Author Topic: Envisioning Amazing Martian Habitats  (Read 870013 times)

Offline nacnud

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Re: Envisioning Amazing Martian Habitats
« Reply #1220 on: 10/15/2017 03:15 pm »
I think the water ice and the lava tubes are in different places...

Water ice is at high latitudes and low altitudes, features possibly associated with lava tubes are at low latitudes and high altitudes - specifically the tharsis bulge and the big volcanoes there.
« Last Edit: 10/15/2017 03:21 pm by nacnud »

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #1221 on: 10/15/2017 04:12 pm »
Map from a paper on Lava tubes.  Dark blue dots are tubes.

http://marsed.asu.edu/sites/default/files/msip_reports/Martian%20lava%20tubes.pdf

And as a little decoration, my take on an elliptical dome

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #1222 on: 10/15/2017 04:21 pm »
Map from a paper on Lava tubes.  Dark blue dots are tubes.

http://marsed.asu.edu/sites/default/files/msip_reports/Martian%20lava%20tubes.pdf

And as a little decoration, my take on an elliptical dome
Oh, wow, a low altitude lava tube! That might actually be worth checking out. The others are too high altitude, which is bad for a bunch of reasons.
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Offline Dao Angkan

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Re: Envisioning Amazing Martian Habitats
« Reply #1223 on: 10/15/2017 04:26 pm »
Water may be more widespread than those lower resolution maps suggest.

Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data

Quote
We present a map of the near subsurface hydrogen distribution on Mars, based on epithermal neutron data from the Mars Odyssey Neutron Spectrometer. The map’s spatial resolution is approximately improved two-fold via a new form of the pixon image reconstruction technique. We discover hydrogen-rich mineralogy far from the poles, including  ∼10 wt.% water equivalent hydrogen (WEH) on the flanks of the Tharsis Montes and  >40 wt.% WEH at the Medusae Fossae Formation (MFF). The high WEH abundance at the MFF implies the presence of bulk water ice. This supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface. We find the young undivided channel system material in southern Elysium Planitia to be distinct from its surroundings and exceptionally dry; there is no evidence of hydration at the location in Elysium Planitia suggested to contain a buried water ice sea. Finally, we find that the sites of recurring slope lineae (RSL) do not correlate with subsurface hydration. This implies that RSL are not fed by large, near-subsurface aquifers, but are instead the result of either small ( < 120 km diameter) aquifers, deliquescence of perchlorate and chlorate salts or dry, granular flows.
« Last Edit: 10/15/2017 04:30 pm by Dao Angkan »

Offline nacnud

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Re: Envisioning Amazing Martian Habitats
« Reply #1224 on: 10/15/2017 04:41 pm »
Interesting, but needs to be taken with a pinch of salt. (groan :) )

"Our result is consistent with the lower member of the MFF containing ice rich material, which lends weight to the theory that, at least part of, the Medusae Fossae Formation (MFF) is a polar layered-like deposit. Salt hydrates could also explain the observations as they have up to 50 wt.% water equivalent hydrogen, but their stability in the Martian regolith has not been demonstrated (Bish et al., 2003). No detections of hydrated minerals within the MFF are reported in either CRISM or OMEGA data sets (Carter et al., 2013)."


Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1225 on: 10/16/2017 02:24 am »
I found a paper that links pit chains to a certain type of faulting.
Distribution, morphology, and origins of Martian pit crater chains

Rilles associated with faulting has also been suggested as a mechanism on the moon. But rilles and pits associated with tunnels seems to be limited to lava tubes.

Note that the paper is talking about a different type of pit chain.

See the differences between their type and what I showed:

[Theirs]







[Mine]




Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1226 on: 10/16/2017 02:28 am »
Martian lava tubes, and do we have any evidence that there is plenty of the critical water resource nearby?

If you mean my idea of water ice preferentially collecting inside the tubes, then no. Zero data. It's just something I'm proposing from first principles. (I have seen other suggestions that lava tubes might collect melt-water run off, I haven't seen anyone suggest the same mechanism I'm proposing.)

