Pressurised Natural Caves Could Offer a Home From Home On the Moon (livemint.com) 93
Long-time Slashdot reader SpzToid quotes an intriguing new article from the Economist:
Imagine a habitable colony on Mars or the Moon and the kinds of structures that come to mind are probably gleaming domes or shiny metallic tubes snaking over the surface. But with no Earth-like atmosphere or magnetic field to repel solar radiation and micrometeorites, space colonists would probably need to pile metres-thick rocks and geological rubble onto the roofs of such off-world settlements. More like a hobbit hole than Moonbase Alpha.
There could be another solution, however, that would offer future colonists safer and far more expansive living space than any cramped base built on the surface. Writing in Acta Astronautica, Raymond Martin, an engineer at Blue Origin, a rocket company, and Haym Benaroya, an aerospace engineer at Rutgers University, explore the benefits of setting up a Moon base inside giant geological tunnels that lie just below the lunar surface.
First discovered during the Apollo programme, these lunar lava tubes are a legacy of when Earth's nearest celestial neighbour was geologically hyperactive, with streams of boiling basaltic magma bursting from the interior to flow across the Moon's surface as lava. Found on Earth (see picture), and identified on Mars, lava tubes form when the sluggish top layer of a lava stream slows and cools, forming a thick and rocky lid that is left behind when the rest of the lava underneath eventually drains away.
Lava tubes on Earth are usually up to 15 metres wide and can run for several kilometres. But the reduced gravity on the Moon makes them hundreds of times bigger, creating colossal cave systems that are up to a kilometre across and hundreds of kilometres long.
There could be another solution, however, that would offer future colonists safer and far more expansive living space than any cramped base built on the surface. Writing in Acta Astronautica, Raymond Martin, an engineer at Blue Origin, a rocket company, and Haym Benaroya, an aerospace engineer at Rutgers University, explore the benefits of setting up a Moon base inside giant geological tunnels that lie just below the lunar surface.
First discovered during the Apollo programme, these lunar lava tubes are a legacy of when Earth's nearest celestial neighbour was geologically hyperactive, with streams of boiling basaltic magma bursting from the interior to flow across the Moon's surface as lava. Found on Earth (see picture), and identified on Mars, lava tubes form when the sluggish top layer of a lava stream slows and cools, forming a thick and rocky lid that is left behind when the rest of the lava underneath eventually drains away.
Lava tubes on Earth are usually up to 15 metres wide and can run for several kilometres. But the reduced gravity on the Moon makes them hundreds of times bigger, creating colossal cave systems that are up to a kilometre across and hundreds of kilometres long.
Dust (Score:5, Informative)
https://www.esa.int/Science_Ex... [esa.int]
Re:Dust (Score:4, Funny)
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Astronauts refused to carry the Moonba on the mission, citing automatic uploading of personal images.
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If the lava tubes are up to a kilometer in diameter and several kilometers in length, I think we would be setting up self-contained structures in the lava tubes, not trying to seal off a portion of them. No need for a Swiffer.
Trying to seal off a portion of the largest tubes would be like trying to put a roof on the Grand Canyon.
Re: Dust (Score:1)
Re: Dust (Score:2)
Right, because it's just like house dust, not a seriously nasty crystalline dust that can wreck the lungs in a similar way to silicosis.
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Isn't Moon dust a serious problem?
Why do you think they're pushing for more female astronauts?
--
const int one = 65536; (Silvermoon, Texture.cs)
Woke, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
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Moon dust is generated by exposure to radiation from the sun over the eons breaking down rocks, and is very shallow. It won't exist in caves, except for what the astronauts track back in with them from surface walks, which any moon mission has to deal with.
Re:Dust (Score:5, Informative)
The large majority of lunar dust (85~90%, upwards ; it's probably a bit variable from place to place depending on country rock grain size) is solidified droplets and splashes of impact glass generated by the impact of meteorites on the surface (including dust accumulations themselves, leading to what I'd call "polymict melt breccias" by analogy with terminology for sedimentary rocks). Sometimes the impact of a (micro-)meteorite onto a (relatively) coarsely crystalline igneous rock's phenocrysts can also release unmelted crystal fragments in the "dust" grain size range.
The amount of "dust" released by "radiation" ... I don't think it's going to be very high. The most energetic component of the radiation spectrum is iron nuclei accelerated by galactic magnetic fields to moderate relativistic speeds. From the PoV of a DNA molecule, they're pretty big impacts - double-strand break, easily. From the PoV of a dust grain though - enough to accelerate one to bullet-like speeds, maybe. Which would give it penetration range of a few particle diameters in a loosely compacted sediment.
