It seems to me that the focus on colonizing other planets [edit: using closed/airtight structures] is misguided, and that building space stations with permanent populations would be easier, and would make sense to do before colonizing say mars. [edit: I am not considering terra-forming as an option in this scenario].

I know some builders prefer to build a house from scratch than work on renovations, as working around what already exists introduces another layer of complexity.

The same principle seems to apply here. Mars has a certain level of gravity, certain surface and subsurface characteristics, and chemical compisitions, which would react in various ways with the materials used in construction. There would be certain weather effecting sunlight availability etc, and you're stuck at a certain distance from the sun, and all this stuff would have to be factored into designing a livable habitat. Then you'd try it for real and find other things we haven't thought of, surely.

The void of space is the ultimate blank slate allowing a top-to-tail system to be designed for maximum work-ability and nothing else.

There's also the gravity disadvantage. Everytime you needed something from earth, or you would have to use resources to manage a landing, retrieve the craft, and possibly return it to earth. And that's assuming one way traffic... and why is earth supporting this large scale colony that doesn't send anything back? If we mirror the history of exploration and colonization on earth we would expect space colonization to be focused on mining and so on (I imagine space based manufacturing would also make sense, since it would be cheaper to land a finished bicycle on earth than all the ores and other inputs).

A space station could receive and dispatch craft using a fraction of the energy cost that a mars based colony could. And it would have easier access to asteroids and so on (which seem to be the most easily exploited source of mineral wealth in the solar system.

People have said previously that the energy cost of maintaining an orbit would be the problem, but it seems to me that's probably a more manageable and predictable form of entropy than the ones that would be encountered on a planetary surface.

EDIT: I agree this question has already been asked, or at least answered, here: What off-Earth colony would be easiest to build?

I do no think, though, that it is a duplicate of this: Why terraform at all? as I am considering a period before terraforming has been successfully achieved.

  • $\begingroup$ Why would anyone choose to live permanently in a space station? It'd be like choosing to spend your life in prison. $\endgroup$
    – jamesqf
    Commented Apr 25, 2018 at 3:41
  • $\begingroup$ @jamesqf : not of they were big enough to have public gardens, parks & leisure environments, it all depends on the size of these stations. $\endgroup$
    – Pelinore
    Commented Apr 25, 2018 at 7:14
  • $\begingroup$ I'm pretty sure it was already asked on this site. I'll search for it when I'll have a bit more time. $\endgroup$
    – Mołot
    Commented Apr 25, 2018 at 10:49
  • $\begingroup$ @Pelinore no matter how big your space station, a planet will always be bigger. $\endgroup$
    – RonJohn
    Commented Apr 25, 2018 at 13:22
  • $\begingroup$ @RonJohn : "a planet will always be bigger" maybe actually look at the comment I'm commenting on & take what I said in it's proper context, & if you'd looked at my reply anyone could see I'm well aware of that anyway. $\endgroup$
    – Pelinore
    Commented Apr 25, 2018 at 15:04

4 Answers 4


That's a fantastic question and I think that the answer will determine the future of humanity in space.


Pro: Produces an environment we know we can live in comfortably and indefinitely even if civilization falls. Who doesn't love a new Earth-like planet?

Con: Really expensive and really slow. You have to terraform a whole planet before you get any return on your investment. Probably have to go interstellar, as we only have one marginal candidate (Mars) in the Solar System. Requires a huge investment in technology and hardware. (Bio-based processes will be part of the armamentum, but it's hard to see how that could be enough on its own in all but the most special cases.)

Living in Space

Pro: Cheap and easy to get started -- you can start small and build up. You can do it right here in the Solar System. There's lots of material to work with available in space, and lots of energy also.

Con: It seems to be very fragile -- you need an indefinite commitment to maintaining the habitat and a permanent technological society. Either lack of gravity is an unsolved problem or centrifugal gravity adds to the engineering challenges. It's not clear people would thrive in a purely artificial environment.

  • $\begingroup$ I ran through some numbers for terraforming an Earth-sized planet without oxygen in the atmosphere - worldbuilding.stackexchange.com/a/101582/6781. One thing I found is that it would take around 2500 years to get enough oxygen if you could immediately transplant as many trees there as there are on Earth (of course, that is if you're only relying on trees, but it gives you the idea of how hard it is). You might want to give a little bit more emphasis to how expensive and slow it is. $\endgroup$
    – Rob Watts
    Commented Apr 25, 2018 at 2:40
  • $\begingroup$ @RobWatts, but terraforming needn't rely on natural processes. Find yourself some asteroids with frozen oxygen or frozen water and you'll boost the oxygenation process considerably. $\endgroup$
    – JBH
    Commented Apr 25, 2018 at 3:42
  • 1
    $\begingroup$ Let me add to your answer. A terraformed planet can sustain any growth pattern up to billions of people without additional infrastructure cost. Living space can only expand so long as you have accessible resources, will never hold the numbers a planet can hold, and becomes more fragile as you grow (problems have a greater potential for catastrophe as living space is expanded). $\endgroup$
    – JBH
    Commented Apr 25, 2018 at 3:43
  • $\begingroup$ @JBH again, it's mostly to give people an idea of the scale of the challenge $\endgroup$
    – Rob Watts
    Commented Apr 25, 2018 at 4:04
  • $\begingroup$ The problem with the frozen asteroids if that they include a lot of stuff other that water: CO<sub>2</sub> and CO at the 10% level, and NH<sub>4</sub> at the 1% level and lots more things at lower concentrations. Useful, but not without creating a new set of problems. $\endgroup$
    – Mark Olson
    Commented Apr 25, 2018 at 11:09

All the resources, all the materials, everything you need to build a space station in the first place are basically at the bottom of a gravity well (i.e. on planets).

