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Assuming the recently discovered lava tube is exactly what scientists think it might be, and assuming you could build 2 walls and a door inside the lava tube, and assuming you filled it with a breathable atmosphere...

How livable would such a place be?

  • Would people need to wear protective clothing?
  • Would the air pressure blow the roof off?
  • Would the natural gravity be high enough to support life?
  • Would the enclosure retain the right amount of heat to sustain a livable temperature?

Etc. (These are sample questions, not necessarily relevant to the answer)

In general, would the lunar lava tube, with nothing more than 2 new walls, and a breathable air pressure be able to sustain a livable environment?

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    $\begingroup$ @Matthew the question is a bit non-standard for SE, but it's compelling and timely, and in this case there's a good chance this has been thought through somewhere already and may have a well-sourced answer. Let's give it some time and see what happens. $\endgroup$
    – uhoh
    Oct 20, 2017 at 4:57
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    $\begingroup$ mmm, ... our ancestors were cave dwellers & there's potential that the first representatives of humans living on celestial bodies will also be cave dwellers. History potentially repeating itself. $\endgroup$
    – Fred
    Oct 20, 2017 at 11:10
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    $\begingroup$ The lunar lava tube should be able to withstand and hold the pressure of the air. "The new walls" have to hold very large strain due to pressure and should be inserted into the tube airtight. An airlock is necessary too, simply a door would not suffice. Electrical energy should be available for use inside the habitat. $\endgroup$
    – Uwe
    Oct 20, 2017 at 15:15
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    $\begingroup$ Such a lava tube has been there a long time. You really think no meteor impact since hasn't put a crack in it somewhere? It might be structurally useful but I can't imagine it would be airtight. $\endgroup$ Oct 21, 2017 at 23:15
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    $\begingroup$ There's a relevant Engineering SE answer engineering.stackexchange.com/questions/2210/… $\endgroup$
    – Erin Anne
    Oct 24, 2017 at 2:58

2 Answers 2

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It could be, assuming it is in fact sealed. But the likelihood of it being completely sealed are unlikely. There are a couple of workarounds to such habitats that I have seen:

  1. Use some kind of an inflatable habitat inside of the lava tube - this would offer protection against radiation, thermal regularity, etc.
  2. Seal the walls somehow. There are a few ways that this could be done. One could imagine spraying some kind of a solution on the entire exposed walls, or melting the surface, or something like that to give it some kind of seal.

Personally, I can't imagine humans being in such a surface without at least 2 layers of protection against atmospheric loss. The structure of the cave will probably be shored up via some kind of coating, followed by at least one interior bubble, and possibly a second one. The cave would need to be made sturdy enough where it wouldn't fall, and to have any sharp pieces dulled down some.

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  • $\begingroup$ Spraying a solution in a vacuum might be difficult, using water as solvent impossible. $\endgroup$
    – Uwe
    Jan 12, 2018 at 17:22
  • $\begingroup$ I don't know enough about material science to know for sure, but it likely would be tricky. I suspect patching the known hole, using gas puffs to find incrementally smaller ones, and spraying something once you can maintain enough air pressure. $\endgroup$
    – PearsonArtPhoto
    Jan 12, 2018 at 17:55
  • $\begingroup$ @PearsonArtPhoto I suspect you could do it by first coating the walls to address most of the leaks and then spraying something that would set up quickly while pumping some sort of gas into the tube. The leaks would draw the material in and it would set up, sealing them. Might want to do it robotically as the likely pressurizing gas is oxygen (a sufficiently hot solar furnace applied to regolith will produce all you want.) $\endgroup$ Jan 13, 2018 at 4:59
  • $\begingroup$ In vacuum, you'd probably use vapor deposition to coat the walls. en.wikipedia.org/wiki/Chemical_vapor_deposition $\endgroup$ Oct 5, 2021 at 14:32
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Not very livable at all. Lava tubes are naturally pretty airtight in their formation but one on the moon would more than likely be pretty soft and would be more lava-stone-like, which could lead to a cave-in. The lava tube would be massive having been formed on the moon, meaning more space to carry out experiments and manufacture. You would want to have a protective wrapper filled with some kind of sealant in the event of leaks, an inner enclosure for keeping the humans away from the sealant and the hostile environment. you would hope that there is enough rock above you to block out the radiation (About three meters to be safe). you would also need all the amenities of a spacecraft such as CO2 scrubbers and water purifiers. The benefit of all of your hard work would be a space station built in a fraction of the time and for a fraction of the budget of the I.S.S.

Even with all of these precautions you still wouldn't want to keep astronauts up there for more than a year due to the lack of gravity. Most experiments being conducted would not be useful to us because of the moon's microgravity which can be achieved vs zero gravity which is much harder to replicate on Earth.

However, It would be cool to run your bare hands across the walls of a Lunar lava tube.

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  • $\begingroup$ Very interesting answer! It's always better if Stack Exchange answers refer to citations or links to sources for the facts on which they are based. Is it possible to link to some supporting sources where this information can be found? Thanks! $\endgroup$
    – uhoh
    Oct 5, 2021 at 11:46
  • $\begingroup$ Not sure what cost saving you see in building on the moon $\endgroup$
    – Antzi
    Oct 5, 2021 at 14:16
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    $\begingroup$ "Even with all of these precautions you still wouldn't want to keep astronauts up there for more than a year due to the lack of gravity." Do you have a reference to back up this assertion, that living in lunar gravity causes issues in a year? $\endgroup$ Oct 6, 2021 at 1:41
  • $\begingroup$ I find the statement "one on the moon would more than likely be pretty soft and would be more lava-stone-like" interesting. How do you know it is soft. Lunar lava tubes occur in basalt, which is a hard & competent rock. On Earth, basalt has been used as a building stone & as a foundation material for roads & as an aggregate adhered to bitumen to surface roads. What would make basalt on the Moon "soft"? Unlike Earth, the Moon does not experience weathering. $\endgroup$
    – Fred
    Oct 6, 2021 at 5:10
  • $\begingroup$ @Fred The same types of minerals we'd see on Earth are often less dense on the Moon, and Mars, due to their lower gravity affecting formation. It is a bit more complicated, because while feldspathic minerals are often lightweight and porous on the Moon, lunar basalts are actually more dense than terrestrial ones thanks to their higher iron and titanium content. $\endgroup$ Nov 5, 2021 at 18:43

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