. NASA gravitates towards mitigation strategies. I keep hearing claims that we can get to Mars in a decade or less. That we’re closer to getting to Mars than we were to the Moon at JFK’s speaches. I don’t believe it. We’d have astronauts with weak bones, and who are practically blind on Mars. And even if artificial gravity is available in flight, it’s not clear if Mars has enough. IMO, don’t send them if they aren’t coming back.

  20. Tony

    I’ll believe permanent locally-sustained settlement of space a few decades after we have permanent locally(!)-sustained settlement of antarctica or the core of the gobi desert or the bottom of the ocean.

    I’m not holding my breath.

  21. John H

    The technical challenges involved in building habits off the Earth are almost certainly solvable, but to minimize them is unwise. We’ve been engaged in picking the low hanging fruit to this point, and are now just starting to look at the less easily reached branches. That we evolved in gravity well with certain environmental parameters is an inescapable truth, and re-creating a salubrious ambiance that can support its own needs as well as ours in a sustainable fashion is not something to be passed off lightly. We have solutions for this in the same sense that book of airplane pictures is a solution for an air transport issue. What we have are nice pictures and names for them with a seriously deficient level of detail. And, assuming that any of our engineering fantasies actually solve that primary problem, that would just open the door to the bulk of the work that will have to be done. Anyone involved in the ordinary engineering that keeps our civilization running knows how difficult the most common processes really are. The effort required to get a familiar item like an automobile to market, let alone support it and provide the necessary infrastructure, would astonish most people. Translate any of the processes that support us with shelter, goods, and services to a lethal and unforgiving environment that lacks every basic need, and you will encounter both technical and economic problems that certainly daunt my imagination. And here is where the pachyderm really enters the room. The cost. The mind blowing number of zeroes that will be on the invoice for this adventure. It will put all of our previous efforts into perspective as the petty cash line items that they really have been. When we start asking our neighbors for military grade cash to pursue this path, then the questions will become much more to the point. And that point is that the real roadblock will always be an economic one. It takes an entire planet to make most of what we consider our advanced technology an economic proposition and there are solid arguments that the simple economies of scale will prevent any space habitat from ever being self-reliant, and that we will likely have to commit to continuing support for as long as they exist. We have little evidence to oppose this view. At this point there is no space economy any more than there is a mountaintop economy. Both are used for communications purposes, but neither is currently sought for any proven economic purpose beyond that. While there are some material spin-offs from our efforts in space, there is little evidence that the same advances could not have been achieved with a smaller investment in research in the materials and communications sciences. The advances in astronomy and astrophysics are undeniable, but apart from the few of us that can appreciate those advances, who would agree to pay significantly more for that kind of payback? Other than the hand waving fantasies that comprise the economic models so far proposed, what is our real and current reason for asking people to engage in the pursuit of off-world habitats? Magical economic thinking will not serve this cause well. If we can’t be a lot more creative and sensible in our arguments for seeking an off-world future, and can’t come up with real economic reasons to go there (real to the people that will have to foot the bill, that is), then it’s more likely that we won’t.

  22. amphiox

    StubbyGB, the radiation shielding problem is actually a secondary effect of a propulsion and lift problem. Radiation shielding is easy, it’s just heavy, and requires lots of energy to lift into orbit. So by advancing propulsion and lift technology, you pretty much automatically solve the radiation problem.

    Indeed, the mass required to even try to build a self-sustaining habitat is probably sufficient that the habitat itself would serve automatically as radiation shielding. A few meters thickness of water is pretty much sufficient. You could simply put your reserve water tanks as a shell around the habitation portion of your vessel, and you’re golden.

  23. amphiox

    IMO, don’t send them if they aren’t coming back.

    Perhaps. But as a thought experiment, consider a one-way mission to Mars. You send the crew with life support that will last them say a year or so on Mars, plus the machinery and technical capability (and communication lines with earth) that would allow them to build, within that year, their own habitat. And then they stay there for the rest of their lives (or until the ability to mount a return mission becomes feasible in a decade or so, or until they themselves figure out how to mount a return mission from Mars to Earth!). Let them go knowing before hand that if they end up failing in making that livable habitat within that starting window, they die. They’ll get a sad eulogy and a parade and a hero’s monument back on earth.

