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So we all know that there are lots of engineering processes that are made 100 times better by negligible gravity, and that certain engineering process need to be performed in a vacuum (electron beam welding comes to mind for some reason).

However, are there any processes that require an atmosphere, or at least significantly benefit from one? I'm only talking about vacuum v non-vacuum here, so micro-gravity is fine. Also I'm really only interested in processes the specifically relate to satellite/space vehicle construction. This is a pretty general question (which is bad I know! :/) so I'll try and pin it down a little more:

What processes are required to produce satellites/space vehicles that would directly benefit from a low gravity/microgravity environment but are significantly hindered by a vacuum?

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    $\begingroup$ Not impacted by microgravity but something to be aware of in a vacuum envonment is en.wikipedia.org/wiki/Cold_welding : "two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum" $\endgroup$ – 1337joe Jun 25 '15 at 6:31
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Applying adhesives or laying up composite materials such as carbon fibre could both be tricky. I suspect outgassing/boiling of the liquid compounds would occur causing separation in both cases.

These manufacturing processes don't depend on low gravity, unless you're working on huge structures. But the hindrance of vacuum seems clear to me.

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Anything that involves liquids, is easier with an atmosphere. What are some of these items?

  • Lubricant on reaction wheels, and other joints.
  • Glass making.
  • Applying films on surfaces like lenses
  • Working with certain types of materials

Of these, the most significant one is probably applying films on lenses. Lenses in general could be made much better in space than on Earth, but the difficulty in applying films would make it tricky. Ironically, many of these films are applied in vacuum chambers on Earth, so in theory, the same thing could be done by creating a sufficiently large sealed chamber with a vacuum in both ends.

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    $\begingroup$ Grinding and polishing of lenses may be difficult without water. $\endgroup$ – Uwe Jul 19 at 13:35
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Without a proper cooling solution, many mechanical processes build up heat quickly. Lathe and mill operations often utilize flood cooling by dumping a liquid on the part or on the tool to prevent them from melting or loosing structural integrity. To a lesser degree, the atmosphere is also often used to remove heat from parts. In a vacuum, the manufacturing process would need a way to cool the parts and tools. Finding a liquid coolant that wouldn't immediately boil away or freeze would be difficulty. Additionally, you'd want to recapture any spilled coolant somehow.

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Many common chemical reactions require an atmosphere to function.

Gasoline combustion, for example: 2C8H18 + 25O2 ~> 16CO2 + 18H2O

Without atmospheric oxygen, a car would need stored oxidizer.

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    $\begingroup$ Sandstar, the question is about satellite/space vehicle related processes (in the title). I've yet to see a craft that operates in vacuum of space and uses internal combustion engine. ;) $\endgroup$ – TildalWave Jun 26 '15 at 2:22
  • $\begingroup$ But rocket engines using petroleum and liquid oxygen work in vacuum too. $\endgroup$ – Uwe Mar 24 '18 at 20:55

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