Sep 30 2016

Barriers to Colonizing Space

theexpanse_galleryWe are in an interesting time in human history with regard to humans in space. We have space programs. We have been to the moon, and we have a continuous presence in low-earth orbit. But we haven’t colonized space or any other world. We are thinking about it, and some people are even planning it, but no clear program yet.

What this means is that we are probably in the period of maximal speculation. We have a lot of information about space and space travel, and some experience, but we do not yet have any experience with actual colonization.

As is often the case, much of the speculation takes the form of science fiction. The Martian was an excellent novel and book that tried to seriously explore the issue of surviving on Mars (with some concessions made for narrative purposes).

The best speculation I have seen is in the recent TV series The Expanse. This takes place a couple of hundred years in the future, when humans have colonized our solar system. There is no magic high-tech to make the problems they would encounter go away. There is no artificial gravity, transporter, warp drive, force fields, or anything similar. They get by with extrapolations of existing physics and technology.

What are the major barriers we would encounter? One is radiation. The earth protects us in a shield comprised of the earth’s magnetic field and a thick atmosphere. There is no other place in the solar system with such protection on the surface of a world.

Radiation is not an insurmountable problem – it just requires adequate shielding. This is not a problem on a base or large station. It is an issue with a space ship because shielding is likely to be heavy, and more weight means more fuel. There are possible solutions there as well, such as storing a ships water supply in the outer hull to provide extra shielding and using strong magnetic fields. For long journeys you can also dock with larger ships that act as a highly shielded ferry and only need to be accelerated up to speed once.

Food, water, and oxygen is another problem. The earth has an ecosystem and, at least theoretically, sustainable resources. We would have to recreate a smaller version of that on any colony. We would need adequate starting materials, and a carefully balanced system to recycle all waste. No new technology is needed for this, just enough energy and careful planning and monitoring. Essentially a colony would be a human closed terrarium.

Perhaps the thorniest problem of space colonization is gravity. In fact the inspiration for this post was a recent question I received from SGU listener, Chris:

Something I’ve always had my own hypotheses about, but never heard addressed, yet seems like the elephant in the room in any discussion about space colonization, is the problem on gravity. I would assume that on a planet like Mars that has .37G, there is no way a human being can properly develop from an embryo to adulthood in that kind of gravity. I would imagine there would be ALL kinds of malformities and biological complications resulting from building a body in non-Earth gravity. I would think pregnancies would miscarry, and if not, everyone would be die somewhere in early childhood. I know we are amazingly adaptive, but variations in gravity are not something that Earth biology has ever encountered or had to be prepared for.

I think Chris is essentially correct, depending on the amount of gravity we are talking about. In the case of gravity space ships would actually be easier to fix than colonies on planets or moons. You can make artificial gravity in a ship by spinning it. Think of the space station in 2001: A Space Odyssey.

Spinning can also be used for colonies inside hollowed out asteroids or small moons. In the series The Expanse, they made a colony inside the dwarf planet Ceres. Ceres was then “spun up” in order to provide about 0.3 g. This was enough for the show so that people could walk around without any special effects. However, people who were born and lived in Ceres had weak bones and could not tolerate the gravity of earth.

Spinning is probably not an option for colonies on the surface of Mars (surface gravity 0.38 g) or the Moon (0.1654 g).

What do we know about human biology in low or even micro gravity? Not much, but what we do know is very concerning.

First, adults in microgravity experience a host of health problems. Fluid shifts occur which can adversely affect the eyes. Vestibular function is impaired. Bones and muscles weaken over time, a process that can be reduced but not eliminated by a strenuous exercise program. Research done on the International Space Station (ISS) is giving us a pretty clear picture of the health effects of life in microgravity.

But what about embryonic development? The concern is that in order for cells in an embryo to divide properly, and then separate out to form the different layers that will become different parts of the developing embryo, a gravitational gradient is needed.