    I don’t think you’d lack for volunteers willing to go on these conditions. In fact, a lot of humanity’s early exploration was done in this fashion. One way trips. You get to your destination with the intent of figuring out how to survive when you get there, with no guarantees that it will work. You either make it there and live, or you don’t and die. You never go home.

    In fact, even a one way Mars mission in which death was guaranteed in a year or two after initial life support runs out might still get volunteers! (Though I doubt we as a society in our current political climate would support such a mission).

  24. amphiox

    John H, I have a suspicion that in order for space colonization to work, a space economy will have to precede any large scale space colonization attempt. Resources will have to found in space first, and then people will find economic incentives to try and go out there to collect and life off those resources. The initial public supported (nonprofit driven) phase will only be able to bootstrap the enabling technologies. Beyond that the costs are prohibitive and there won’t be the political will. Even if economically possible, it will never win enough support against all the other demands for resources in the marketplace of ideas.

    If the space economy successfully boots up, then space colonization will pay for itself. If the space economy doesn’t successfully boot up, in all likelihood we won’t be leaving this rock.

  25. amphiox

    what is our real and current reason for asking people to engage in the pursuit of off-world habitats?

    Actually I don’t think we actually have a current reason. The enabling technologies simply aren’t in place yet. One cannot even begin to make reasonable economic arguments based on hypotheticals of future technology. The real current economic argument has to about whether or not those enabling technology streams are economically feasible to pursue. And probably will have to be pursued for goals that are earthbound, not with a view to potential future space activity. Only after we successfully get the enabling techs bootstrapped will it be possible to consider the economics of future exploration in space.

  26. John H


    I think that is likely correct, but it leaves a long chain of “ifs” that have to work out favorably. It certainly changes the process from the directed efforts of the current programs to something that will have to occur as a byproduct of general technological and economic progress. Let’s hope we have the time and resources needed for that to occur.

  27. Rayceeya


    Short answer is yes. Scientifically possible, but now it’s an engineering problem.

    It’s like when Jules Verne wrote “From the Earth to the Moon”. They knew it was possible, but it took another hundred years of science and engineering to make it happen.

    The math is all there, but the materials, and physics needs to catch up.

    Hope I live long enough to see it.

  28. Rick

    Great talk Phil. I am what you would call “interested in the universe” but not interested to the point that I could put the endless hours of research in to discover these answers on my own. I appreciate how you take something as complex as “can we build a space habitat” and give a straightforward, easy to understand answer.

    Thank you for putting these together. Your blog has a lot to do with why I got interested in space in the first place. The more I learn, the more I want to learn. I love it!

    Thank you!


  29. Scenario_dave

    If you can build them in space and make them mobile you could reach the stars. If all they need is fusion power to provide energy and a supply of raw material and they could eventually travel at say 1% of light speed, they could make it to another star.

    Step 1: reduce the cost to get into space by an order of magnitude or 2.

    Step 2: Find something in space that makes someone a lot of money. Medicines that can only be manufactured in micro- gravity or microchips or … something low mass and very valuable.

    Step 3: Build an economy with a bunch of stations in orbit making a profit.

    Step 4: Mine the belt for raw materials for large scale building in space. Or maybe divert an asteroid to lunar orbit for raw material.

    Step 5: Build mobile habitats in space so people can start living permanently in them, have children, grow up in space. The habitats are their homes.

    After a while when we got good at building them, they could get big and mobile. Since they’re self sustaining except for some raw material replacement, they could take 20 years to get someplace. You’d never leave home. Your family and friends travel with you. The time of travel really doesn’t matter.

    If each habitat held 10,000 people and 50 traveled together that’s 1/2 a million people. If one habitat fails, the survivors can move to another habitat in the pod. Each habitat can specialize, with at least a couple with every important skill in case of disaster. Pods of habitats move out to the belt. Build new habitats. If each group built a couple of new ships a year, they’d double in thirty to fifty years depending on how often you’d have to scrap the old ships. When there are too many ships in one place, the group would split and they swarm. Moving further and further out over the years. People migrate out from earth and earth stations to help fill the habitats.

