The government of Futurestan has finally decided to hear the voice of her people. It would seem that the protriotors access to malware, EMP-otovs, and weaponized angry glaring (and thermite. Lots of thermite) caused enough of a thorn in the government's side and generated enough of a presence that the government couldn't censor the media fast enough. Well, and there was that whole "the internet gaining sentience" thing. Either way the government has sat down to listen to their grievances, the biggest of which being a lack of toilets.

Yes it would seem that the expensive and expansive process of carbon harvesting from waste and an expensive and expansive population have put a huge amount of stress on restroom facilities (this is the side of overpopulation that the media won't cover). But the government of Futurestan, along with its allied nations The Democratic People's Republic of the After Times and the United States of the Far Far Away, have managed to concoct a brilliant plan. Put them in space!!!

Using dubious information obtained from the post-sentient internet (he prefers to be called Bob), they have learned that with a population density of New York (a legendary city from the before times) they could fit ~7 billion people into an area the size of the nation-state of Texas.

Ignoring the cost of such a venture (a lot) and the difficulty of accomplishing such a task (high), the governments still ignore the most basic of problems with such a venture.


The government policy on who gets to go up in the space station, known as the Space Station, isn't so much a policy as it is "let's just sort of cram people in". Doing this with 8 or 9 people would be a problem, let alone ~7 billion. As long as you look sort of healthy and signed a waiver about explosive decompression, you were in.


Assuming Space Station to be a scaled up (present day) New York inside a hermetically sealed box flying around in low Earth orbit (or whatever is a reasonable orbit so as not to interfere with cable television and the alignment of the moon), what would be the major problems faced by its citizens?


You can also assume that:

  1. food and supplies are delivered at regular intervals in a quantity that would allow everyone on the station to lead a middle class lifestyle
  2. there are enough jobs for everyone
  3. there are enough toilets
  4. this is physically possible
  5. demographic information is similar to present day NYC for all intents and purposes, there just happens to be ~7 billion people rather than 8.4 million

If you assume more things please state what you are assuming please.

  • $\begingroup$ Are the people on the station themselves responsible for keeping the space station running, or do external engineers make sure it doesn't crash and burn? $\endgroup$
    – Theik
    Jul 28, 2015 at 12:10
  • $\begingroup$ Day to day operations would most likely be taken care of by people living on the station. Whether they have enough experts on board might be an issue though. $\endgroup$
    – Jake
    Jul 28, 2015 at 12:12
  • $\begingroup$ Do they make any effort at balancing out the population and does it have to be a viable population in itself (or are we simply trying to get rid of people here, without actually murdering them)? Simply allowing everybody on could very easily result in a ratio of 20 men to 1 woman, which could also create all sorts of problems to keep in mind. $\endgroup$
    – Theik
    Jul 28, 2015 at 12:17
  • $\begingroup$ Present day NYC is 53% female and 47% male so I would go with that assumption. $\endgroup$
    – Jake
    Jul 28, 2015 at 12:20
  • 1
    $\begingroup$ @RBarryYoung Relevant xkcd: what if - Everybody out - and that's not even worrying about food / water. $\endgroup$
    – user487
    Jul 28, 2015 at 16:37

3 Answers 3



A space station of 7 billion people will need to get rid of the waste heat somehow. Vacuum is a fantastic insulator.

Let's set a lower bound on the amount of heat that will need to be removed from the Space Station for 7 billion people. An average resting adult male generates 100 watts of heat, multiply by 7 billion people and we have heat budget of 700 billion watts. Were this on earth and waste heat can simply be dumped "outside", it would take 142.1 million 1.5 ton AC units hooked up to colossal radiation panels to move that much heat and maintain a livable temperature. (The radiation panels are needed because there is no conduction or convection in space to get rid of the heat. It must be radiated away by IR radiation.) This is the minimum threshold for heat and does not include anyone who is exercising nor the waste heat generated by electronics or equipment, nor heat absorption from solar energy.

Economic Incentives

Why go up there in the first place? Access to a toilet might be a good reason but the hedonistic treadmill will soon turn that luxury into a boring feature. Providing economic incentives to stay on the Space Station will need to be devised in the form of a manufacturing and/or services economy. It's reasonable that a civilization capable of building a space habitat for 7 billion people can also manipulate the orbit of asteroids to provide raw materials for manufacturing.

Biological Disincentives

Without artificial gravity (not stated in the OP) then the inhabitant's bodies will begin to degrade fairly quickly. Long term exposure to zero gravity may eventually preclude any chance of return to earth....though maybe that's the point? Making a station that spins shouldn't be too hard in the case we have a non-malevolent government. Bah! We're putting 7 billion people in orbit. So many technological problems have been solved at this point that we can basically do whatever the hell we want.

Feeding the population

Reliance on ground based food deliveries is a recipes for disaster. A shipment will be missed. Support will probably, eventually disappear for reasons of political, economic, or ecological viability. Feeding 7 billion people takes tremendous amounts of resources. Getting that much food into orbit requires highly sophisticated techniques for production, shipping and transferal to orbit.

