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Let's suppose I want to create a pressurized dome structure on the surface of Mars, but I want to avoid the time/effort/expense/engineering of sealing the base. Let's further stipulate that I've got a good subsurface geological survey of the area, and I've confirmed that there are no voids or caves beneath the area.

How do I engineer the seal between the dome and the surface? Does the surface need to extend subsurface? Is surface concrete plus the weight of the dome enough to seal? How do you protect against subsidence around the seal?

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    $\begingroup$ This is a good question. Generally, you can expect that any habitat will have some air loss, the question is how much is manageable and what kind of loss would you experience if it was just surface sealed via weight and concrete. I look forward to the answers. If the air loss is manageable, I would think you could just patch the concrete where it breaks due to subsidence. $\endgroup$ – called2voyage Dec 6 '16 at 21:39
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    $\begingroup$ On one hand, this seems to be a good question. On the other, and then what? Martian dirt is toxic to humans, so what is the point of sealing a habitat directly to the dirt, when the dirt will kill the humans living in it anyway? $\endgroup$ – Cody Dec 6 '16 at 23:54
  • $\begingroup$ I still think this is a great question, because it begs the larger question "How will a Mars community expand?" If our first hab is slightly sub-surface, can we dig deeper underground, perhaps covering the walls and dirt with a plastic sheet just strong enough seal to keep the dirt out, and atmosphere in? If not, it means literally every sq. ft. of living space will need to be pre-planned, packaged, and shipped to Mars, in "blow-up" hab format. They would still be dependent on care-packages from Earth, but now even more so. No self-expansion, no chance of self-sustaining colony. $\endgroup$ – IT Bear Dec 7 '16 at 1:13
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    $\begingroup$ @Cody, Well "Martian dirt is toxic" vastly overstates the case. The more accurate rendering would be "If people ate food grown in utterly untreated Martian soil for an extended period of time, many would develop thyroid problems that would require medication." So, obviously, you bioremediate that soil, through direct microbial treatment and more grossly through growing stuff like bamboo that would concentrate the percholorate (in the bamboo) and remove it from the soil. $\endgroup$ – Chris B. Behrens Dec 7 '16 at 15:29
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In an answer to another question, I suggested that a double or nested dome could be used:

Double Dome

The basic idea is that if the outer dome is a bit leaky it's not a big deal because the leakage can be continually replaced with compressed martian atmosphere using big dumb compressors. Leakage from the inner dome to the outer dome would be relatively slow due to roughly equalized pressure. In this way a measure of leakage can be actively accommodated without putting undue stress on the machines responsible for creating a breathable atmosphere.

A dome with an unsealed floor would want to behave in a manner not unlike a hovercraft, with the air wanting to rush out under the sides and also lift the dome up. So it'd be necessary to both bury the skirt and have some beefy regolith anchors - alternatively the pressure could be contained by burying the dome or making the dome incredibly thick; about 4m of regolith-concrete or 10m of ice for 0.4atm of pressure. Either way, I suspect that using a completely sealed dome and carting the regolith inside would involve much less digging.

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  • $\begingroup$ Yeah, I'd read that answer before and had it in mind when I asked this question. It's a terrific idea. $\endgroup$ – Chris B. Behrens Dec 7 '16 at 15:35
  • $\begingroup$ Anchoring wouldn't need to be maximum depth at whole circumference. Drill anchor holes, insert anchor bars - tubes with corrugation and perforation by the end; fill with binding agent (liquid glue) forming big globs of regolith bound with the anchor bar deep under the surface. This structure is not easily ripped out of the ground. Bury the skirt between the anchor points just deep enough so that leakage of air through regolith would be negligible. $\endgroup$ – SF. Dec 7 '16 at 15:49
  • $\begingroup$ Similar sealant injections would help reducing porosity (=leak potential) of the regolith along the border and keep the skirt anchored. As for pressure durability of material concerns, an onion structure was suggested - multiple nested domes of gradually increasing pressure. $\endgroup$ – SF. Dec 7 '16 at 15:58
  • $\begingroup$ @SF I think that icrecrete could have real potential as a construction and sealing material. A plastic sheet and layer of regolith should mostly eliminate sublimation problems. $\endgroup$ – Blake Walsh Dec 7 '16 at 22:55

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