    After a few hundred/thousand years, you’ve got thousands of habitats in the outer system. Just find a good sized rock with the right raw materials and move a swarm to it. If they can eventually get their speed up to 1% of light they could travel for 25 years and go a quarter light year, and find a good rock to settle. Stay a few years build new ships. More swarms come in. Place gets crowded. Swarm to the next rock another quarter light year further out. After a thousand years, they’re at another star. But nobody ever traveled more than 25 years at a time and they took their homes, family and friends with them. Each pod has hundreds of thousands of people so people don’t feel isolated.

    Technically very difficult. But If we start now small scale, and society doesn’t crash, where will we be a hundred years from now.

  30. amphiox

    The scenario outlined in #30 is more or less exactly how I envision humanity will spread to stars. Or more precisely, it is I think the only reasonable way that a species like humanity could colonize the stars. We will either surmount the technical and economic challenges, or we won’t. And if we don’t, then one day we will go extinct on this one small rock.

    (I think that it is just possible for one of the early steps to be bootstrapped for non economical reasons, by say a single wealthy fanatical government, or cult, or private nonprofit organization. Or even by one powerful individual. But it will not be sustained unless it rapidly catalyzes economically viable followup.

  31. Michael Simmons

    I see.. so a couple of meters of water can replace the earth’s magnetosphere and 100km of atmosphere.. .
    So when you have 100’000+ people in a large space habitat those 2m of water will save them from the next Carrington super flare?

  32. @ ^ Michael Simmons : How about a magsail? I’ve seen a good design that looks like it would work pretty well as both a means of protection and propulsion on page 79 Starbound (Time-Life editors,1991) which was proposed by Robert Zubrin and Dana Andrews.

    @6. Jay : “Rendezvous with Rama!”


    Deep Space 9!

    The original Brick Moon!* 😉

    Yep, there’s certainly been some good fictional space habitats and space stations to inspire and give ideas on what we may one day build and create and live aboard. 8)

    @31. amphiox :

    The scenario outlined in #30 is more or less exactly how I envision humanity will spread to stars. Or more precisely, it is I think the only reasonable way that a species like humanity could colonize the stars. We will either surmount the technical and economic challenges, or we won’t. And if we don’t, then one day we will go extinct on this one small rock.

    Yes, I broadly agree with that too -especially the last part. If we fail to expand into space, toleave the cradle that is Earth, we are sooner or later doomed to extinction. I hope we choose wisely and keep progressing.


    * The very first fictional space station featured in and the eponymous subject of a short story written by Edward Everett Hale in 1869. Click on my name here for its wikipage.

  33. TheVirginian


    I will agree with you if I accept the premise that a space Habitat is either mobile enough to scavenge resources or has ships capable of harvesting such resources. However, even then a Habitat likely would require some type of internalized, cultural restraints to prevent growth beyond its ability to expand and actions that are damaging to its self-reproductive systems. If expansion of an original Habitat or construction of new Habitats is slower than population growth, then there must be self-restraints built into the population’s culture.
    Also, I usually try to construct (as a thought experiment) a mission to colonize another star system, and that would put a major barrier into growth of a Habitat’s population and its people’s activities in order to survive generations of life/death in order to reach a habitable star system. (Barring hypothetical technologies such as using some advanced power source to create matter resources, a la Star Trek: Next Generation replicators). So your argument is correct IF a Habitat has access to sufficient external raw materials. Otherwise, it’s neo-Puritanism. :)
    Note: I like #30’s idea, as it solves the problem of major systems failure on a single Habitat, although such a multiple-Habitat mission would require a good bit of resources that might not be as easily obtained from moons or asteroids as some people imagine. Likely, the multiple Habitats would need to be constructed either in orbit around Pluto (weak gravity well at the Solar System’s outer gravity well) or in some advanced space base in a Plutonian-region orbit. (One advantage to this scenario is use of Kuiper Belt asteroids/planetoids for mining.)