Providing evidence would require pretty close examination, it's not something you could detect from orbit. (Too localised for deep scans that map broad areas, too hidden for fine scans that map surface composition.) But if my hypothesised effect exists, it should work in any lava tube, so a single robotic visit to a single site should prove/disprove the idea; and they are generally interesting features anyway.

Once it's cheap to get to Mars, throwing low-cost and relatively mass-produced robotic rovers around should become more common. In the window between cheap transport and human settlement, someone will hopefully have a look.

If it exists, then there's multiple sites with megatonnes of fairly pure ice (not hydrated regolith, or frozen aquifers, or buried glaciers) in an easily mined form (probably as firn), in a location that's extremely convenient for settlement (a pre-existing tunnel through a layer of hard basalt.)



I think the water ice and the lava tubes are in different places...
Water ice is at high latitudes and low altitudes, features possibly associated with lava tubes are at low latitudes and high altitudes - specifically the tharsis bulge and the big volcanoes there.

Again, my suggestion of a link between lava tubes and water is based on the temperature inside the tubes, it is unrelated to the broad distribution of hydrogen in the regolith.

Offline vaporcobra

Re: Envisioning Amazing Martian Habitats
« Reply #1227 on: 10/16/2017 04:07 am »
And what will get to mars first. Earth movers(bulldozers) or tunnel borers?
Just put the bigelow modules in the tunnel.
Best to just forget about Bigelow for SpaceX's Mars plans, IMHO. The BFS itself is cheaper for habitable volume than a Bigelow module is, even including all the useless overhead of all the fuel tanks and engines and stuff.

For the record, I'd bet on earth (regolith) movers, first.

Yes, bulldozers first. Need to smooth regolith for landing pads, roads, and structures. Cut and cover for habitats would be an easy way to add protection. If there's not a convenient steep hill or cliff nearby, they'll need a bulldozer to cut into the regolith deep enough for the tunnel borers to get started.

If SpaceX or a separate company is already going to have to design their own heavy machinery from scratch to optimize for mass, having separate machines is wasteful. I'd expect that wherever possible, a modular base with swappable tools will be preferred. 1/3rd Earth gravity will also spice things up considerably.

Offline Lumina

Re: Envisioning Amazing Martian Habitats
« Reply #1228 on: 11/07/2017 06:36 pm »
If you have pressurised habitats inside a dome, then you can get away with pressurising the dome a lot lower. 0.07atm is above the Armstrong limit, so no need for a pressure suit "outside", and the triple point of water is ~40°C, so you can have lakes etc. A breathing mask would still be required. External pressure at the bottom of a deep canyon such as Melas Chasma should be ~0.01atm.

For a minimally breathable atmosphere you could probably get away with ~0.2atm.

You could have pressurized habitats inside a partially pressurized dome, but the bigger question is why would one want to do that... it seems that on an apples-to-apples basis, partial-pressure domes provide less habitable volume for a higher lifetime cost and more system complexity. Of course, a partially pressurized dome would be good for a greenhouse.
« Last Edit: 11/07/2017 06:37 pm by Lumina »

Offline nacnud

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Re: Envisioning Amazing Martian Habitats
« Reply #1229 on: 11/07/2017 06:49 pm »
If you have pressurised habitats inside a dome, then you can get away with pressurising the dome a lot lower. 0.07atm is above the Armstrong limit, so no need for a pressure suit "outside", and the triple point of water is ~40°C, so you can have lakes etc. A breathing mask would still be required. External pressure at the bottom of a deep canyon such as Melas Chasma should be ~0.01atm.

For a minimally breathable atmosphere you could probably get away with ~0.2atm.

You could have pressurized habitats inside a partially pressurized dome, but the bigger question is why would one want to do that... it seems that on an apples-to-apples basis, partial-pressure domes provide less habitable volume for a higher lifetime cost and more system complexity. Of course, a partially pressurized dome would be good for a greenhouse.

See the second post in this thread :)

Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1230 on: 11/07/2017 07:16 pm »
a partially pressurized dome would be good for a greenhouse.

Not really. I forget the reference, it's probably somewhere in the Scaling Ag thread, but in reduced pressure environments, the critical limits (ie, the minimums and maximums) tend to approach each other; resulting in the plants becoming much "fussier" about their environment.

(Also, "dome". Reduced pressure merely makes a bad idea easier; it doesn't turn it into a good idea.)

