Processing/Collection of Water Ice on Mars

[tbellman]

Yes, FSP is the reactor. They're building it now based on what I mentioned above.

Back in 2022, NASA awarded three small contracts ($5M each) for making initial designs.  These are almost "back of napkin" level.  No building of anything involved (except stacks of paper).

Then in January this year, they awarded one contract to Westinghouse to continue their design.  According to the Westinghouse press release, this will continue the design, and "begin testing of critical technology elements".  Doesn't sound like building actual reactors is part of this contract.  (Oddly enough, this is not listed on NASA's FSP page.)

And this Westinghouse reactor is as far as I can tell not based on either Kilopower or any of the ANPP reactors.

[BN]

Yes, FSP is the reactor. They're building it now based on what I mentioned above.

Back in 2022, NASA awarded three small contracts ($5M each) for making initial designs.  These are almost "back of napkin" level.  No building of anything involved (except stacks of paper).

Then in January this year, they awarded one contract to Westinghouse to continue their design.  According to the Westinghouse press release, this will continue the design, and "begin testing of critical technology elements".  Doesn't sound like building actual reactors is part of this contract.  (Oddly enough, this is not listed on NASA's FSP page.)

And this Westinghouse reactor is as far as I can tell not based on either Kilopower or any of the ANPP reactors.

I remember seeing on the NASA website sometime in the last few years that FSP was in development, by NASA themselves. For Kilopower I know they did build hardware and had designs for a 40 or 50kw reactors, which is honestly on the low end of what we would require.

Without a small reactor, I don't think a Mars base is viable. Everyone keeps forgetting that there is dust on Mars and then is flabbergasted when the latest lander/rover without an RTG stops working.


edit*

Looks like FSP is managed by Glenn Research Center in Cleveland, managed by Todd Tofil.


Is this for the same contract you're talking about?

1.0 Introduction
This statement of work (SOW) establishes the tasks to authorize Battelle Energy
Alliance (BEA) to issue a Request for Proposal (RFP) for a Phase 1 design of a Fission
Surface Power (FSP) system with industry partners. The FSP project goals are
consistent with Space Policy Directive 6 (SPD-6), which states:
“By the mid- to late-2020s, demonstrate a fission power system on the surface of
the Moon that is scalable to a power range of 40 kWe and higher to support
sustained lunar presence and exploration of Mars.”

The Phase 1 design effort shall culminate with each successful industry team submitting
an FSP design package having engineering content sufficient to establish a high degree
of confidence in the technical maturity, schedule, and cost as detailed in Sections 3.0
and 4.0. The design package shall include estimates for the technical, schedule, and
cost requirements to design, build, and test a qualification unit (FSP-QU) and
subsequent flight system (FSP-FS). The FSP-QU shall replicate the flight unit with
sufficient fidelity to establish confidence in the key design features and demonstrate all
critical aspects of the engineering design and functionality intended for the operational
lunar unit. The FSP-QU will be nuclear fueled and should resemble a final FSP-FS in
form, fit, and function to the maximum extent possible to establish confidence that the
design will function in the expected lunar environment. Finally, the design package shall
include a hardware development plan that identifies specific nuclear facilities and
material needs for accomplishing the FSP-FS.

This is from a contract here:

https://sam.gov/opp/bf48c0125df64c80902c15a9d33e386a/view


Tofil's presentation on the design requirements from 2022 can be downloaded from the Technical Reports Server.

https://ntrs.nasa.gov/citations/20220015225

[BN]

found an update on this here
https://www.nasa.gov/centers-and-facilities/glenn/nasas-fission-surface-power-project-energizes-lunar-exploration/


“We’re getting a lot of information from the three partners,” Kaldon said. “We’ll have to take some time to process it all and see what makes sense going into Phase 2 and levy the best out of Phase 1 to set requirements to design a lower-risk system moving forward.”

Open solicitation for Phase 2 is planned for 2025.

After Phase 2, the target date for delivering a reactor to the launch pad is in the early 2030s. On the Moon, the reactor will complete a one-year demonstration followed by nine operational years. If all goes well, the reactor design may be updated for potential use on Mars.

Beyond gearing up for Phase 2, NASA recently awarded Rolls Royce North American Technologies, Brayton Energy, and General Electric contracts to develop Brayton power converters."

[TheRadicalModerate]

Water ice sublimates in all conditions on Mars except for within craters above ~70 degrees latitude, at the lowest altitudes. Water ice concentrations in regolith range from 25% at ~70 degrees latitude to near ~100% at the north pole.