  34. Mike Saunders

    No, this is not an engineering problem. It is an economic problem. The amount of energy to capture and control the path of an asteroid is huge! Energy is money. Plus you get diminishing returns. The more potential energy you loft into space, the more kinetic energy you need to get it there.

  35. Scenario_dave

    Mike Saunders @35

    Yes the energy is huge. It can be worked around. Pick the right small asteroid with volatiles you can use for fuel for multiple robot controlled ion drives. Because no people are on it, it can take 20 years to get to Lunar orbit. Move multiple small asteroids at a time. Aim for lunar orbit so if something goes wrong it will hit the moon, not the earth. You might have a couple of manned teams setting up three or four asteroids a year or it could be robot controlled from Earth. Once they start coming in, you’d have a constant supply of raw material. Expensive at first, probably government sponsored but profit making once the raw materials start coming in.

    Getting the system started is the big economic problem. Once its started, its self perpetuating.

    The Virginian @ 34

    I think the problem would be lack of population growth. I’m anticipating that the standard of living for people in habitats would be pretty high. If you look at developed countries with a high standard of living most of them have a population growth without immigration that’s below replacement rate. I was anticipating that as the habitats in Earth and Lunar orbit get crowded, people would move out and new people would move from earth to the orbiting habitats.

    Also each habitat would be kept at 80 to 90% of maximum capacity so they could act as life rafts for the others. If one needs to change an engine which will take several months and could be dangerous, either move everyone to a new habitat or distribute the population between 10 or 20 other habitats while the work is going on.

    Trading necessary rare raw materials between pods would help solve the resource problem. Major mining bases on dwarf planets, moons and larger asteroids could mine a lot of raw materials without the deep gravity well of earth getting in the way.

    Specialized habitats within a pod would solve some problems. Some of them would be bases for smaller more mobile ships which would be used in mining, trade, etc. Some habitats would build new habitat parts for repair, trade or construction. A couple of more pods could be education oriented, colleges, teaching hospitals etc. A lot of education would be done on-line but some things need to be taught in person. Some would have few homes but would store raw materials, ships, mining equipment, spare parts, etc. when moving. A few more would be food producers. All pods produce some food but specialized food habitats allow for food production on a larger scale allowing for more variety. All of the absolutely necessary products for survival would be produced within the pod but every pod would have a few habitats dedicated to producing stuff for trade purposes, special food, advanced training facilities, entertainment, specialized ore processing for very rare raw materials, etc.

    Each pod acts like a city with its surrounding farms. Humanity would essentially be going back to a city state form of government. Each pod would have its own unique culture and government because people would be moving much more freely between the habitats within the pod that between pods.

    Michael Simmons @32

    Aren’t solar Flares directional? A small group of habits is very vulnerable. Tens of thousands spread in all different directions are unlikely to be all hit at once. Natural disasters kill people all the time. A Carrington super flare would be to space dwellers as a hurricane is to people on earth. Each pod of habitats is independent of every other one except for rare raw materials and luxuries so destroying a few wouldn’t hurt the rest too badly. A major disaster killing thousands of people occurring every hundred or hundred and fifty years wouldn’t destroy a robust widely distributed civilization.

  36. amphiox

    However, even then a Habitat likely would require some type of internalized, cultural restraints to prevent growth beyond its ability to expand and actions that are damaging to its self-reproductive systems

    The same restraints on population growth existed for hunter-gatherer populations for the vast majority of humanity’s existence. The advent of agriculture provided a partial, temporary, and in the grand scheme of things, brief, reprieve from these necessities. I am relatively confident that human culture is sufficiently flexible to surmount this challenge when it becomes necessary.

    After all, it is not as if this was something we haven’t done many, many, many times before.

  37. amphiox

    Also, I usually try to construct (as a thought experiment) a mission to colonize another star system, and that would put a major barrier into growth of a Habitat’s population and its people’s activities in order to survive generations of life/death in order to reach a habitable star system. (Barring hypothetical technologies such as using some advanced power source to create matter resources, a la Star Trek: Next Generation replicators). So your argument is correct IF a Habitat has access to sufficient external raw materials. Otherwise, it’s neo-Puritanism.