By definition, these stories are always about finding a cave that is close enough to the surface to have been breached by a seismic event (remote impact) or a more-or-less direct impact. That's going to mean there have been millennia for the dust to diffuse a long way into the lava tube caves - particularly if the grains have a bit of extra lift due to photoionisation by solar UV light.
Another rarely heard but relatively realistic strategy has been of following a cave's surface expression due to the roof sagging, which produces a "sinuous rille". But that "sagging roof" also means that the roof is fractured, which will allow the dust to penetrate into the cave, often many km from any visible entrance.
The surface expression also means that the roof is fractured, and essentially certain to not be vacuum tight.
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The surface expression also means that the roof is fractured, and essentially certain to not be vacuum tight.
Not that the roof is the only concern. The gigantic tidal stresses Earth exerts on Luna means that all of its rock is littered with fractures. Major voids within the rock will essentially never be air tight in consequence. "Living in a Lunar cave", even (or perhaps especially) a large lava tube doesn't mean slapping a door on the front and filling it up with air. Air will leak out every which way.
In theory a lava tube could be sealed up by spraying the entirety of its surface with a vacuum-tolerant seal
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Not gigantic stresses - forces. The forces on the Moon are large. The forces per unit area - dimensions of pressure or stress, N.m^-2 - are not so large. But they're big enough that many thermal fractures (from the cooling of igneous rocks from just below their melting point to the couple of hundred Kelvin (variable) of their current environment. are not going to have had the opportunity to ever heal, and
Re: Dust (Score:1)
solved problem, we have mines on Earth with areas having similar
Sci fi (Score:5, Insightful)
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It seems like an un-invention. Our ancestors were all over this and I have the charcoal paintings to prove it.
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The Lava Tubes they mention have serious potential since the lower lunar gravity would allow them to grow nearly a quarter mile wide [wikipedia.org]
The effort would be put into coating the interior to make it air tight and habitable, nothing is free, but it is nice when much of the work has been done by a natural process.
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A roof a quarter mile wide would be an extremely low margin-of safety structure. Doubly so since it would pretty much need to be in a lava flow a few tens of metres thick, so ... what's that arch profile? A "quarter-mile" is what? 400 metres. So a profile of about 20:1? I might trust that in a pr
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Have you ever given thought to the proportion of our "cave man" ancestors that ever saw the inside of a cave? For the UK (whose geology I know better than mainland Europe or America outside Appalachia), I'd estimate perhaps a couple of percent.
Before (probably) 20~40 kyr ago, most early humanoids would have lived in the open, or under branch+ leaf-thatch lean-to type shelters. From about 40 kyr, stitched leather and/ or greased woven fabric as a "tent" material (plus-or-minu
The Economist, not sci-fi (Score:1)
TFA was published in The Economist, and this is what makes the story interesting
Sooner or later, any such endeavour will need financing - and those decision-makers are more likely to read business press than astrogeology journals...
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Same here. I recall something about a pressurized cavern in which people would strap on mechanical wings and fly around in 1/6 gravity.
Re: Sci fi (Score:2)
Robert A. Heinleinâ(TM)s The Menace From Earth had parks where people would strap on wings and glide inside a large cavern.
His novel The Moon is a Harsh Mistress was about a rebellion. The moon had been set up as a prison colony similar to what Britain did with Australia and the rebellion was due to the continued oppression of the descendants of the original prisoners.
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Robert A. Heinleinâ(TM)s The Menace From Earth had parks where people would strap on wings and glide inside a large cavern.
Came to mention this - it's possibly my favourite Heinlein story. It's also one of the very few stories I ever read that actually gave me an interest in having an off-Earth vacation if the opportunity ever arose.
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But always remember: (Score:5, Informative)
The Moon Is A Harsh Mistress.
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If you had remembered it, you'd know that Heinlein's Moon's tunnels there were carved by the prisoners following seams of ice within the regolith, which then needed to be lined to be pressurised.
Personally, I never understood why Heinlein's miners didn't do "pillar & stall [wikipedia.org]" mining, since the ice is clearly in somewhat continuous beds at relatively shallow depths (they ge breached by missiles from Earth), but too deep to be worth the effort of ope
Pressure takes Strength -- overburden (Score:3)
I doubt the math works for anything approaching normal human tolerances -- 14.7psia (101kPaa) at sea level. All that area makes alot of force to resist. If lunar regolith/basalt has a density ~2 in the 1/6 gravity, the tube will have to have least 100ft (30m) of cover over the top. And that's with zero safety factor, but humans are OK with less pressure, say 10psia so that give some safety factor. Much lower pressures might be OK with oxygen masks.