Collection will likely involve autonomous machines cutting and placing blocks of ice in pressurized containers for transport south to the Mars base. Water ice will be needed for drinking, breathing and fuel production. Significant quantities may also be needed to remove perchlorates from agricultural regolith.

I'd expect them to start by using Rodriguez wells.  These have lots of tech heritage in Earth polar areas.  Drill a hole, drop a heating element down the hole with a hose, seal the hole to avoid sublimation/evaporation, and pump the water out as it liquifies.  No need for strip-mining ice.

Rodwells have well-known limitations as the cavity they're heating gets bigger, but it's almost certainly the fastest way to get going, even if it's not a long-term solution.

On the other hand, the tank size of Starship seems to have increased from 1200t to 1500t, which, at a 3.6:1 ratio, would be about 1175 tonne oxygen and 325 tonne methane.

You should plan on Block 3 Starships, which have 2300t of subcooled capacity, which translates to about 2150t of boiling prop capacity.

However, you need nowhere near that amount of prop to return a crew to Earth.  It's about 3600m/s to LMO from the martian surface, and you can do a decent transit from Mars to Earth for about 2200m/s.

Figure an inert mass of about 190t (~160t dry mass and ~30t crew module), and an average Isp of 368s (a bit of an arm-wave, but you need at least one RSL at low throttle for attitude control).  I'd assume that Cat V planetary protection regulations (the "don't bring back a space plague" regulations) will require a propulsive or free capture at Earth.  I get 820t of prop for a 7.2 month transit, and no delta-v needed to capture at Earth.  (I'm suspicious of this, but I'm too lazy to validate my model for the 90th time.  Note that the model assumes Mars and Earth are in-plane
and they both have circular orbits.  Neither of these are particularly good assumptions, especially the in-plane bit.)

But wait! There's more!  If you very lightly load the crew versions of Starship (an excellent idea if you've verified that your cargo is waiting for you--let's say 40t for crew module, in-flight consumables, and meatware), you can fill the Starship completely full before you leave Earth.  It will now land with more than enough prop to get back to LMO.  Now, if you propulsively capture, or maybe gently aerocapture, a depot into LMO, you don't need to make any prop at all on the surface for an initial mission.

You're definitely going to want to make prop eventually, but you don't necessarily need to do it for early missions.  As long as you have good boiloff reduction tech on your crew Starships, you can wait to land crews before debugging water and prop production.

Note:  All of these numbers assume conjunction-class return trajectories.  If you need to provision for an opposition-class abort, you'll need a lot more prop in LMO.  But a Block 3 depot should hold at least 2530t of boiling prop, if you re-jigger its domes to consume the cylindrical portion of its barrel.  That's enough for a purely propulsive capture to deliver about 465t of prop to LMO.  That's probably enough for any oppo-class abort you care to design.

[MickQ]

This sounds like the best plan to me, provided that initial cargo landings carry enough water to sustain the crew for the duration of the mission should water mining prove unsuccessful.

I think this is a better option than having a problem with automation resulting in having to wait for the next synod for a fix to arrive.  Human eyes and hands on the ground from the start is the quickest way to get established and operational.

[BN]

Water ice sublimates in all conditions on Mars except for within craters above ~70 degrees latitude, at the lowest altitudes. Water ice concentrations in regolith range from 25% at ~70 degrees latitude to near ~100% at the north pole.

Collection will likely involve autonomous machines cutting and placing blocks of ice in pressurized containers for transport south to the Mars base. Water ice will be needed for drinking, breathing and fuel production. Significant quantities may also be needed to remove perchlorates from agricultural regolith.

I'd expect them to start by using Rodriguez wells.  These have lots of tech heritage in Earth polar areas.  Drill a hole, drop a heating element down the hole with a hose, seal the hole to avoid sublimation/evaporation, and pump the water out as it liquifies.  No need for strip-mining ice.

Rodwells have well-known limitations as the cavity they're heating gets bigger, but it's almost certainly the fastest way to get going, even if it's not a long-term solution.

the drilling itself will cause heating and sublimation, which is why I think we need partial vacuum on the drill itself. I don't think it will be liquid water, it will be vapor.

[TheRadicalModerate]

the drilling itself will cause heating and sublimation, which is why I think we need partial vacuum on the drill itself. I don't think it will be liquid water, it will be vapor.

Just the opposite.  If you increase the partial pressure on the well by sealing it,¹ then the water will stay liquid when the rodwell heating element heats it.  Then it just stays liquid in the pocket of melt until it's pumped out.