[Edit: By "minimums and maximums", I mean the level of something that allows growth vs the level that causes toxicity. For example, plants have a minimum amount of CO2 required for growth, any less and they become dormant. But they also have a maximum level, beyond which the leaves will acidify and "burn". The former is related to partial pressure, the latter to relative gas percentage. Hence, when you lower the air pressure, the percentage of CO2 required to stay above the minimum partial pressure for growth increases; drop the pressure enough and it will exceed the percentage that causes acidification of the plant tissues. Similar things happen with other requirements, such as water. As you lower the air pressure, plants require more water to achieve the same growth. Drop the pressure enough, and plants enter their drought state regardless of how much water is available.]

[[To a certain extent, plants are more delicate than people.]]
« Last Edit: 11/07/2017 07:43 pm by Paul451 »

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #1231 on: 11/08/2017 02:28 am »
A dome is good for multiple reasons. First, it gives you pressure vessel redundancy. A big increase in safety.

Second: it can be pretty cheaply made, lightweight and makes construction of stuff inside a LOT easier as you can use nearly unmodified Earthside equipment.

Third, and depending on the makeup of the atmosphere inside, it greatly increases living space and reduces the feeling of claustrophobia.

fourth: it's cool. We're not going to Mars for our health, we're going because it's cool. So gotta maximize that.
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Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1232 on: 11/08/2017 03:19 am »
A dome is good for multiple reasons. First, it gives you pressure vessel redundancy. A big increase in safety.

Except domes aren't pressure vessels, that's their problem.

I'm not arguing against the idea of using a partial pressure environment to allow large volume at a lower cost (it might be useful, it might not, that's a different debate), just that domes are a really, really stupid way of doing it.

Second: it can be pretty cheaply made, lightweight

Not if you actually want to hold an atmosphere (even a partial one), then they need more construction to hold them in place than any proper pressure vessel. Making them more expensive, complex and fragile than alternatives.

You can force domes to work, by creating over-engineered anchors, by sufficiently sealing the floor, by reinforcing the rim, etc etc. For what? To expensively gain the same volume that could be vastly more easily gained by using a proper pressure vessel.

The only reason people suggest domes is that, like you no matter how many times we go over this, they always have this image in their heads that domes are "easy". Just throw together a few panels, or a plastic sheet, add some air, and viola! instant Martian/Lunar habitat. And, like you, no matter how many times we go into the details of why domes are just the dumbest concept for pressure-vessels, somehow as soon as the subject changes, they go back to that mental image of the easy dome on Mars or the Moon. It's almost like a very specific anterograde-amnesia (where people can't form new memories.)

Can't you guys get a tattoo or something? Keep a special notebook? Have a little macro pop-up on your computer wherever you type d-o-m-e, with a quick summary of why domes are stupid, and a counter showing how many times it's had to do that?

Offline KelvinZero

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Re: Envisioning Amazing Martian Habitats
« Reply #1233 on: 11/08/2017 03:58 am »
I learn just to translate "dome" in my head to one of the various dome-like substitutes that seem acceptable to me. It could be a buried sphere or oblate sphere, it could be a dome anchored to an entire underground city. I think it is quite likely that "domes" is exactly what it will look like from the surface.

Unlike the Moon vs Mars debate, there is not even the theoretical possibility of getting stuck in "dome boondoggle", so it doesn't bother me that much.

It is only a pity that newbies who have not seen the threads on this may be left with the impression that you can put up a dome just like pitching a tent, and won't get a feel for the huge 5-10 ton/m2 pressure that will be dealt with one way or another.


Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1234 on: 11/08/2017 04:14 am »
It is only a pity that newbies who have not seen the threads on this may be left with the impression that you can put up a dome just like pitching a tent

Robotbeat, and others who keep bringing them up, are not newbies. And they don't mean "a proper pressure-vessel of deceptively dome-like appearance due to its placement".

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #1235 on: 11/08/2017 04:17 am »
A dome is good for multiple reasons. First, it gives you pressure vessel redundancy. A big increase in safety.

Except domes aren't pressure vessels, that's their problem.