During space flight there have been experiments with flies, amphibians, and reptiles. They show that fertilization and development can occur, but success rate and lifespans are reduced.

Perhaps the best evidence we have in mammals was a Japanese study in 2009. The study was actually done on earth and used spinning chambers to cancel out the net direction of earth’s gravity. They found that fertilization was not a problem, but development was hampered and live births were significantly reduced in mice.

Later research in embryonic stem cells finds that heart development is affected through dysregulation of genes in simulated microgravity. Microgravity also affects cell-cell interactions.


Colonizing space is not going to be easy, but all of the known problems are likely to have plausible solutions. Gravity might be the most difficult problem to solve, however. Living in low gravity has dramatic affects on the body that can only be partially mitigated.

The prospect of a self-sustaining colony is even more challenging because there seems to be a negative effect of microgravity on embryonic development. The exact extent and long term effects of these development changes is unknown. Also, they may not be present in low (Moon or Mars) gravity, but at present we have no data.

A lot more research will need to be done, and we probably won’t know the full effects until after we actually establish colonies on the Moon and Mars. We also will need to see the extent to which humans can adapt to these non-earth environments. We actually may eventually see the development (or deliberate creation) of human subspecies adapted to different space environments.

12 responses so far

12 thoughts on “Barriers to Colonizing Space”

  1. Mr Qwerty says:

    > Spinning is probably not an option for colonies on the surface of Mars (surface gravity 0.38 g) or the Moon (0.1654 g).

    It probably wouldn’t be that hard to construct a torus-shaped building with a spinning inside layer (using maglev to support the weight or even just some low friction wheels) to add the additional 0.62g. Doesn’t have to be a whole habitat, could be just used as a gym and/or sleeping quarters or for those with medical issues or during pregnancy.
    Wouldn’t solve all issues with low gravity, but could help mitigate some of them.

  2. “The best speculation I have seen is in the recent TV series The Expanse. This takes place a couple of hundred years in the future, when humans have colonized our solar system. There is no magic high-tech to make the problems they would encounter go away. There is no artificial gravity, transporter, warp drive, force fields, or anything similar. They get by with extrapolations of existing physics and technology.”

    Yeah, about that…

    I’m not sure if it will be in next season or not but “anything similar” is coming. (It does has some support in existing theoretical physics, but then so does warp drive.) #NoFurtherSpoilers

  3. Have you ever seen the 1987 BBC2 show Star Cops?

  4. pjfry says:

    Would it be possible to wear a weight suit, at least for muscle development?

  5. CowCookie says:

    Maybe this is a dumb question, but is there any chance health care improves to such an extent that we could just treat the effects of radiation instead of trying to prevent the exposure? So, for example, the fatal cancers caused by radiation could become something like HIV is now — diseases requiring lifelong treatment but with a life expectancy approaching normal.

  6. Nobody lives out their life on Antarctica. Space is a far shittier place. I’m not optimistic at all about colonization of space by permanent inhabitants. A tour of duty, sure. I suppose a subspecies of human that can thrive in space might feel a similar dread about living permanently on earth.

  7. bachfiend says:

    We desperately need the Space Elevator to make colonisation of space economical. To reduce the cost of putting a kg of mass into even low Earth orbit down from tens of thousands of dollars to just a few dollars.

    Although the space cable would have to be at least 40,000 km long. And the space elevator would be only putting objects into geostationary orbits at a height of 40,000 km and not low orbit. And I don’t think that there’s any materials currently available, not even carbon nanotubules, which would be able to withstand the tensile strain of the weight of a 40,000 km length.

  8. BillyJoe7 says:

    Mr. Qwerty,

    “It probably wouldn’t be that hard to construct a torus-shaped building with a spinning inside layer (using maglev to support the weight or even just some low friction wheels) to add the additional 0.62g.”