_______
¹ Note that the ice exists in the first place because the regolith cover seals it to increase the partial pressure enough so it doesn't sublimate.  You restore that partial pressure by sealing the bore hole.

[Robotbeat]

What about a small nuclear reactor, produced both heat and electricity 24/7?  Would it not be easier than a huge amount of solar panels?  Heck, the reactor could be left on board the first Starship without offloading, and the first Starship used as a fuel depot.  Then only water would have to be mined or extracted via robotics.  At this point NASA would have to get involved with SpaceX for nuclear.  It could be a molton salt type reactor using thorium.

1) doesn’t exist yet. Would take minimum 10 years development, probably much longer.
2) doesn’t actually have a weight advantage over solar.
3) still needs deployment of a radiator. And with an active reactor, you have to either put the reactor far away from crew at all times or you have to bury it. (This isn’t the case for Pu238 RTGs, as Pu238 is almost purely just an alpha emitter.)
4) costs a lot more per watt than solar+battery.

I mean sure, we’ll probably do nuclear, but for all the reasons above, we won’t and shouldn’t /wait/ for nuclear.

[Robotbeat]

found an update on this here
https://www.nasa.gov/centers-and-facilities/glenn/nasas-fission-surface-power-project-energizes-lunar-exploration/


“We’re getting a lot of information from the three partners,” Kaldon said. “We’ll have to take some time to process it all and see what makes sense going into Phase 2 and levy the best out of Phase 1 to set requirements to design a lower-risk system moving forward.”

Open solicitation for Phase 2 is planned for 2025.

After Phase 2, the target date for delivering a reactor to the launch pad is in the early 2030s. On the Moon, the reactor will complete a one-year demonstration followed by nine operational years. If all goes well, the reactor design may be updated for potential use on Mars.

Beyond gearing up for Phase 2, NASA recently awarded Rolls Royce North American Technologies, Brayton Energy, and General Electric contracts to develop Brayton power converters."

Doing math on this, we’re talking early 2040s availability for Mars at best, ie if all goes well.

[Robotbeat]

Speaking of Americium-241 as a heat source:

Americium-241 is around $1500/gram, and one gram produces 0.12W or so, for a cost of heat of, let’s be a bit optimistic and say $10,000/Watt. Sounds like a lot, but high end triple junction space rated solar cells are $1000/Watt at 1AU, on Mars’ surface averaged over a day they’d produce less than a tenth that much, so the cost per watt is actually the same, about $10,000/Watt. Weight performance is similar, too, or actually worse. 1kg of solar at 1AU is around 150W, but on Mars averaged over a day with batteries is around 10W/kg, or a tenth that of Am-241.

So, if you’re not using SpaceX style solar arrays ($1/Watt) and you ignore the regulatory overhead of Am-241, it actually trades VERY well as a heat source cost-wise.

The issue is Am-241 has regulatory overhead, not least of all because it’s actually fissionable and has a critical mass of 50-70kg or something (less if under explosive pressure with a neutron reflector), so for safety reasons you probably want to keep each unit around 1kW of heat at most.

And while still predominantly an alpha emitter, my recollection is that it has more gammas than the same activity of Pu-238, so isn’t as safe for crew to be around.

But still, may be useful as a heat source. For electricity (not heat) production, tho, you’re still better off with solar as RTGs are inefficient, maybe 10% efficiency, so you’d be no better off cost-wise, especially with all the overhead.

Still, it may be usable for water production or backup heat.

[Twark_Main]

the power situation is fairly worked out. a ~50kw fission reactor will likely be used. we have already developed these as part of the Kilopower project, as well as Camp Century.

this is one of the best resources on this topic for crewed mars:

https://ntrs.nasa.gov/api/citations/20170002010/downloads/20170002010.pdf

Too expensive compared to solar and batteries.

When it was $10 million per kilogram (or whatever) to transport to the Mars surface then maybe kilopower made some economic sense (and maybe not even then because panels and batteries could actually be lighter), but Starship has killed that justification off.

Don't drag the ice to the sublimation oven.  Build the sublimation oven around the ice.

This is my general concept.

    1. Cover the surface with a thin membrane, burying the perimeter.
    2. Pull a vacuum (these two steps are already proven with vacuum surcharging on Earth).
    3. The ice underneath sublimates at the lower pressure.
    4. Re-deposit the (now clean) ice in a collection vessel.
    5. Recycle the heat of deposition back under the membrane, so it's used to sublimate more ice. Lots of heat in that phase change!
    6. Optionally you might expose ice by "gardening" with heavy equipment or blasting, make the membrane a solar collector (80% vs 25% efficient), or selectively insulate to reduce heat loss.