Re: Pressure takes Strength -- overburden (Score:4, Insightful)
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I was assuming some kind of liner to eliminate leaks through fissures. If you mean as full pressure retaining (hoop-stress), the aluminum will have to be approx 0.1% thick of the tube diameter. So 1.2" for a 100ft tube. That's alot of aluminium.
Re: Pressure takes Strength -- overburden (Score:1)
That's alot of aluminium.
By your own admission, you'd only need to line the more shallow sections - and those wouldn't need to be 100' wide. You're probably going to want to fuse that regolith, however.
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Yes, aluminum (or steel if you can find iron) pressure-vessels would be quite usable for things like entrances and connectors. Regolith as deadweight would not need fusing beyond structural irregularities and the internal gas-tight membrane.
Would need a lot of materials, but different ones? (Score:2)
From there, use UHMWPE habitats coated
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Care to calculate the energy you'll need to do that fusing? If your regolith is basaltic (on the maria), it'll melt at around 1300 K ; if it's anorthositic (in the "Highlands"), it'll be more like 1400~1500 K.
The tonnages you'll require will be substantial. Say, 5m diameter pressure vessels (humans plus some utilities) with a couple of metres of fused regolith above/ around the "edge" units. I make that some 30 tonnes of regolith above each linea
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I wouldn't even necessarily go with aluminum. Some sort of spray liner, something a bit like latex. Maybe a couple layers. An idea I have is that you do multiple coatings. First coats are designed to penetrate and strengthen the rock. Next you pressurize just a bit, and do a coat with something like the "leak stop" you put in car tires, so that the sealent gets into any cracks and pores really good. After that, something similar to latex, but designed to last longer and seal better.
The rock provides
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Aluminum would be a much better gas barrier than latex or it's equivalent. Probably something like a sandwich with layers of aluminum foil between layers of a tough flexible material would work. Just think of how much longer mylar-aluminum-mylar balloons stay full compared to rubber balloons.
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Remember that I said "a bit like latex" and "similar to latex" while specifying "designed to last longer and seal better". You're not saying anything I don't know. But of common materials, latex is probably the closest material most people know about that could be sprayed on to provide an air seal.
The main problem an aluminum sandwich material is that it'd be a sheet, not something you could just spray. I mean, it's a possibility, but you'd have problems, I think, with sealing the edges. It'd take a lot
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The main problem an aluminum sandwich material is that it'd be a sheet, not something you could just spray.
You're not thinking big enough, or considering conditions. It's a low gravity environment where surface tension dominates and it's a pretty hard vacuum. Spraying liquid aluminum is not just feasible but desirable. There's no air to oxidize the droplets or interfere with their dispersion and gravity is low enough that surface tension will hold it in place long enough to cool and solidify on walls and even ceilings. Aluminum is relatively ductile as metals go, so it will tolerate a certain amount of moonq
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Some sort of spray liner, something a bit like latex.
A spray liner would surely save labor, but you won't be using anything remotely like latex. Latex is an emulsion that only coagulates when exposed to air. In a vacuum, it turns to powder. It's 55+% water, which boils off.
There is no polymer liner that tolerates the conditions to be safe for long enough to be worth the effort of deploying it. Polymers outgas quickly in vacuum (~100 hours) and subsequently become brittle.
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Can you remember approximately how rough the walls were inn the last lava tube cave you explored was? Or how irregularly shaped? No.
It's going to be an extremely complexly-shaped aluminium liner. Or it's going to be a simple circular cross section exactly (and I don't mean "approximately") the same size and shape as the ones used in surface encampments around and over which loose soil is piled as a radiation shield.
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I would think for ballistic protection 100' would also be a minimum. No idea what the compressive strength of the basalt would be...
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If a lava tube has survived since there was active volcanism on the moon (a billion+ years) it's a pretty good indication that it offers enough "ballistic protection" to last any human-relevant period of time. You'd be more likely to die from an asteroid impact on Earth.
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Did you try to do the math? According to the actual scientists who did some actual math on this topic, "a lava tube with a roof thickness of ten metres could be safely pressurised to almost the same conditions found at sea level on Earth."
