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For the obvious reason of weight, our modern space stations and satellites are made out of metal or lightweight compounds to reduce cost. In a quick Google search, about $20,000 per kg is the cost, to be exact. This limitation greatly influences the actual construction of stations. But what if the material cost was roughly the same as it would be for building a structure on Earth itself? It's the future, we have a Space Elevator, space asteroid mining, in-situ manufacturing, you name it we have it. How would that change our station designs? Would several feet of concrete or solid sheets of lead be useful for blocking radiation, etc.? What about other materials we commonly use, like wood, or clay?

The focus here is on creating a 'good enough' station with already existing materials (2018), and examining the uses of said materials in space. Other considerations are secondary. As some pointed out, more advanced and useful materials exist, but are not being considered due to the large increase in price. They are utilized in more important works, such as military stations and the like, but for your run of the mill habitation station, it is excessive.

For the purposes of the exercise, the following holds:

  • The cost of materials is the same as what it would cost on Earth, plus some % that it took to take it into space. So cheaper materials will always be cheaper than more expensive ones.

  • The 'economy' of supply and demand is considered to be the same as well, for simplicity's sake, so metals will not end up being the dominant force in terms of cost due to asteroid mining.

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    $\begingroup$ The question is a bit broad. Perhaps specify exactly what materials you are interested in. However I would like to point out that this question doesn't make a lot of sense to me. If you are so far into the future that you have a space elevator, you should just technobabble your materials. We cannot predict what they might build materials from. We cannot even predict what kind of wood they have. If you say: Welcome to the year 4000 where space stations are made out of the same stuff we have today but we are still super advanced, your audience might be thrown off $\endgroup$ – Raditz_35 Aug 3 '18 at 20:41
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    $\begingroup$ Also clarify: what's the decision criteria? Are you asking about the "best possible" material? Or maybe you're asking about the easiest or cheapest. If anyone can build in space, I would presume that the cheapest "good enough" building materials would predominate except for e.g. military structures and spacemansions. $\endgroup$ – workerjoe Aug 3 '18 at 20:43
  • $\begingroup$ @Raditz_35 I'm curious if some of the more 'inefficient' materials like concrete would actually be useful in the construction of a space station, barring the cost. I wouldn't doubt that they have an Unobtanium material to work with by now, but the base assumption is that it is much more expensive because it is so advanced. So if we could make a station with 'good enough' cheap materials we would still do so. $\endgroup$ – Raznarok Aug 3 '18 at 20:44
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    $\begingroup$ @Joe the decision criteria is based around what you said, cheap "good enough" materials. We can obviously make a much better station, but at a much higher cost. $\endgroup$ – Raznarok Aug 3 '18 at 20:46
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    $\begingroup$ Is it your premise that all building materials have the same costs (relative to each other) in space in your world as they currently have on earth? It seems far more likely that some things would be cheaper (like iron), and others would be more expensive (like concrete, or anything else derived from limestone) $\endgroup$ – plasticinsect Aug 3 '18 at 20:55
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For all the major stuff, since you have a space elevator you don't need to worry about weight, just usefulness and cost. Here are my thoughts:

  • Lead for the exterior shell and exterior window shutters. It's cheap, durable, corrosion resistant, and it's a good insulator of radiation.
  • Steel alloys for the interior walls and essential (deck dividing) doors. We've got some good durable cheap steel alloys in the works these days. (it's a link!)
  • You don't need much more than cheap plastics for nonessential (non-safety related) doors an
  • Advanced durable ceramics (another link!), lined with electrochromatic glass, for any windows.

For hermetically sealing the craft:

  • You could run treated concrete between the lead exterior and steel interior to ensure no gaps, but if this space station is going to be very big or if it's going to have any components which vibrate a lot (like some kind of spinning futuristic motor that vibrates for some reason), then you're going to want to run with a plastic-reinforced concrete, or none at all. Concrete cracks over time, and it's not easy to repair without removing and replacing it.
  • Rubber is a good choice to seal the ship. It's cheap and it lasts a long time. Getting the right kind of rubber might be somewhat expensive, but the materials themselves are probably going to be much less costly than the tests to ensure that they were installed correctly.
  • If you want to be original, you could use wood sealed with tar and pitch. It's not very size/weight-efficient, but it's very effective for hermetically sealing a thing, and it's flexible and durable so you can put put a layer of wood between your lead exterior and steel interior, and grout the gaps with tar. The price of wood varies quite a bit, though, so getting the best kind of wood might be more money than it's worth.

I hope this helps!

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  • $\begingroup$ Some of things I wondered was, some concrete is porous, so does that mean that it can HOLD oxygen? And how well does wood hold up in a vacuum? I think at least a smattering of concrete if not more would be great due to the fireproofing it would allow. A whole station made of only metal would be weak for that reason alone. $\endgroup$ – Raznarok Aug 4 '18 at 2:21
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    $\begingroup$ concrete needs gas exchange from the air to harden, so no concrete in vacuum. It also continues to absorb gasses for years so it is a really bad idea for the inside of a space stations. $\endgroup$ – John Aug 4 '18 at 3:34
  • $\begingroup$ @John why is that exactly? Are you saying like, in terms of poisonous gasses? Or just the need for extra oxygen? $\endgroup$ – Raznarok Aug 4 '18 at 4:13
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    $\begingroup$ well outside it just won't set period, inside it will constantly drain CO2 for years, this is what actually killed biodome 2, it depletes C02 which the plants need to generate oxygen. oxygen levels drop but just adding oxygen doesn't fix it. New concrete with additive (like plastic reinforced) can release all kinds of stuff. It is also really good at corroding metal. $\endgroup$ – John Aug 4 '18 at 6:14

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