Fortunately this is very short range movement of water vapor (as mentioned above), so it does work...

don't need the membrane imo. why do you think that is necessary?

Because it sublimates a lot more ice per kilogram of equipment than an auger or tank+separation hopper. Also the auger requires 100% of the sublimation energy to come from electricity, vs the membrane which inexpensively harvests ambient solar energy.

The membrane is necessary because it's the minimal implementation of the walls of your "tank" and "separation hopper."  Nothing left to take away! 

Open pit mining doesn't work because as soon as you expose the ice it begins sublimating away. We saw this with the Phoenix lander.

https://www.jpl.nasa.gov/news/bright-chunks-at-phoenix-landers-mars-site-must-have-been-ice/

Essentially my proposal exploits this mechanism rather than trying to work against it.

[BN]

the power situation is fairly worked out. a ~50kw fission reactor will likely be used. we have already developed these as part of the Kilopower project, as well as Camp Century.

this is one of the best resources on this topic for crewed mars:

https://ntrs.nasa.gov/api/citations/20170002010/downloads/20170002010.pdf

Too expensive compared to solar and batteries.

When it was $10 million per kilogram (or whatever) to transport to the Mars surface then maybe kilopower made some economic sense (and maybe not even then because panels and batteries could actually be lighter), but Starship has killed that justification off.

could be reasonable, however a lot of the energy we will need is thermal and for that reason, RTGs are quite effective.

also, what to do in the case of a long global dust storm?

Don't drag the ice to the sublimation oven.  Build the sublimation oven around the ice.

This is my general concept.

    1. Cover the surface with a thin membrane, burying the perimeter.
    2. Pull a vacuum (these two steps are already proven with vacuum surcharging on Earth).
    3. The ice underneath sublimates at the lower pressure.
    4. Re-deposit the (now clean) ice in a collection vessel.
    5. Recycle the heat of deposition back under the membrane, so it's used to sublimate more ice. Lots of heat in that phase change!
    6. Optionally you might expose ice by "gardening" with heavy equipment or blasting, make the membrane a solar collector (80% vs 25% efficient), or selectively insulate to reduce heat loss.

Fortunately this is very short range movement of water vapor (as mentioned above), so it does work...

don't need the membrane imo. why do you think that is necessary?

Because it sublimates a lot more ice per kilogram of equipment than an auger or tank+separation hopper. Also the auger requires 100% of the sublimation energy to come from electricity, vs the membrane which inexpensively harvests ambient solar energy.

The membrane is necessary because it's the minimal implementation of the walls of your "tank" and "separation hopper."  Nothing left to take away! 

Open pit mining doesn't work because as soon as you expose the ice it begins sublimating away. We saw this with the Phoenix lander.

https://www.jpl.nasa.gov/news/bright-chunks-at-phoenix-landers-mars-site-must-have-been-ice/

Essentially my proposal exploits this mechanism rather than trying to work against it.

still trying to figure out if your concept is crackpot or genius or both. what material might be appropriate for this, and how could such an operation be automated and how do you move the operation around once that area is tapped?

I still think the auger+vacuum method makes sense to start. then shoveling high ice purity subsurface regolith into a hopper and the final stage is direct mining of ice at korolev creater, there is no issue with sublimation there.

found an update on this here
https://www.nasa.gov/centers-and-facilities/glenn/nasas-fission-surface-power-project-energizes-lunar-exploration/


“We’re getting a lot of information from the three partners,” Kaldon said. “We’ll have to take some time to process it all and see what makes sense going into Phase 2 and levy the best out of Phase 1 to set requirements to design a lower-risk system moving forward.”

Open solicitation for Phase 2 is planned for 2025.

After Phase 2, the target date for delivering a reactor to the launch pad is in the early 2030s. On the Moon, the reactor will complete a one-year demonstration followed by nine operational years. If all goes well, the reactor design may be updated for potential use on Mars.

Beyond gearing up for Phase 2, NASA recently awarded Rolls Royce North American Technologies, Brayton Energy, and General Electric contracts to develop Brayton power converters."

Doing math on this, we’re talking early 2040s availability for Mars at best, ie if all goes well.

the 10 years on the Moon is unnecessary. if humans are on Mars and they would benefit from having a reactor, it could potentially be sent there instead. early/mid 2030s seems possible, albeit unlikely given that it's space hardware.

[Twark_Main]

Moving this discussion here so it's on-topic.

This is my general concept.