  • $\begingroup$ Spinning a structure the size of Texas is no small matter ... $\endgroup$ Jul 28, 2015 at 15:50
  • $\begingroup$ I'd guess that if you can build it in orbit you can spin it, but a space station simulating earth gravity needs to support roughly its own earth-weight under tension. So as long as you can build a structure the size of Texas that doesn't snap when you hang it from its mid-point then you're good to go. $\endgroup$ Jul 28, 2015 at 16:13
  • $\begingroup$ Good point though I'm not sure if it all has to be one structure or if we're allowed lots of smaller linked units which could be spun. $\endgroup$
    – Murphy
    Jul 28, 2015 at 16:21
  • 5
    $\begingroup$ @Mołot, homedepot.com/p/… A 1.5 ton AC unit doesn't weight 1.5 tons, it just provides the cooling effect of 1.5 tons of ice over 24 hours. The US (like always) is crazy with their units. en.wikipedia.org/wiki/Ton_of_refrigeration $\endgroup$
    – Green
    Sep 17, 2015 at 12:47
  • 1
    $\begingroup$ @DavidBrown That's a benefit that does not scale. You are in space so you can only get rid of more energy in two ways. - By being hotter, or by having a larger surface area. If you go the hotter route you will need to pump against the temperature gradient. If you for larger surface area you only need to pump liquid, but you need to displace that liquid further. $\endgroup$
    – Taemyr
    Sep 18, 2015 at 11:24

Heat as Green very excellently explained.

Biological but not so much: I think those issues can be solved except that food, water and waste transfer would affect...

Economics too as Green said but even more so:

What is this station producing that it can trade with the rest of the world to an extent that it could fund itself and its 7 billion people? Food, air and water for 7 billion people being lifted off the Earth every day! Surely it isn't able to grow and recycle that much; We struggle to manage that now with the entire Earth at our disposal. If it doesn't achieve parity then it is a drain on Earth and probably an enormous one. That would make it a constant worry that Earth might cut back or even cut off support. ("Sorry guys, we really do want to keep sending you food we just don't have any left to spare. We feel really terrible about it. Bob bless.")

That leads onto what I think would be the biggest existential problem:


The Space Station would be utterly at the mercy of Earth and its political trends. One stroke of a pen and all 7 billion people will be starving or suffocating within weeks. This could be a president or a union or the effects of dissident rebels.

Furthermore, the Earth's atmosphere is a very effective shield against small asteroids and cosmic rays. The Space Station won't have that luxury.

Cosmic rays might be well shielded against but that could be very expensive (and therefore economized on).

Asteroids are a different matter though: A moderately-sized (1 to 10m) asteroid moving at a few 10,000 miles per hour will likely cause enormous damage to the station - possibly killing millions. A medium-large asteroid (10 to 100m) would be like an atom bomb and might destroy it completely.

The Earth is regularly struck by small meteorites. It is likely the Space Station would be too. Such strikes would clatter the entire structure. Such ringing thuds would signal a few thousand or million people have just died. They would be regular reminders that "The Big One" could come at any moment and then they would all be dead.

People going stir crazy from these ever-present threats and the general isolation/entrapment would be a serious problem.

There's vulnerability to sabotage too (perhaps from one of these crazies or some other fanatic): Air, water, power, food, orbital stability, etc. systems could all be catastrophically compromised if someone had the will to do so (unless very clever and careful safeguards were put in place).

Earth withdrawing or scaling back its support will be the biggest threat though because I think it would be inevitable.

Some Numbers

Average mass of a person 80.7kg, x7 billion = 565 million tonnes of people

The ISS mass is 370 tonnes and can accommodate 6 people, so 61.7 tonnes per person, x7 billion = 432 billion tonnes. The whole station would have a mass of at least a tenth that: 43 billion tonnes.

(Water usage in the western world is at least 100 litres per person per day, x7 billion = 700 million tonnes of water per day. This would surely be recycled though but the machinery to recycle that much water on a daily basis would be impressive indeed.)

Average food consumption in the US: 1 tonne per year. Say a tenth of that = 0.3kg per day, x7 billion = 2 million tonnes of food per day. To deliver that by chemical rocket would be very deleterious to Earth's atmosphere.

You're building a 43 billion tonne space station and transporting 565 million tonnes of people up to it and then 2 million tonnes of food every day. A space elevator would be the only option.

But the elevator would then be a very serious single point of failure; Any malfunction in the elevator (including, Bob forbid, a breakage) could quickly spell extinction to those on board.


If the Space Station cannot achieve self-sufficiency (at least its own food) it would start to look very much like an orbiting death camp.

