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What is the practical limit on the dimensions of a space station built following modern technology?

What about various mechnical stresses, tensions, torsions, atmosphere drift, tide forces etc that would disintergrate the construction given currect module size and connections?

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    $\begingroup$ This is pretty broad. Since at the end of the question you mention module size, you mean using the kinds of modules in the ISS? $\endgroup$ – kim holder Apr 25 '15 at 23:17
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    $\begingroup$ The question would be more answerable if you make that clear, i'd recommend putting it in the title. The people who know enough to make the calculation give their attention to questions that are clear and specific, otherwise it isn't really worth their effort. If it doesn't seem clear from the title, they may well not read it. $\endgroup$ – kim holder Apr 25 '15 at 23:45
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    $\begingroup$ By the description of the various things mentioned, I'd see those limits would be larger than the $ limit any nation is willing to pay for a space station. So not a technical limit, but a financial one. $\endgroup$ – Andrew Thompson Apr 26 '15 at 1:08
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    $\begingroup$ "I am interested in technical limits." Then you'd be the only one. Everybody else would realize that long before you got to the technical limits of the current modules, it would call for a basic redesign of the station (e.g. to add a spinning section to provide artificial gravity for the occupants when off duty, or doing experiments that don't require microgravity). $\endgroup$ – Andrew Thompson Apr 26 '15 at 11:54
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    $\begingroup$ "That's no moon! ..." $\endgroup$ – Mark Adler Apr 26 '15 at 17:08
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The problem with this question is that the technical, financial and political limitations are interlinked.

Basically, given enough money and political will, we could probably build a space station of any size we wanted, up to something resembling a small moon, just by throwing enough money and rockets at it.

Mechanical stresses are not an issue, at least not before the station becomes big enough to have a significant gravity field of its own (which, just in case it's not obvious, would be absurdly huge) — we'd just need to build the station strong enough to withstand them. If we can build skyscrapers and giant cargo ships down here on the surface, where they have to withstand the Earth's gravity in addition to any other forces, we surely could build structures of similar (or much larger) size in orbit, if we could just get the necessary materials up there.

Sure, we'd have to increase our current launch capacity by a factor of thousands or millions to complete such a station in any reasonable timeframe, but in principle, that's perfectly doable. And that's not even considering any crazy-but-technically-possible alternative launch technologies like Project Orion that we could pull out of mothballs if we really wanted.

Of course, the big assumption here is that diverting such a huge amount of resources to space launches wouldn't collapse the economy or trigger some kind of an environmental disaster, and that some opportunistic political / ideological / religious movement wouldn't exploit the resulting hardship and dissatisfaction to take over and, as a side effect, kill the space station project. To make this work, we'd need a really good and really obvious reason for everybody to commit to such a project — something like an imminent attack by genocidal space Nazis from the moon just might be enough.

Basically, the point I'm trying to make here is that the maximum size of a space station is not limited by technology, except insofar as technology partly determines what is currently affordable.

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  • $\begingroup$ "we could probably build a space station of any size we wanted, up to something resembling a small moon," - my question is about space stations built according the current technology only. The technology used in ISS or Mir for instance. Current berthing/mating devices, current size of modules etc. $\endgroup$ – Anixx Apr 26 '15 at 15:18
  • $\begingroup$ Steel beams are current technology. So is welding. (Yes, even in space.) The only reasons why we don't build big sturdy steel frameworks to support our space stations are that 1) we don't really need to, and 2) it'd be damn expensive to ship that much steel up into orbit. But if cost is not an issue, and you only want to know what's technically possible, that's the way to go. $\endgroup$ – Ilmari Karonen Apr 26 '15 at 16:30
  • $\begingroup$ You seem to be under the impression that the structural connections currently used e.g. on the ISS would be the strongest we can currently make (or at least somewhere close to that). They're not. Rather, they're the cheapest, flimsiest and, above all, most lightweight structures we know how to make that will do the job (and leave a bit of safety and expansion margin) for the kind of station ISS is designed to be. If we wanted to make a bigger and/or tougher space station, we'd just make the connections stronger (or include additional structural supports), and just pay the extra launch costs. $\endgroup$ – Ilmari Karonen Apr 26 '15 at 16:39
  • $\begingroup$ Mechanical stresses will matter before it reaches the size of substantial self-gravitation--remember, it's orbiting the Earth, probably deep within the Roche limit. $\endgroup$ – Loren Pechtel Apr 26 '15 at 16:55
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    $\begingroup$ @Anixx: Anyway, if that's what you intended to ask, I suspect the answer is "a bit bigger than the ISS, maybe even several times bigger, but not by more than an order of magnitude." Because if the connectors and other structural elements currently used on the ISS were strong enough for a space station much bigger than the ISS was ever planned to be, somebody would've made then weaker (and thus lighter) to save on launch costs. $\endgroup$ – Ilmari Karonen Apr 26 '15 at 17:31
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While Ilmari Karonen's answer is fine I think there's a more fundamental issue here that you're missing:

We built the ISS weak not because we couldn't do better but because there was no reason to do better. Thus it is in no way an indication of what we can do.

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  • $\begingroup$ I am not asking what the limit of what we can do. I am asking what is the limit for the technology CURRENTLY USED. $\endgroup$ – Anixx Apr 26 '15 at 17:18
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    $\begingroup$ @Anixx Except the limit isn't technological. It's no harder to build things stronger, it just takes more mass. Given the price per pound to orbit they build as light as they can. $\endgroup$ – Loren Pechtel Apr 26 '15 at 19:13

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