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So I’m trying to make an orbital city, kind of like the ISS, but on a much bigger scale. And against all logic and reason, I want there to be balconies. Like, where someone can just step outside, wearing normal street clothes, with nothing in between them and space, and not die. I’ve gone down the list of things that are completely implausible about this scenario, but my two main sticking points are the lack of air and pressure.

So here’s my question: if you could just have a plant that could somehow survive in space, ejecting air out into space, at a constant rate, how big of a cloud of air would be needed for space to be survivable, both in terms of pressurization and breathability. Even if only for a few minutes. I know that any air released would eventually diffuse out into the vacuum, but if it was being produced fast enough, could the conditions be constantly survivable-ish?

Some info:

  • the air is coming from a bunch of plant-type things that are growing all over the hull of the station and can survive space because reasons
  • the station is geostationary and pretty big, haven’t decided how big yet
  • most of the living and working quarters are both inside and airtight, going outside every once in a while is really just something done for aesthetic purposes.
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It wouldn't work, no matter how large the production of air, unless it is orders of magnitude larger than the size of the station!

Air will dissipate very quickly, and against vacuum will actually rush away at the speed of the molecular motion

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  • $\begingroup$ Well, that's unfortunate. Any suggestions for containment? Beyond just not having holes going out into space, of course. $\endgroup$
    – possiblySerious
    Commented Jan 16, 2016 at 3:58
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    $\begingroup$ Star Trek hangar decks use force fields. For hard science near future, a thin membrane is not enough because you also need to handle the harshness of space on the outer surface and worry about radiation. See the Cupola on the ISS for a real-world version. $\endgroup$
    – JDługosz
    Commented Jan 16, 2016 at 4:01
  • $\begingroup$ I wouldn't have to worry about radiation, because the station's orbit would still be within the planet's magnetic field. But for a thin membrane, what other specific space-harshness would I have to worry about? $\endgroup$
    – possiblySerious
    Commented Jan 16, 2016 at 4:07
  • $\begingroup$ @possiblySerious Space Junk! Little bits of metal (or rock, or tools) flying around at orbital speeds which can blow holes in Al a few inches thick... $\endgroup$
    – PipperChip
    Commented Jan 16, 2016 at 4:18
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    $\begingroup$ You still have radiation. A plastic material would find the vacuum and temperature extremes to be quite hostile. $\endgroup$
    – JDługosz
    Commented Jan 16, 2016 at 6:32
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You need enough air that its own gravity holds it together. However that means in the center you'll have much more than atmospheric pressure; indeed I don't think your air will be gaseous in the center. In other words, what you have built is not an air cloud, but an air planet (except that it might not orbit a star — but if you want to have a gaseous atmosphere, you better do orbit a star, or else the air will freeze).

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    $\begingroup$ You are probably thinking of a bubbleworld. Dani Eder calculated that a sphere of gas 240,000 km in radius, capped with a protective layer that supplied enough gravitational counter pressure to balance the pressure of the gas within would create a layer of living space with Earth like pressure and temperature near the surface with 1400 times the surface area of the Earth, and about a million times the useable living volume. See yarchive.net/space/exotic/bubbleworld.html $\endgroup$
    – Thucydides
    Commented Jan 16, 2016 at 18:25
  • $\begingroup$ @celtschk, Please, tell me more! I like where you're going with this! $\endgroup$
    – Len
    Commented Jan 18, 2018 at 20:35
  • $\begingroup$ @Thucydides, thanks. That was awesome! $\endgroup$
    – Len
    Commented Jan 18, 2018 at 20:35
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Reminds me a bit of a story where a guy makes a very small station with gravity and an atmosphere by having a very small sphere of nutronium sealed and magnetically suspended in the center. The gravity was strong enough to keep an atmosphere in and keep everyone from floating around.

In the end he self destructs the station by releasing the containment and collapsing the whole thing into the sphere.

So, you could keep the atmosphere in if you had a deep enough gravity well, however you hand wave it.
Maybe the plant makes gravity?

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If you have force-fields, then you could use these to contain the air and provide a safe atmosphere with adjustable atmospheric pressure. Then you can comfortably chill on your space balcony until a comet comes and smashes you into oblivion. You could also have many plants on these balconies to replenish the air supply.

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  • $\begingroup$ I like a little handwavium now and then and in this case I think it'd be easier to suspend disbelief. I wish someone could comment on what kind of force could actually theoretically do this (other than gravity) but sadly that someone isn't me. $\endgroup$
    – Toadfish
    Commented Jan 17, 2016 at 6:03
  • $\begingroup$ See this Question $\endgroup$
    – JDługosz
    Commented Jan 17, 2016 at 21:47
  • $\begingroup$ en.wikipedia.org/wiki/Plasma_window $\endgroup$
    – QuadmasterXLII
    Commented Nov 2, 2017 at 21:59

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