There are no lava tubes that go through regolith, by definition. The roof is formed as the lava cools into solid rock on top, while it keeps flowing underground.
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Assuming that you found a section with the remarkable wall-rock integrity to be vacuum tight in all directions ... or that you coated the walls somehow to do that. Which would be a major undertaking.
Speaking as someone who has moved rock debris from blasting (trying to find where that water is going - we know there is upwards of 100cu.m of air-filled hole in this undergrou
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Speaking as someone who has moved rock debris from blasting (trying to find where that water is going - we know there is upwards of 100cu.m of air-filled hole in this underground catchment area) around underground ... that's going to be a daunting piece of work.
- Doubly daunting to do it wearing diving suits on the far side of a flooded section of cave - but I know people who have done that. (My cave diving confidence was never that high.)
- Doing it in a space suit, in a vacuum? Whoever is safety coordinator for planning that job ... has a job I do not want.
So daunting I would suggest not doing it. For that, we can and will use machines. They don't even have to be sophisticated robots. Big dumb mining machines are excellent at moving rock debris.
I don't know why we persist in conceptualizing off Earth settling activity like the American Old West. We are not doing this with a handful of guys in shirt sleeves with shovels, axes, and saws. We have got to stop letting history pollute our thinking. If we are to succeed off Earth, we are going to bring to bear
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Big dumb mining machines have humans at the controls. I'll grant that, on Earth, the controls are generally in the machine, but with a root-and-branch redesign, you could move the controls to a console at the other end of a fibre optic cable. Possibly a console still on the surface after you've lowered your big dumb mining machine into the pit using a sky hook to support the winch cable from above the middle of the hole, but that's a problem to be
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Uh, did you just calculate the basalt necessary for gravity to hold the rock down against air pressure?
The idea with lava tunnels is that it isn't regolith, it is solid rock other than the tunnel in it. The rock itself will have tensile strength.
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Re: Pressure takes Strength -- overburden (Score:1)
why don't you read some studies first? tensile strength of lunar lava tube "rock" 6.9 MPa.
As for civil engineering we tunnel through "rock"
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6.9 MPa is 1000psi -- sounds like a read-across from similar earth material, not tested sample. Furthermore, it looks like one of those made-up numbers. Actual intact basalt is much higher but de-rated for defects.
As for tunnelling, the bores are circular so material is in compression where fissures are less relevant.
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But the great thing is lunar tubes will be entered and analyzed one day, perhaps robotic ally.
They seem to thinkk plenty of lunar tubes have circular or elliptical cross section with arched roof great for load bearing. They (analyzers of LRO data) don't seem to think fissure and defects big enough deal, that there are long stretches that won't have them.
Some rock has less than half that 6.9 MPa tensile strength and we tunnel in it.
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Which lunar lava tube was that sample taken from? On which mission. Where is the paper detailing the tests and measurement methods?
Or, did someone pull that figure out from another source, and hand-wave that this testing-machine-sized "hand specimen" would be representative up to something human height vertically and tens to hundreds of times that size horizontally?
Hmmm, that's actually a rather large assumption. Brobdingnagian, even, which is a word that
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you seem to be confused. obviously the properties of real tubes will be tested in coming missions.
NASA is much smarter than you. People who get engineer things for off world use dont don't care what the likes of you deem impossible
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But much more likely, there won't be any suitable potential caves close enough to be worth the effort of deviating from SOP (Standard Operating Practice) to install an abnormal base in an abnormal location.
"Close enough" would be about an hour's surface travel from [something desirable). The cost of deviating from the norm is hard to estimate, but it's not going to be minor.
I haven't claimed it's impossible (
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"Solid" rock generally isn't.
Even igneous rocks like basalt and granite have porosity of a few tenths of a percent. Low permeability, of course. Until you take the naturally omnipresent fractures into consideration.
I used to find oil for a living. Typically, you want to find a reservoir rock with at least several percent by volume of porosity. But I have drilled, and tested for producibility, basalt-dominated sections of several hundred metres, and got potentially economic amounts of gas o
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I see no particular reason to hope that Lunar basalt would be much better, for holding tight against a vacuum. But hey, I work with real rocks, not theoretical approximations.
Oh, I think you read way too much into my post if you think that I don't understand that the rock is likely porous.