    I’m thinking that should be sqrt(1 – 0.38^2)
    The floor can’t be a right angles to the surface of the planet, otherwise you’d still have the gravity of the planet pulling you down towards the planet’s surface. It would have to be an angle to the planet’s surface. Then, to generate 1g force perpendicular to the floor, the horizontal force generated by the spinning torus would have to be as indicated above.
    Unless I’m misunderstanding something.

  9. Mr Qwerty says:

    BillyJoe7, you’re absolutely right, I wondered if someone would notice 🙂

    Yep, you need 0.92g lateral to get 1g at an angle (the internal floor would be angled 67.7º from planet horizontal).

    Still, I think running a contraption like that is a lot easier to build and maintain on (or under) planet surface than in space; easier to build, easier to spread forces (structure doesn’t have to all “hang” from the center, can be on rails/wheels/maglev), easier to dampen vibrations (from people running/doing activities), easier to spin up & down (like, for servicing), etc.

    And on that note, 🙂

  10. drriley says:

    DevoutCatalyst mentioned about Antarctica, and that does make me wonder whether or not we have anything valuable/useful to gain from, perhaps, spending a few decades (and considerably money, of course) “colonizing” extreme environments here on Earth. Perhaps not so much Antarctica, as although it is certainly extreme there isn’t much similarity between there and Mars. I realize the far north of Canada has long been “colonized” to an extent, but perhaps there are valuable lessons to be learned and information/experience gained from targeted “colonization” projections in very remote regions of northern Canada, for example, hundreds or thousands of km from the nearest community. If it were a multi-phase project then perhaps in phase 2 or 3 all contact with the outside world could be cut off, including in emergencies, for a six month or one year period. People are likely going to die on Mars, in spite of all of our knowledge, efforts and technology; and if someone has to be allowed to die in an experiment here on Earth (IF it should naturally happen), then this may be a necessary allowance to gauge the full ramifications of such an event, including as it impacts the psychology of the remaining inhabitants and their ability, among other things, to carry out routine (constant, hourly, daily, etc) monitoring and tasks to avoid systems failures or catastrophic occurrences.

    My understanding is that much of the experimentation that has been done so far – such as putting people in isolation for extended periods of time – is more to gauge how well humans can tolerate the long trip TO Mars, and not so much their ability to live and perform well once there.

    Also, maybe it would be better to choose candidates for Mars colonization in a different manner: I’m assuming that, as it stands, candidates are chosen among various professions and based on their specialized areas of knowledge/expertise and THEN within those groups candidates are vetted as regards their psychology, ability to withstand long periods of isolation, ability to work well within a small team, ability to adapt to certain things. Perhaps it would be better to work backward, as it were, and find the best candidates who match the psychological profiles and adaptability criteria … THEN put those people through a specialized education/training program where they learn and develop the skills and experience that they require – each in his/her own specialized area – with sufficient opportunities for cross-training/knowledge/experience, where indicated, to enable – as best as possible – the team to continue to function even with the loss of a specialized member of their team. Among other things, if the plan is that they will never be returning to Earth then they don’t need an education that would enable them to ever work on Earth, and so there are a good many professions whereby the education/training that is normally received contains a significant amount that will never be required and/or is irrelevant to the mission. I could see, for example, even the training of a crew physician could and probably should be altered considerably from that which would normally be required if that physician was to go on and practice his/her career on Earth.

  11. Insomniac says:

    Just a comment on the technical vocabulary used : you don’t need a “gravitational gradient”, just gravity. In fact, gravity gradients are vanishingly small on the surface if the earth and they aren’t noticeable over the typical size of human embryos or even adults.

  12. Willy says:

    I recently re-watched 2001: A Space Odyssey. The one really obvious “flaw” in the portrayal of the technology was the amount of “volume” (space for human comfort) taken up by the transportation craft and living spaces; especially in the vehicle used to fly from the earth to the moon and the conference rooms, etc. in the moon habitation space.

Leave a Reply