  • 1
    $\begingroup$ +1 for "Bob bless." Seconded on earth withdrawing it support before the Space Station can become self-sufficient from asteroid mining. $\endgroup$
    – Green
    Jul 28, 2015 at 14:28
  • $\begingroup$ If asteroid mining is an option then it's a case of Mutually Assured Destruction because it doesn't take a whole lot to push a Tunguska or bigger size asteroid on collision course with earth. "Don't want to send us food? That's fine, we'll trade you for an asteroid. Oops." $\endgroup$
    – Green
    Jul 28, 2015 at 14:30
  • $\begingroup$ @Green Perhaps asteroid mining might save them. They wouldn't be massively better placed than the Earth itself to send mining ships to the asteroid belt. If their best bet for ensuring their survival is by acquiring the means to destroy the Earth then that's a fascinating situation (a Cold War) but an unstable one with the Space Station at a huge disadvantage: both can destroy each other but Earth can destroy the Space Station much more easily and completely, the Space Station is much more dependent on the Earth. If the Space Station destroys the Earth it will starve but not vice versa. $\endgroup$
    – Avon
    Jul 28, 2015 at 14:41
  • $\begingroup$ With asteroid mining, they would have the fuel needed to move the Space Station far enough out that any threat from Earth could be countered. Once something is in orbit, it's really easy to get it into a higher orbit (though with something this size, it's going to take a long time to move). Hide behind the moon at a Lagrange Point and Earth can't do anything. Beam weapons can't reach. Nuclear missiles will take hours or days to arrive. $\endgroup$
    – Green
    Jul 28, 2015 at 14:44
  • $\begingroup$ @Green And all the while they're starving... unless Earth continued to send them food and water... under duress... all that way. It's not going to end well; the Space Station will come out worse. $\endgroup$
    – Avon
    Jul 28, 2015 at 14:51

With the technology to put 7 billion people into space, there is no particular need to cram them all into a space structure the size of Texas. Larger ones are not only safer and more pleasant for the occupants, but also have sufficient land area to grow food and have somewhat natural ecological cycles to ensure their continued operation independent of the Earth. This is important since (as pointed out) the Earth might not be a dependable supplier for these colonists, and if the population pressure on Earth is so great that everyone has run out of toilets, then the citizens and politicians on Earth might prefer to spend their resources on other things than feeding a space colony. To give you some idea, the Island Three concept of Gerald K O'Neil would be 5 miles (8.0 km) in diameter and 20 miles (32 km) long; a McKendree cylinder is designed to be 460 km (290 mi) in radius and 4600 km (2900 mi) in length, containing 13 million square kilometers (5.1 million square miles) of living space, nearly as much land area as that of Russia, while the larges conceivable structure is a Bishop Ring, 1,000 km (620 mi) in radius and 500 km (310 mi) in width, containing 3 million square kilometers (1.2 million square miles) of living space, comparable to the area of India. (data cribbed from Wikipedia)

Multiple colonies can be built from materials extracted from asteroids, as well as mined from the Moon, the various moons of the Gas Giant planets and even Mercury. Solar energy is plentiful out to the orbit of Mars, so solar mirrors and solar panels can be scaled to provide sufficient light to grow crops, enjoy life inside and generate sufficient electrical power.

Heat rejection and keeping the life support systems closed are the two main technological issues of a space colony of any size. For the most part, larger radiators provide the cooling, and since we are in an environment where delivering 7 billion people into orbit isn't an issue, keeping the life support system(s) topped up with supplies and raw material should not be an issue; asteroids are prime sources of metals, silicon and carbon compounds; the moon Europa has 3X the water as all the oceans of Earth combined, and nitrogen can be scooped from the moon Titan. If we want to have abundant spec travel (and can hand wave 3He Fusion), then fuel for millions of years of spec travel can be extracted from the atmosphere of Saturn and Uranus.

The big social issue will have to do with population. Each colony will have limits to how many people can be aboard (life support, available crop "land" and heat rejection define the limits), so colony structures might start out relatively empty. As the population naturally grows, a new structure might be started, and the existing colony becomes crowded in the mean time (fewer toilets) until the new colony is finished and the life support started, then the population of the first colony crashes as people move out to the new colony.

A secondary social issue might be the development of a clan or tribal mentality if the colony structures are designed with multiple "bubbles" or chambers to prevent any individual event from catastrophically destroying the colony or killing all aboard. "Stay safe in your bubble" might become a watch word, and people interact between bubbles via a network system of some sort. Real interaction become rare and the bubbles become more insular in nature and isolationist. Of course since each space colony is also an independent "world" of its own, there may also be balkanization between the various polities in space, which will allow Earth or the most competitive colony to divide and conquer the various "nations" in space.

Lastly, since a space colony can conceivably be designed to pack people in a compact 3D structure (without gravity, or variable gravity if there are multiple levels in the rotating structure), then social and political structures will have to be designed to allow for efficient functioning of large numbers of people in a very small space (Manhattan at noon rather than the average NYC population density). You might have a billion people in a rather small asteroid under this arrangement, rather than them spread out like nomads on the pre contact Great Plains (which would imply other, rather different social, economic and political structures).


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