    The restrictions are most marked if one envisions a big interstellar mission, starting from deep within the gravity well of the home star system, such as a launch from a planet like earth.

    However, in the scenario described by Scenario_dave, this is not what is going to happen. Instead, we are going to see a slow diffusion of self-replicating habitats through a star system, until the star system is essentially filled all the way out to its outer comet shell/Oort Cloud. This is over a light year out from the central star. The outer shells of the Oort clouds of neighboring stars come pretty close to overlapping. An interstellar mission will then be a transit between an outer Oort cloud object from one star (that object being the resource harvest site for the habitats), to an outer Oort cloud object from another star. And the distance between them will only be fractionally greater than the distance between any two Oort cloud objects within a single stars Oort cloud.

    And in the scenario described, migrations between these Oort cloud objects within a single star system will by this point be routine. So the hop over to the next star will likewise be more or less a routine event.

  38. amphiox

    Likely, the multiple Habitats would need to be constructed either in orbit around Pluto (weak gravity well at the Solar System’s outer gravity well) or in some advanced space base in a Plutonian-region orbit. (One advantage to this scenario is use of Kuiper Belt asteroids/planetoids for mining.)

    Again, don’t think Pluto (which is inner Kuiper belt), think outer Oort Cloud.

    Or basically, we won’t be going from Pluto to the next star. We’ll be using Pluto as a staging area for going into the outer Kuiper Belt (which will range out in distance to several times the distance of Pluto’s orbit), and then from outer KBOs to the inner Oort Cloud, and then from inner Oort Cloud objects eventually to outer Oort Cloud objects. And then, only finally then, do we go to the next star.

  39. amphiox

    No, this is not an engineering problem. It is an economic problem.

    If you can point to a series of off-the-shelf, available for immediate purchase technologies that, together, make it feasible, with the only barrier being that the cumulative cost of all those tehcnologies being prohibitive, then it is an economic problem only and not an engineer problem.

    Otherwise, it is both. (Pretty much every engineering problem is also an economic problem, since solving engineering problems requires money….)

  40. amphiox

    I see.. so a couple of meters of water can replace the earth’s magnetosphere and 100km of atmosphere.. .

    In a word, yes. (So long as the water is protected from UV dissociation and subsequent loss, which it will be by the hull material that contains it.)

    Solar radiation is actually only a problem for land life. It’s not and never has been a problem for marine/aquatic life. A few meters below the ocean surface, there’s essentially no stellar radiation exposure.

  41. amphiox

    The effect of a flare will also of course depend on distance. For a habitat out in the Kuiper Belt somewhere, it’s doubtful that even the largest flares will be much of a worry.

  42. Scenario_dave

    What would we use the first one for?

    1) A a transshipment point. Everything gets shipped from earth to one big rotating station and then shipped from there by a true space ship. Some would be small robot controlled ships to ship small packages. That way you have every shuttle up full and you have a central point to store vital spare parts. Need a 1 kg part. Have it shipped to the habitat. Put it in a small automated space ship. Launch it towards the destination. It fly’s itself there. Then send the small ship to the next place that needs it. All of this happens in earths orbit at first.

    2) A place to acclimate to zero G. The apparent gravity would change from floor to floor.
    Some people take a while to get used to zero g. Going from .5, to .3 to .1 to .01 to 0g might be easier.

    3) You could rotate crew from zero G stations to a station with simulated G. That way they could stay in space longer while minimizing some of the issues on the human body that zero G has long term. This avoids the expense of sending new crews all the way from earth every six months. Someone might stay up for two – three years. Two months in zero G, one month in .7 G, two months in zero G etc.

    4) A hospital. It might be difficult for many medical procedures in zero g. Or zero g might help some medical procedures.

    5) A hotel. Want to go into space but afraid you’ll get sick in zero g?…

    Once you’ve got the first one, people could live on it indefinitely.

    Second point.

