I've hit a wall in my tale of humans attempting to escape the Singularity or a fate worse than death by running off into the depths of space. And I only have myself and my accursed hard sci-fi leanings to blame.

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First of all, my habitats leak like a sieve, even before getting battered by micrometeorites, leaving my 'survivalist' fanatics gasping for air and dying faster than a gecko's libido on a Russian lizard sex satellite. Furthermore, as the poor fools stumbled around my spinning cylinders, the maths suggests that they would made them wobble so much that their tears of despair would falling sideways and my glorious cylinder-habitats (above) now have to look like ugly stumpy tires (below). But forget aesthetics, it's the air loss I'm most concerned about.

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Does anybody know of a long-term non-planetary habitat model in space that seems actually sustainable? I'm talking wall materials, docking ports, EVA ports, the occasional window (if needed, it can be windowless), etc. Would giant hollowed out space rocks fare any better? Where to put my flesh-human holdouts?

Tech level can be a tad higher than current, but should be plausible given (late) 21st century standards. Remember, these are regular unaugumented humans escaping the impending techo-singularity event on Earth, sometime in the second half of the 21st.

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    $\begingroup$ . . . How long did it take you to come up with that title? :-) $\endgroup$
    – HDE 226868
    Jan 7, 2015 at 1:52
  • $\begingroup$ Does "depths of space" mean deep space, between the stars? Or does somewhere in the solar system work? And I assume this needs to be doable with current tech? $\endgroup$ Feb 18, 2015 at 15:34
  • $\begingroup$ Near tech, anywhere from Mercury to Oort cloud. I'm assuming deep space would be off-limits, since any credible 21st tech long-term station would need volatiles resupply and a powersource, thus fuel. $\endgroup$ Feb 18, 2015 at 15:42
  • $\begingroup$ last title edit, i promise :) $\endgroup$ Feb 19, 2015 at 3:12
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    $\begingroup$ most answers are now outdated $\endgroup$
    – Vincent
    Feb 19, 2015 at 3:53

7 Answers 7


Alright. So this is a multi-stage project.

First, we head to the asteroid belt. There we alter the orbit of a ton of asteroids with useful properties (water, metals, etc) and send them off towards Venus. They don't have to be exact, or quick, we're just looking to supply ourselves over the long-term here. Think minor alterations that will put the asteroids near 10, 100, or 1,000 years from now.

Now we pick a couple of decent-sized asteroids to jump-start our project, put those on shorter orbits and head to Venus to start constructing our habitats. And now we have a two-step plan to mitigate air loss.

Self-healing water shielding

The idea here is that you have a two-layered hull, with 1-2 meters of water in between. That's enough to cut down almost entirely on radiation. But a secondary benefit for us is it also helps us keep our air supply intact by reducing leakage. Air won't go through as easily. The water also helps absorb and protect against micro-meteorites - what you do is mix some sort of replaceable fiber in with the water. Then when your outer hull is pierced, as you lose water the fibers will tend to bunch up against the hole, acting similar to how human blood cells clot to prevent bleeding. The water will alternately boil/freeze but should eventually stabilize.

We can keep it from freezing by picking an orbit that always keeps us in sunlight, and we can circulate the water by painting the outside various shades between black and white, ensuring uneven heating.

Maintenance will be tricky. Eventually enough small impacts will build up to the point where we want to entirely replace the outer hull. Probably the best way to do this would be to temporarily evacuate, drain the water shielding, replace the outer hull, then pump the water back in. We could make the outer hull out of something like fabric to make replacement easier, rather than metals - it will hold its shape due to the water pressure, so doesn't need to be a solid. Alternatively we could have all our habitats be somewhat temporary, and just replace them before the likelihood of failure gets too high.

Water shielding is a known idea, but with current tech it's not feasible to get enough water into space to make it useful. Thankfully we went to the Asteroid Belt first, since plenty of those will have some water.

Harvesting Carbon Dioxide

The fact is that there's no way with current tech to totally prevent air loss. You're always going to lose some whenever you use an air lock, and there will be some leakage no matter what. So our way around that is to replace it, and that brings us to why we're around Venus - we're going to get our air supply from it.