Was that "asteroid belt" I heard you say? it's a damn long way out from the sun to that, & energy to run your station out there is going to be thin on the ground as a result, travelling out & back with the ore will take a damn long time & likely even more energy than lifting the stuff off planet.

So everything you need to build, extend & maintain it has to be hauled uphill (or a very long way).

In the short term there may be advantages to a space station but ultimately in the long term the cost benefits of hauling all that stuff off world every-time you have enough population increase to need to expand (or build a new station) means that long term the planet route will win every time.

Whatever advantage space stations do or don't have long term it's just cheaper & more economic to drop your population at the bottom of that hill where everything they need (for expansion) is anyway.

Which doesn't mean we shouldn't have space stations, we should, there are a lot of things we can do with them we can't do (or can't do as easily, or as well) on a planet & they're going to be a useful part of our toolkit, but as a housing solution for the bulk of the human race they're a non-starter.

All in all even an un-terraformed planet where you have to live in a contained environment is a better solution for a growing population than a space station, at least everything needed to build new living space is close at hand there.

  • $\begingroup$ "travelling out & back with the ore will take a damn long time & likely even more energy than lifting the stuff off planet." - really? $\endgroup$
    – Austin
    Commented Apr 29, 2018 at 2:14
  • $\begingroup$ @Austin : really, depending on how fast you want to do the trip there & back of course, if you want it done in any reasonable time frame rather than years per trip (each way) then yes I really think it may be, but I don't claim to have done the math on that (you'd have to provide the time parameters for a start, until you do that can only be opinion based), feel free to do it yourself to prove or disprove my instinct there :) $\endgroup$
    – Pelinore
    Commented Apr 30, 2018 at 17:28

Planets provide lots of free stuff. Once you have your breathable atmosphere and human-friendly climate and weather sorted out, then things like oxygen and water and how to recycle the corpse of dear old Uncle Fred just sorts itself out. You no longer have to employ technicians, engineers, systems analysts to keep this all running.

Planets provide opportunities to get away from other people. Planets are big. There is plenty of space to "get away from it all". That might be a walk in the countryside now and then or deciding to become a lifelong hermit. Public parks are a poor second - and the day you want a peaceful lonesome walk might be the day 500 other people decided the same thing, or the day the local brass band society decided to hold its annual competition.

Planets provide more opportunities to make money (as an individual). Some things as equally likely anywhere (writing a best-selling novel or starting a fashion for glitter in your hair, for instance). but because planets are made of all sorts of'stuff' there are more chances to think of a 'stuff' based way to make a living. No-one on a space station can come up with the idea of and then actually sell healing crystals, pet parrots, shantoosh wool scarves, slate table mats, zebra skin coats, marble bathrooms and so on. Not to mention sports cars, hang gliders, mountain bikes, racehorses or anything else which requires lots of outdoor space to use in a interesting or fulfilling way.

Space stations are very small closed systems. Space stations - even very large ones - have limited resources. There will be an absolute maximum number of people they can feed and house. An average UK person eats 2kg of food a day, for instance, so the space station agriculture/food vats must be able to produce that day in, day out. The sewage systems have to get all the pee and poo recycled pronto or both the drinking water and the fertiliser will run short - there is no rain or eroding rocks to provide more for free. There will be reserve capacity built into the systems for emergencies, but a closed system like this may impose many restrictions on what people can or can't do. For instance, if your station can support a maximum population of 100,000 people and you want to have a kid, you may not be permitted to because the station is 'full'. You'll have to wait until one of the pensioners drops dead of old age.


planets are big At urban density you could pack the entire population of earth in Kansas. planets get you a lot of living area with lots of room to spread out and build specialized areas. building enough space stations to support that population would likely exceed the gross production of the entire human civilization.

Planets are self regulating. Planets use the least labor intensive way to regulate temprature, humidity, oxygen levels, ect. It largely cleans its own water and produce their own soil continuously. A people on a planet can survive a technological crash, people on a station would not,plague, war, civil unrest can take out a station, not just poele the station itself. Planets have built in radiation and meteorite shields, also a meteorite cannot depressurize planet.

Planets have dirt and rain. this sounds minor but you can grow food on earth literally by throwing seeds at the ground, this is again armageddon proofing your species habitat.

Biodiversity. This is really long term but incredibly powerful. planets have so many habitats and so much space you can leave a lot of it fallow for new things to evolve in, new plants or microbes that can be used for drugs or food, or technology(PCR was invented using products from hot spring bacteria), or just decoration, new animals to eat or harvest, or milk, or keep as pets. New will be a valuable resource in such an advanced society. most importantly it i can allow a place for new intelligent species to evolve, and company will also be very attractive idea to any advanced civilization. This also means planets can be sources of material almost impossibly to produce on a space station, like wood or tuna.

In truth it is not an either or, you do both each has its advantages and weakness, and the more options you poele have the more they can make, the more they can invent, and the less change the unforeseen will wipe them out.


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