Liquid Lunar Dust

[jee_c2]

First words: lunar dust is not liquid of course, but it could* behave like a dense liquid. That's why the title. And that can lead us to some useful applications.

Basic idea: if we apply vibrations on the lunar dust, it could behave like a dense fluid. This is an assumption (*), which could be false. In that case, the following thoughts are worthless, or they still bring some value, but with a more difficult setup.

Origin of the idea: I thought about the lunar dust, and how much difficulty it causes (and probably will cause), and tried to find something, which can be an advantage for us on the Moon. Probably I subconsciously recalled this novel of master Arthur C. Clarke, "A Fall of Moondust" (https://en.wikipedia.org/wiki/A_Fall_of_Moondust) and then came the idea of using the dust, when it is "liquified" the similar way, as the sand acts like fluid on Earth, when exposed to vibrations.

Possible application: applying vibrations, digging into moon dust is easier, so it could be possible to place an inflatable habitat in a proper depth (with proper orientation) under the surface, then also applying vibrations inflate it (the inflation could also be intermittent, vibrating). This could cause the mass of the dust over the inflatable habitat to give space (flowing) of the needed volume, so, allowing it to reach it's final size. As a result we can get a habitat, which is covered a certain amount of lunar dust, which should add some radiation and heat protection to the interior space. The habitat must have an entrance "tower" (staircase tunnel) that leads to the surface.

Possible application 2: whenever we want to process the lunar dust (i.e. to extract some materials from it, or to produce "lunar brick" from it, or just to transfer it to other place), applying vibrations to it could reduce the energy need to work with it.

What if it does not work and why could that be: the lunar dust grains are not like the sand on Earth. Because Earth has weather, and living things, the sand grains on Earth are rounded (more or less), and that makes it easier to roll on each other, so behave more like liquid. Comparing to that lunar dust grains are harsh not rounded, irregular forms, so they could attach with greater strength to each other. So the vibrations could have less similar effect, than on the Earth sand.

Workaround, helping the liquefaction, if needed: may be, releasing some gases into the dust, it can help with the vibrations he dust to act like a dense fluid.

Conclusion: this idea is based on an assumption, and that has to be checked. For that we need actual lunar dust, and also the lunar gravity can be a key parameter in the process.. which means it can be tried on the Moon. Perhaps we can conduct some experiments here on Earth with the same method, and have conclusions from the results.

I had this idea, and I'm interested in your opinions, if it had some value or not.
_{Should we "shake the Moon"?}

[Wicky]

Assuming there's not hardened soil / bedrock immediately below the surface:



I remembered first that liquid with gas bubbles in it becomes less dense - same with sand when gas is pumped into it.





Apparently the medium can't be too coarse.

[jee_c2]

Assuming there's not hardened soil / bedrock immediately below the surface:

Exactly. There are big regions on the Moon, where the dust is deep enough.
"... The thickness of the regolith varies from about 5 m on mare surfaces to about 10 m on highland surfaces. ..."
https://curator.jsc.nasa.gov/lunar/letss/regolith.pdf

 Still, it could turn out, that deeper regions of the dust becomes too dense, too much hardened.

Early days, there were also concerns about the lunar dust, as a potential problem, if it is too loose to hold the vehicles, people on it's surface (and they would sink in it):
https://space.stackexchange.com/questions/10598/is-there-any-evidence-that-nasa-was-worried-about-deep-lunar-dust

I remembered first that liquid with gas bubbles in it becomes less dense - same with sand when gas is pumped into it.

Apparently the medium can't be too coarse.

Yes. I thought, pumping some gas (ISRU based) should be only a workaround, if the needed level of liquefaction cannot be done only by applying physical effects, by applying vibrations.

More link, the Lunar dust wiki page: https://en.wikipedia.org/wiki/Lunar_soil.

[RotoSequence]

If you're going for a vibration-buried lunar habitat, you might want to go with something ceramic rather than an inflatable; Lunar regolith is composed of razor sharp micro-shards of glass, and it was doing a heck of a job eating through the Apollo astronaut's kevlar suits. A very hard outer surface should theoretically provide some sacrificial protection against the cutting action of the particulates.

[Hog]

If you're going for a vibration-buried lunar habitat, you might want to go with something ceramic rather than an inflatable; Lunar regolith is composed of razor sharp micro-shards of glass, and it was doing a heck of a job eating through the Apollo astronaut's kevlar suits. A very hard outer surface should theoretically provide some sacrificial protection against the cutting action of the particulates.

Very similar to the way Borax "attacks" the exoskeleton of certain insects.

[jee_c2]

If you're going for a vibration-buried lunar habitat, you might want to go with something ceramic rather than an inflatable; Lunar regolith is composed of razor sharp micro-shards of glass, and it was doing a heck of a job eating through the Apollo astronaut's kevlar suits. A very hard outer surface should theoretically provide some sacrificial protection against the cutting action of the particulates.