Obviously to keep ourselves alive, we need huge greenhouses to provide food, and eat carbon dioxide and give us that oxygen. So every once in a while we'll hop into our giant gas harvester (space ship with a big balloon attached?), go a little bit into Venus's atmosphere and fill our bag. Then we can slowly filter that into our greenhouses, where the plants will eat the CO2 and give us yummy oxygen.

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    $\begingroup$ Re Venus: Much easier to get air/water supply from Jovian moons. Just dig out chunks and launch them in the right direction with a mass driver. $\endgroup$
    – jamesqf
    Feb 18, 2015 at 19:53
  • $\begingroup$ The main reason I picked Venus was the CO2 atmosphere, and the fact that it's closer to the sun so you have more energy/easier to keep your water shielding from freezing. I was considering Jupiter first but wasn't sure where you'd get your atmosphere from. $\endgroup$ Feb 18, 2015 at 19:55

Stick yourself in a rock and hope for the best.

That's literally the best approach. It's a bit more elegant than that sentence might make you think, but it's something.

I'll tell it like a story.

You're strapped into the transfer shuttle, nervously waiting to enter your future home. You'll be sharing it with hundreds of others, but it's a home nonetheless. Making the habitat communal was the only feasible way. Putting small groups of people in smaller habitats means it's harder to get from one dwelling to the other. Smaller habitats also mean lower gravity. Although there's low gravity in the habitat you're going to, it's weaker still on smaller habitats.

You're going to an asteroid - specifically, Vesta. It's over 500 kilometers long - enough to fit have a dozen cities, and then some. However, most of it is uninhabited. At the moment, only 500 souls live on one end, though the capacity may go up to 1,500. Some of the other space is used for mining, and the center is solid. The two opposite ends are connected on the surface with a special railroad; shuttle flights between the ends are too difficult, and maneuvers are tricky. The reason the center of the asteroid is never going to be hollowed out is that the planners wanted the center of gravity to stay in the same place, so it would continue to move semi-normally.

The shuttle gets closer and closer to what seems to be a tiny opening on one end. It's a door about 20 feet high and 30 wide - barely enough for the shuttle to get in (Vesta is in the main belt; a larger ship, on its way to a mission to the outer planets, dropped you off near the belt, and a shuttle docked with it and took you to the asteroid. Specialized flights are way too expensive, even with groups the size of yours - 20.).

Now the shuttle is inside, and it's landing. As the engines power down, you walk down the boarding ramp and are greeted by a friendly man who would seem more in place at a department store as a salesman. You and your 19 companions follow him as he shows you around.

After telling you all the preliminary details that you learned before you left Earth, he gets to the details you didn't know. "We're going to go deeper into the asteroid," he says. "At the moment, we're as close to the surface as you'll be for a while." You all walk to a rather large room - which is an elevator - and descend.

The feeling is astonishing. You'd spent months in zero gravity, but now your stomach does a belly flop. After you landed, your boots became magnetically linked to the floor with each step, a vain attempt at simulating gravity. In the elevator, there are no magnets under the floor, and were it not for the railings your guide has wisely pointed out, all 19 of you might flutter around the elevator.

Your guide smirks then gets on with his information. "We're currently going over 10 kilometers down into the asteroid," he says. "Can anyone tell me why?" Nobody can - which he knew - which gives him a smug feeling of superiority. You're impatient, though, and wait for him to tell you.

"There are a few reasons," he says. "The first is to protect you all from cosmic rays. If you stood on the surface of the asteroid, you'd be hit with a lot. Sure, 10 kilometers of protection may be overkill, but the engineers needed the structure to be strong.

"A second reason is UV light. On Earth, you had the ozone layer. Here, there's nothing of the kind. Again, 10 kilometers is overkill, but there are reasons for that.

"The engineers also wanted to watch out for collisions with other asteroids. Here in the Asteroid Belt, the density of asteroids per a given volume is surprisingly low. However, collisions are possible. Vesta is one of the biggest ones - that's why it was chosen - but a hit could cause damage. 10 kilometers should be enough to protect it from anything short of a direct hit."