For example, I posted this yesterday. [slashdot.org]
You misunderstood the point of my post. redelm posted an estimated thickness/depth requirement of such depth that 1 atmosphere's worth of pressure would be equaled(more or less) by the sheer mass on top of it, adjusted for the moon's gravity. That is, of course, completely unnecessary. Only about 10 meters of rock would provide all the strength necessary,
water (Score:2)
Bad idea (Score:2)
"Creating Colossal Cave Systems" (Score:5, Funny)
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Until the inevitable war ... (Score:2)
or terrorist attack. It would not take much to blow a hole in one of these tubes and thousands would die. We are, unfortunately, not a very nice species.
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or terrorist attack. It would not take much to blow a hole in one of these tubes and thousands would die. We are, unfortunately, not a very nice species.
Really? You think that pressure doors and bulkheads don't exist even now? Have you yet to read any science fiction set on the moon?
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A pressure door of bulkhead that big would be hard to build as well as vulnerable to further attack. It is different from a blast on Earth where you might destroy a building of few, on the moon a hole might depressurise a whole cavern and kill everyone inside who cannot get into a pressure suit or building within a minute or so.
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A pressure door of bulkhead that big would be hard to build as well as vulnerable to further attack. It is different from a blast on Earth where you might destroy a building of few, on the moon a hole might depressurise a whole cavern and kill everyone inside who cannot get into a pressure suit or building within a minute or so.
I think you're severely underestimating the size of the hole you would need to make in order to rapidly depressurize a cavern of the size we're discussing. Consider the square-cube ratio. As the size of a three-dimensional geometric shape increases, the ratio of the volume to the surface area increases. So, to rapidly depressurize, you need a larger hole. So large, in fact, that pretty much any method for making such a large hole you might have (i.e. explosives) will generate such a large explosion that fir
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CERN used to state this about visiting:
"Tours are not allowed down into the actual Hadron Collider underground tunnels while it is in operation."
This policy is likely still in place, even though it has been removed from their web page.
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Darn. There goes my dream of roasting (exploding?) marshmallows in the beam.
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Did you know that it's also possible to detonate bombs on Earth, and there are locations with high population density? Yet this doesn't stop people from living here.
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It's not like they have much choice. Where else are they going to live?
You smell a wumpus nearby (Score:2)
n/t
Living inside the tubes of airless moon? (Score:2)
https://www.youtube.com/watch?... [youtube.com]
Not a new idea (Score:2)
Been mentioned before, as has the idea of digging pits, pressurized structures, making concrete etc. Concerning lava tubes, presumably they go pretty much down which doesn't necessarily help much either. Probably needs a mission or two to identify some tunnels and see what's in them - water, minerals, life even - and if they're viable for habitation.
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Why would you presume that lava tubes go down? Every lava tube I've walked through on Earth has been very horizontal, unlike most of the non-volcanic caves I've been in which have usually been more vertical... except for ones formed by water washing out a tunnel. Like water, lava tends to create a sort of horizontal stream bed.
Moonquakes and Micro-Cracks (Score:3)
The moon does have moonquakes, and whatever rock the lava tubes are lined with is likely brittle. Those caves would most definitely have to be lined with something. First it isn't likely that they are airtight to begin with, and they won't stay that way even if they were at first. The lining would have to be flexible and ductile to withstand any shifting.
If these are pressurized and a moonquake hits, as small as the quakes are compared to earth, it is quite likely they will create a lot of cracks. Even as micro-cracks given enough surface area I would hazard a guess that it would result in a significant and continuous atmospheric loss that would have to be continually made up for. And yes, we can get oxygen from water from shielded areas on the moon's south pole, but it's not like earth, that water is limited. Then there is the fact that we require nitrogen in our atmosphere. We can breathe pure oxygen but that isn't practical unless you want everything to burst into flame in these caves at some point. There is no way to stop that from eventually happening given we need electricity to power things, and one spark... (Oxygen is very dangerous in its pure form, for example if you are building a high pressure O2 line and have oil left over the line, as part of the pipe cutting and threading operations that happen when constructing complex gas lines in a facility, it will auto-ignite and and explode; it's why there are very specific regulations on how these pipes must be cleaned before they may be used with O2). The short of it is we need Nitrogen as well in large quantities, or some other non-combustible filler gas. That will be hard to come by even if it can be extracted from minerals on the moon, and so we don't want to lose that as well.