Yes, that's unfortunately right (thanks for pointing out), and it is really a problem to be solved in the proposed method for a buried inflatable habitat.
Inflatable has some advantages, that makes it something worth to fight for:
- despite the simple (which could become not so simple, because of the problem described) design and structure of the inflatable habitat, the regolith layer on the top of it would provide the needed protection (heat, radiation),
- actual building process is quite simple compared to a more robust structure (note: perhaps a 3D printed house from regolith based "ink")
- relatively small energy need for the setup, installation of the habitat.
I can imagine a shifting ceramic plates covered inflatable structure, but it could be too problematic, compared to the   advantages listed..

If we just want to bury something into the regolith (could be a habitat module), the shaking the regolith and sinking the body cold still work.. A more conservative method. For that, it's average density must be above the regoltih's (1.5-2 g/cm³). I plan to upload some illustrating drawings for these, how I imagine these.

[Mr. Tucker]

If you want to know more on lunar dust and the differences between the real thing and erath analogues:
https://twitter.com/DrPhiltill/status/1216949706154221569

[jee_c2]

If you want to know more on lunar dust and the differences between the real thing and erath analogues:
https://twitter.com/DrPhiltill/status/1216949706154221569

Thank you, a lot of interesting facts about the lunar dust. I wonder, if perhaps Dr. Phil Metzger, who seems like a specialist in the topic of lunar dust, knows about the reaction of the lunar dust to vibrations. How it behaves, when exposed to shaking. In the detailed description, he mentioned the strange behavior of the dust. the Reynolds Dilatency. As he wrote, the tendency of the dust to re-fluff when rubbed. And that could cause the wheels to get stuck (to sink, as I saw on the pictures).

[Wicky]

Recommend you read up on Ralph Bagnold a prewar desert explorer, and founder of the wartime LRDG (Long Range Desert Group) who's work is used by NASA for Mars > 'Bagnold number'

https://en.wikipedia.org/wiki/Bagnold_number

[KelvinZero]

If you're going for a vibration-buried lunar habitat, you might want to go with something ceramic rather than an inflatable; Lunar regolith is composed of razor sharp micro-shards of glass, and it was doing a heck of a job eating through the Apollo astronaut's kevlar suits. A very hard outer surface should theoretically provide some sacrificial protection against the cutting action of the particulates.

It might behave very differently from sand. I had actually wondered if vibration could cause it to settle into tightly interlocking structures.

I just googled some pictures of "sand magnified" and they looked like rounded pebbles, whereas "moon dust magnified" showed me images of things that look sort of like scoria.

[Twark_Main]

If you're going for a vibration-buried lunar habitat, you might want to go with something ceramic rather than an inflatable; Lunar regolith is composed of razor sharp micro-shards of glass, and it was doing a heck of a job eating through the Apollo astronaut's kevlar suits. A very hard outer surface should theoretically provide some sacrificial protection against the cutting action of the particulates.

Very similar to the way Borax "attacks" the exoskeleton of certain insects.

Quibble, but I think you mean diatomaceous earth, not borax. Borax just works like a regular poison.

TransHab and Bigelow inflatables have an outer cover to protect the kevlar and MMOD layers from thermal and AO, so clearly that would have to be re-designed to add an anti-abrasion layer. The inner anti-abrasion layer was made of Nomex.

[Vahe231991]

Pesky lunar dust is an annoying obstacle for astronauts landing on the Moon—it sticks to pretty much everything. New research from Washington State University may have cracked the code for keeping space suits dust-free, in which pressurized liquid nitrogen was used to literally blow the dust from surfaces.

During testing, the research team found that a sprayer full of liquid nitrogen could remove an average 98% of the dust stuck to fabric when used in a vacuum to simulate an airlock. The spray resulted in minimal damage to the spacesuits worn by simulated astronauts—Barbie dolls in Moon suits—as a result of the treatment. The research was published last month in Acta Astronautica.

At the same time, the team found that over the course the 233 total cycles of treatments on 26 spacesuit samples, the liquid nitrogen spray resulted in little degradation to the spacesuit fabric. To simulate lunar dust, the researcher used volcanic ash from Mount St. Helens, and also materials from Offplanet Research and Exolith Labs.

Lunar dust “degrades human health and equipment making mitigation paramount for lunar missions,” the scientists wrote in their study. “Cryogenic liquid sprays are a recently developed, simple, and convenient concept for dust mitigation in a lunar environment.”

https://gizmodo.com/liquid-nitrogen-moon-suits-free-lunar-dust-1850172542 [March 1, 2023]

If cryogenic liquid sprays are used on crewed Artemis missions, then they could turn lunar dust particles into some sort of liquid if any lunar dust gets on the astronauts' spacesuits.