I'm not arguing against the idea of using a partial pressure environment to allow large volume at a lower cost (it might be useful, it might not, that's a different debate), just that domes are a really, really stupid way of doing it.

Second: it can be pretty cheaply made, lightweight

Not if you actually want to hold an atmosphere (even a partial one), then they need more construction to hold them in place than any proper pressure vessel. Making them more expensive, complex and fragile than alternatives.

You can force domes to work, by creating over-engineered anchors, by sufficiently sealing the floor, by reinforcing the rim, etc etc. For what? To expensively gain the same volume that could be vastly more easily gained by using a proper pressure vessel.

The only reason people suggest domes is that, like you no matter how many times we go over this, they always have this image in their heads that domes are "easy". Just throw together a few panels, or a plastic sheet, add some air, and viola! instant Martian/Lunar habitat. And, like you, no matter how many times we go into the details of why domes are just the dumbest concept for pressure-vessels, somehow as soon as the subject changes, they go back to that mental image of the easy dome on Mars or the Moon. It's almost like a very specific anterograde-amnesia (where people can't form new memories.)

Can't you guys get a tattoo or something? Keep a special notebook? Have a little macro pop-up on your computer wherever you type d-o-m-e, with a quick summary of why domes are stupid, and a counter showing how many times it's had to do that?

Domes are great pressure vessels.

Look, I remember that long thread arguing about anchors, etc.

All amateurish and arm-wavey. Didn't convince me in the least.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Lar

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Re: Envisioning Amazing Martian Habitats
« Reply #1236 on: 11/08/2017 09:51 pm »
Tattoos? Tattoo this somewhere handy. Be excellent to each other. Snark isn't needful. Thanks
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #1237 on: 11/09/2017 03:19 am »
Air-supported structures are used often for sporting events especially in northern climates during the winter.

They normally operate at 0.35psi. Mars surface pressure at Hellas Basin is 0.18psi. The Armstrong Limit is 0.91psi, so even if you're just building stuff or growing plants, you'd want more than that. Probably more like 1.75psi to give a margin of safety. That's still closer to air-supported structures on Earth than it is to a full sea level pressure station module. Domes are feasible.

Some leakage is fine for some purposes, like growing plants or preparing buildings.

Instead of white plastic, you could make them using ETFE so they're clear.

With Zylon or carbon fiber cables, you could build a very large dome for relatively low mass (about 1000 tons for a square kilometer and 30 meter height, with anchors placed in the middle as well to reduce structural mass). Deep, deadman-style anchors wouldn't be too hard, either (with anchors sunk in a redundant fashion). Large blowers could keep them inflated. This would make constructing buildings way easier. And eventually you could also put a liner down to reduce leakage rates to arbitrarily low levels (so you can get rid of the blowers) and fill it with breathable air.

Might also be a good way to mine a glacier or minerals.

It'd need site prep around the perimeter, perhaps using sandbags and the like, to get a good seal. About 3 meters thick and tall sand tube around the perimeter with soil piled up a few meters tall on both sides should give a good seal. That would be in addition to the deep deadman anchors and anchors placed interspersed in the middle.
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Offline biosehnsucht

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Re: Envisioning Amazing Martian Habitats
« Reply #1238 on: 11/09/2017 07:49 am »
What would a blower built to operate on Mars and generate sufficient pressure difference looks like? The atmosphere is pretty thin ... even though you wouldn't need much added pressure, it seems like the thin atmosphere will still make this an interesting engineering challenge.

Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1239 on: 11/09/2017 04:49 pm »


Uh, those black structures are the intake fans, running at a continuous 40kW each. That suggests a bit more than "some leakage". [edit: Apparently the airflow inside the structure is around 3mph. Suggesting it cycles it's own volume approximately every 2 minutes. In other words, without the continuous airflow, it would empty in 2 minutes. And that's with a pressure explicitly only the amount needed to balance the weight of the skin, providing no additional force.]

And yes, you could drill into rock and anchor the edges down, then add a sealed floor, and otherwise try to turn a non-pressure-vessel into a badly designed pressure-vessel. For what purpose? Just design a proper, fit-for-purpose, pressure-vessel from the start. Why the continued insistence on domes?
« Last Edit: 11/09/2017 05:13 pm by Paul451 »

 

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