    How would society change in our slow spread to the stars? Habitats in the deep Oort Cloud could be 50 years travel from earth by the fastest ship. It would take a thousand years to travel to the nearest star by this method. The nearest star is 4 light years away. If we reached several stars in different directions the furthest points would take 8 – 10 years to send a signal by light and 16 to 20 years to hear back. Their last common ancestor would be 1000 years in the past. Would we split into separate species after a few thousand years more?

  43. Gary Ansorge

    27. John H

    Gerard O’Neilles studies started 40 years ago and what his team came up with as an economic rationale was simply energy. Solar energy at earths surface, at high noon, on a good, clear day, is about 350 watts/m^2 and that’s for only a few hrs/day. In space, at earths orbit, it’s about 1350 watts/m^2, available 24/7/365. Generation of electricity on earth is currently a multi trillion dollar/yr business. Transmitting that much energy to earth via “radio waves” is relatively easy. Building the power sats from lunar raw materials is doable but the infrastructure costs are in the multi hundred billion range. If power sats are the economic rationale, at least you have a POTENTIAL economic return but, who but a government(or several, working together over a 20 year span) would be able to spend such sums? THAT’S the real question.

    Gary 7

  44. Scenario_dave

    I thought of power but I didn’t use it because of the high start up costs.

    Zero G manufacturing.

    What if you could make a room temperature superconductive material in zero G? Or a cure for cancer or baldness or many types of colds? Or the newest microchip 100 times faster than any made on earth? Transparent aluminum? What’s produced must be expensive and light to make it profitable to ship raw materials from earth and finished products back.

    Who predicted tobacco when the new world was settled? (Hopefully the product we find won’t slowly kill us.) We don’t know what we can make ,yet.

    Once we’ve found a few profitable products and built up an infrastructure in neo, it would be easier to take on bigger projects like power, especially if we can divert close earth objects into lunar orbit for raw materials.

  45. Gary Ansorge

    45. Scenario_dave

    Physicist Mike Combs (of the Space Studies Institute) said studies of power sat costing indicated the break point at 30 power sats, as in, if all we ever built were 30, it would be cheaper to just launch them from earth. Beyond 30, scale increases would allow a reduction of per unit construction costs by building them in space from lunar material.

    Returning refined metals and such from orbit to earth is easy, since it’s all downhill. We just add nitrogen bubbles to the molten metal, making the foamed metal lighter than water, so after dumping them in the sea, the pieces that survive re-entry will float and are easily retrieved.

    Transparent aluminum is just clear sapphire and we can make that here. Perfect crystals are easier to make in free fall but near perfect is what we already have.

    Energy is about the only thing that is truly cost effective but it only works if we’re willing to dedicate a significant percentage of the worlds GDP to creating the infrastructure.

    …catch 22…

    Gary 7

  46. Scenario_dave

    46. Gary Ansorge

    You may be right but how much experimenting have we done in space? Much of what we know about what we can manufacture in space is based on earthbound hypothesis not actual experiment. I don’t like assuming it can’t be done until we actually do the experiments.

    My point was that we’re not going anywhere in space until we find something up there that’s profitable enough to let us start building an infrastructure. Once we get an infrastructure, we can make more things profitable.

    If human kind only looked at what we can do now and didn’t experiment, we wouldn’t have any technology.

    Transparent aluminum is a star trek reference, which you probably got. :)

  47. Bob Perry

    John H @ 22 said . . . come up with real economic reasons to go there . . . and Gary @ 46 quoted Mike Combs that the [lunar and space based] infrastructure for building SBSPS (space based solar power satellites), including space habitats, would require 30 SBSPS to be advantageous over earth launched. A new white paper posted by NSS (the National Space Society) based on a presentation by Curreri and Detweiler at Spaced Studies Institute Space Manufacturing Conference 2010 says the numbers are better than that.

    Please go to the NSS website and look at

    nss ==> settlement ==> journal ==> Curreri and Detweiler

    Also, SSI ==> 2010 conference – space manufacturing 14 ==>

    archives of space manufacturing 14 ==>

    Habitat Size Optimization of the O’Neill – Glaser Economic Model for Space Solar Satellite Production


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