And then there is containing the pressure. Even at less than earth standard atmospheric pressure (101.3kPa, 760mm Hg, 14.7 PSI, whatever), the pressure being exerted on the walls (article says 1 km wide chamber) will be enormous. Those caves would have to be extremely deep in order to prevent them from exploding into space. Even deeper to stop a cascading effect from moonquake induced cracks especially if from a nearby meteor impact. We have a big atmosphere over earth to burn up any asteroid smaller than 5 to 10 metres (the Chelyabinsk meteor was 15 metres wide but came in at a shallow angle). When it exploded 30 km high in the atmosphere, the energy it released was between 400 and 500 kilotons of TNT or around 30 times Hiroshima. If that hit in the region of one of these tubes, it would be all over. Just too much pressure to contain without a highly resilient and ductile liners that could shift and move. Of course if one of these, even smaller, hit close by who knows. So there would need to be a very effective anti-meteorite defence system set up as well, because obviously, there is no atmosphere on the moon to burn these up.
All these issues exist regardless of what you build a moon settlement out of. As for Mars, they don't have hardly any quakes. There is no tectonics, and it is so much bigger that unless a really big meteor hits, the mass of the planet will dampen the blow.
Yeah, I'm not a planetary expert, but one does read about things and one can think.
Gentlemen, Be Seated! (Score:3)
Thanks for the insightful and informative post. Some 1940's hard-sci-fi humor by Heinlein in reply describing one option for when cracks occur: :-)
https://en.wikipedia.org/wiki/... [wikipedia.org]!
"The story tells of a visit to a tunnel on the surface of the Moon which goes awry when a pressure seal fails, trapping three men (a supervisor, a reporter, and a tunnel worker). The title of the story derives from the way they plug an air leak while awaiting rescue: by sitting on it."
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My only significant quibble would be that a moonquake (or seismic waves from an impact elsewhere on the Moon - which happens more than monthly) is much more likely to open and move pre-existing cracks than to create new ones. The lava flows which these tube caves are found in would have fractures spaced on the order of the spacing of cooling fractures in columnar b
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If these are pressurized and a moonquake hits, as small as the quakes are compared to earth, it is quite likely they will create a lot of cracks. Even as micro-cracks given enough surface area I would hazard a guess that it would result in a significant and continuous atmospheric loss that would have to be continually made up for. And yes, we can get oxygen from water from shielded areas on the moon's south pole, but it's not like earth, that water is limited. Then there is the fact that we require nitrogen in our atmosphere. We can breathe pure oxygen but that isn't practical unless you want everything to burst into flame in these caves at some point. There is no way to stop that from eventually happening given we need electricity to power things, and one spark... (Oxygen is very dangerous in its pure form, for example if you are building a high pressure O2 line and have oil left over the line, as part of the pipe cutting and threading operations that happen when constructing complex gas lines in a facility, it will auto-ignite and and explode; it's why there are very specific regulations on how these pipes must be cleaned before they may be used with O2). The short of it is we need Nitrogen as well in large quantities, or some other non-combustible filler gas. That will be hard to come by even if it can be extracted from minerals on the moon, and so we don't want to lose that as well.
I think your understanding of how oxygen and combustion work is a little off. It's almost all about the oxygen partial pressure. In our atmosphere, the oxygen partial pressure is about 3.1 PSI out of a sea-level atmosphere of about 14.7 PSI. If you pressurize the atmosphere to 14.7 PSI with pure oxygen, that's not physiologically healthy for humans anyway. You want the oxygen partial pressure to the same regardless of what other gases are present. The Apollo 1 experiment, which did result in a fire, was tra
Lava tubes bad (Score:2)
Lava tubes would be structurally unstable and leaky because of billions of years of asteroid impacts fracturing the bedrock. It would be much safer to pile a meter or two of lunar rock over an engineered arch, which equates to less then 1/3 meter (about a foot) under Earth gravity.
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1- how low do you want the radiation level in the habitat. You can have neutrino lab levels (as we go through under-Alpine tunnels and disused nickel mines to attain on Earth), or you can have the radiation levels reached by crew on Europe-Japan commercial flights, whose managers have to juggle their schedules to avoid having to classify them as "radiation workers" (hint - as much paperwork as for qualifying a pilot).
2- what your "shieldin
east of the mare (Score:2)
colossal cave systems that are up to a kilometre across and hundreds of kilometres long
You are in a lava tube near the opening.
The regolith is crunching under your feet.
> WEST
There is no atmosphere in that direction.
Your lamp has gone out.
The Boring Company (Score:2)
It was never just for Earth.......
-m
Boring (Score:2)
Who could imagine it? (Score:2)
I mean, other than scientists, engineers, and sf fans since at *least* the 1950's?
Certainly not, say, Heinlein, in Moon is a Harsh Mistress (1966). No, no, this is all a brand new idea.