Finally, the guide shuts up, and you wait for the next hour to pass. It feels like you're going slower than a snail, but you're going faster than that. It feels like an eternity has passed before you reach your destination.

"Come on," the guide says. "I'll show you around." You all hurry after him, and he starts to talk. "As we pass along this corridor, we're going towards the central area. It's built like a giant bubble - just an enormous cavern carved into the asteroid. There's a twin-ish area on the opposite side for mining. However, we left some parts of the asteroid inside the cavern intact, for support. You travel along from one part to another via ziptracks."

Ziptracks? What are those? Then you enter the cavern. It's about one kilometer across - it's huge! You look around, up and down, and you see people floating about. Most are on tethers, attached to something nearby, but some are attached to small carts on ropes - carbon nanotube-based tracks, someone whispers - that traverse the cavern.

On the walls, there are people and dwellings. You think you see gardens and buildings. There's no gravity - save for some magnetic boot tracks - but it's so amazing. You could get used to this, you think.

Some credit goes to celtschk, for inspiring this format.


I kind of have to agree with Vincent's comment:

most answers are now outdated

Mine certainly is, now that the question has been edited. I'll keep the above part because I like it (shamelessly praising my own work), but I'll write up what's basically a new answer.

Protection from micrometeorites and cosmic rays

Without proper protection, your poor guys are not only going to be stumbling around but getting seriously ill from cosmic rays coming in. We're pretty shielded here on Earth, but in outer space, all bets are off. These two answers discuss the types of shielding that are used in space stations and the ISS. The most important type is the Whipple bumper, which is detailed here along with the other two main types. It uses a metal plate to slow down high-speed incoming particles, such as micrometeorites.

I now know what I didn't know back when I first wrote this answer: You don't need a whole lot of rock to stop radiation. After all, enough layers of Whipple bumpers can stop some micrometeorites, and cosmic rays can be blocked easily enough The same goes for UV radiation. I don't know how much shielding you'd need, but it sure wouldn't be a lot. I was exaggerating it in my original answer when I said 10 kilometers (and that was also for support purposes). So your space station doesn't have to have really thick walls to protect the people inside.


The best way to avoid all those nasty, complicated air filtration systems is to make your space station have a bona fide weather system. If we're going for the hollow-asteroid approach - which seems to be our best shot - it could have weather inside it. You'll need to plant plants to help the O2 be regenerated. You then run into the problem of generating enough light for them. I'd line the outside of the asteroid with solar panels, and use the electricity to light artificial lights so the plants can grow. In addition to getting oxygen, you can also harvest food.

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    $\begingroup$ The main problem with this concept is the lack of (simulated) gravity. Have you considered spinning up the asteroid? $\endgroup$
    – Tim B
    Jan 7, 2015 at 9:25
  • $\begingroup$ @TimB Absolutely. The issue is that you'd need something like Vesta quite the push to get it spinning enough for there to be a difference - and that would only provide artificial gravity in some places; if you wanted to be in area near the center, you wouldn't be pushed by the rotation to the "floor." $\endgroup$
    – HDE 226868
    Jan 7, 2015 at 23:16
  • $\begingroup$ Re editing: I've not actually changed the text of the question at all, only the title, plus answered to a comment by specifying my preferred tech level... $\endgroup$ Feb 19, 2015 at 22:07
  • $\begingroup$ @SerbanTanasa I know; I feel that my original answer didn't quite get at what you're looking for, or were looking for before. $\endgroup$
    – HDE 226868
    Feb 19, 2015 at 22:08
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    $\begingroup$ An alternative to running solar panels + artificial lights is to funnel the sunlight from outside through fiber optic tubes. $\endgroup$
    – gsk
    Feb 20, 2015 at 21:54

Run to Europa and dig in!

Set up a temporary settlement on top of the ice but immediately start drilling. If you can reach the water, great! Lower your colony ships down through the ice and turn them into submarines. The external pressure against the hull will keep the atmosphere in and you can harvest additional oxygen either from the water or from the thin atmosphere above the ice.

