I want to understand why we do not build space stations in a similar way that we build a home, piece by piece. Instead we construct modules on the ground and fly them up. Are there some technical limitations other than money that make this impossible?

Why don't we fly up raw materials, prefabbed metal panels, structural steel and any other material and slowly construct a space station that is suitable for somewhat normal living, normal sized rooms, ceiling heights, etc.?

I'm wondering if any plans exist or working groups are exploring this idea. Or is it a technical limitation, for example: not being able to ensure a complete seal between the exterior pieces?

Is what I am wondering clear?


2 Answers 2


Somebody has to put the pieces together somewhere.

If you do it in the ground, you can work in shirtsleeves, with easy access to supplies, tools, equipment, and other workers. If you need a tool, you can probably walk next door to get it, or ask someone to bring it to you. If you drop a tool, you can pick it up.

In orbit, you have to work in a bulky pressure suit, with perhaps one or two other astronauts helping, with everything you use costing thousands of dollars per kilogram and months of advance planning to get to orbit. And if you drop a tool, it can float away and be lost (and have to be tracked by NORAD).

The more assembly work you can do on the ground, the easier and cheaper the entire process is going to be, likely by several orders of magnitude.

The optimal method is to assemble things on the ground in modules as big as you can carry into orbit, and (if necessary) assemble the modules as simply as possible once you get there. This is why the International Space Station consists largely of connected modules, each of which fits in a Shuttle cargo bay. (Thanks to dmckee for pointing this out.)

  • $\begingroup$ The more assembly work you can do on the ground, the easier and cheaper the entire process is going to be modulo there being a lift platform that can orbit the finished product, of course. $\endgroup$ Jan 24, 2012 at 22:50
  • $\begingroup$ @dmckee: Good point; I've updated my answer. $\endgroup$ Jan 24, 2012 at 23:38
  • $\begingroup$ The finite size of cargo bays is also why many space structures unfold or inflate in space. $\endgroup$
    – Andrew
    Jan 25, 2012 at 11:05
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    $\begingroup$ Well, if you drop a tool, wait exactly one orbit, position yourself in the exact same place, and open hand. The tool will conveniently present itself for you to grab it. Of course, assuming it doesn't hit anything meanwhile, and you don't have to apply orbital corrections. $\endgroup$ Jan 26, 2012 at 2:02
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    $\begingroup$ @opensourcechris: Not worth it until you're going to build more than a handful of them, and that is not worth it until you have the capacity to launch more than a few. The cost of putting mass in orbit is the single biggest impediment to doing anything really interesting in space, and it is arguably the case that NASA is the single biggest impediment to bringing the cost down (not their fault, but they are at the mercy of congresscritters for funding...). $\endgroup$ Jan 28, 2012 at 19:31

The most comparable thing would be constructing a submarine, not a house. Let's bring a few things to consider.

  1. They must be air tight.
  2. They have complex electronics to regulate systems.
  3. They both operate in non-typical environments.

Submarines are typically constructed in dry docks, and then placed in the water. That way they can get everything welded when it is easy to do so, and won't have problems with constructing in an extreme environment.

  • $\begingroup$ Great example!! $\endgroup$
    – Fattie
    Dec 24, 2015 at 4:01

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