You might even find some water-born deuterium for the fusion reactors so your survivalists can keep the lights on and grow some food.

If you can't reach the water, get as far as you can, then bury the colony ships in the holes you've dug and then melt the ice in above you. That will give you additional insulation which may also serve to keep the atmosphere inside. Then it is just a matter of waiting till the singularity evolves some compassion so you can move back home where it's warm.

  • $\begingroup$ And so bypass space completely! Interesting angle. $\endgroup$ Feb 19, 2015 at 11:54

If you are running away from a potentially soon to be out-of-control AI complex on Earth, going to Venus or even Jupiter might not be far away enough. Since you stated 21st century technology, your habitats are not going to be perfectly sealed, so you need to be somewhere where you can refresh your air and water.

Depending on the technology level, you might have to stick to the outer Oort cloud, or if you've some serious Joules to spare, consider a cryogenic inertial escape to a nearby Brown Dwarf, just to be out of immediate range. You can use the protodisk or the frozen planets in the Brown Dwarf system to replenish your losses, and you'll need a fusion power reactor and the ability to build all the spare parts and a basic industrial infrastructure from scratch. From the safe distance of the Oort cloud or the nearby Brown Dwarf, you can assess the danger posed by the emergent AI civilization, and make a decision on whether to run even farther, stay in place or return home.

As to the air-loss, it's a trivial problem (since you can replenish losses) compared to the more difficult problems of maintaining a biosphere to feed your people, and having an all-around industrial capability with only a few thousand people on board.


Vent waste gasses from an outer shell

The easiest way to avoid losing your precious atmosphere is to lose some other gasses instead. Build your city in the form of two concentric spheres, with all of your inhabited areas in the inner sphere and all of your industry in the outer sphere. Make sure your industry releases gaseous waste, ideally waste that isn't too toxic since little bits of it will escape into your city from time to time.

Now, reduce the air pressure of your city to less than the pressure of the toxic atmosphere your factories are producing in the second sphere. Bleed off any excess waste your factories produce into space.

How does this work?

Essentially, you'll be taking advantage of the fact that gasses like to move from high pressure areas to lower pressure areas. Since your atmosphere is now surrounded by a high pressure area, if you have any small leaks in your habitable area, the result will be little bits of exhaust leaking in, rather than your air leaking out. You can patch any holes that form and scrub your atmosphere of pollutants on a regular basis (which you'll need to do anyways) to keep the exhaust from making your atmosphere toxic and your set!

The only thing you'll need to do is periodically resupply your space city with fuel. Luckily, things like hydrocarbons and ammonia are fairly easy to come by in space. Titan, for example, has more oil than Earth. So long as your industry is based partially on burning such materials, you can use the exhaust from your factories to keep your precious atmosphere from running away.

  • $\begingroup$ While I like this idea I think you'd keep the waste gases at a slightly lower pressure not higher. This will be enough to slow escapes to a crawl while minimizing the influx of pollution. $\endgroup$
    – Tim B
    Feb 20, 2015 at 9:14

First off, nice title ;)

I'd like to suggest a highly unusual mode of transportation, the Leviathan.

Gregory Benford's book, Beyond Infinity, described a potential world where life and evolution never quit, and generated spectacular creatures which coexisted in a galactic ecosystem. In this ecosystem is the Leviathan, an unimaginably massive living creature which travels the emptiness of space in search of food.

The Leviathan has a strong advantage over nearly all other forms of transit: it is alive. It flexes and adjusts and adapts to stresses. It is also intelligent (to a point where we, as a reader, are left wondering just how vastly intelligent it might be).

It just might be your ticket. You just have to wait a few billion years for it to evolve....

... or do you?


Hollowing out asteroids is a rather common idea for generating a large enclosed space in space for a large number of humans that can withstand a decent amount of pounding from space junk.

Here I asked about an asteroid being used as a Generation ship. I thought the idea would be easier than trying to build great protection around the whole thing or the need to have extremely powerful shields trying to protect you.


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