    1. Cover the surface with a thin membrane, burying the perimeter.

How far away is the perimeter?

As big as you can, as big as you need.    Scale helps here by reducing per-unit perimeter leakage, but it's a relatively small effect.

How far down do you have to go to get under the water deposit?

You don't.  That's not how it works.

The perimeter is buried for the same reason as you do it in vacuum surcharging: to reduce the gas in-leakage to an acceptably low rate.

    2. Pull a vacuum (these two steps are already proven with vacuum surcharging on Earth).

    3. The ice underneath sublimates at the lower pressure.

If you pull a vacuum, then the thin membrane coats the surface of the ice.  I don't know enough about the thermodynamics of a solid covered by a membrane, but ISTM that the effective pressure will be atmospheric pressure--which is usually a couple of pascals above the triple point pressure.  So I think you're not subliming a lot of ice without lots of heat.

If the surface was perfectly flat I might worry about this, but since you'll probably be "gardening" to increase porosity I don't find this scenario plausible.

Remember we're only holding back a small pressure (far below 1 atm), so don't picture vacuum bagging on Earth. There will only be a small inward force on the membrane. You could literally just put (non-sharp) rocks in a grid and the membrane will span over them. I don't anticipate needing anything nearly so elaborate, it's just to illustrate how not-a-showstopper this is.

    4. Re-deposit the (now clean) ice in a collection vessel.

    5. Recycle the heat of deposition back under the membrane, so it's used to sublimate more ice. Lots of heat in that phase change!

You still need a heat pump to do this.  Nothing wrong with recycling process heat, but it might be better to have less of it, not more.

It's not that you need a heat pump. You're moving heat from hot to cold.

What you're hinting at is actually that the pumped water vapor itself is acting as a heat pump, making the dirt under the membrane get colder than ambient. So when heat leaks through the ground, that's actually helping to harvest ice instead of being a loss like in a conventional oven (temperature-swing) approach.

    6. Optionally you might expose ice by "gardening" with heavy equipment or blasting, make the membrane a solar collector (80% vs 25% efficient), or selectively insulate to reduce heat loss.

We obviously don't know very much about the quality of the ice under the surface.  Is it mixed with soils, or is it relatively pure?

That's the great part, when you're sublimating it you don't care about that quite so much. The purification is "built in" to the mining process.

Is it a vast expanse, with tens of thousands of m³, or is it patchier?

Again this works with both options.

How deep is the deposit?  Tens or hundreds of meters?  There are a lot of variables

Ditto, this method is insensitive to that concern.

Did you check first whether these would actually be a problem?  Or is this a "throw spaghetti at the wall and see what sticks" thing?   

Fortunately this is very short range movement of water vapor (as mentioned above), so it does work, but I don't know if it makes sense as a method of bulk water transport much beyond that.  Compared to a conventional water pipe it has extremely low fluid density, which means extremely high pipe mass and pumping power for a given mass flow rate. 

I assume you're thinking only of extremely high scale mining, on extremely large water deposits.

I don't know why you would assume that. This method is scalable to both large and small deposits.

For this to work, you have to be able not only to stake off the area you're going to mine, but also somehow seal the area you want to mine next, so it doesn't sublime away while you're waiting for the equipment to mine it to become available.  At the very least, that involves trenching all the way to the bottom of the deposit, and constructing some kind of vapor-retaining wall.

Nope. There is nothing that would cause adjacent buried ice to sublimate.

Remember that we don't have a bunch of heat leaking into adjacent dirt. Even after recycling the latent heat, the perimeter is still going to be a net cold zone due to recycling losses and temperature non-uniformity.

This is one of the big advantages of these pressure-swing (as opposed to temperature-swing) approaches.

If you have a really high quality deposit, it might make more sense to use underground mining techniques, where you can continue to the pressure of the overtopping regolith to keep thinks stable, while cutting galleries into the ice, chewing it up, and sending it to a hopper for transport to whatever refining you need to do.

That works too, but it's a lot of equipment (and wear and tear, which means spare parts). Note that for a fair comparison you have to count the first stages of the refining equipment too, because in sublimation mining a lot of refining (perchlorates etc) happens "for free."

But this is all colonial-scale mining.  I'm more interested in base-scale extraction to begin with.  That requires ~1000t of prop every 2.14y (for one return flight per synod), plus, say, maybe 100t a year for base use (assuming no water-intensive industrial processes, at least to begin with).  That's about 100t of LCH4 per year, which requires 25t of hydrogen, which is 225t/y of water.  Note that pure Sabatier reactions yield O:F=2:1, so you need some other way to lean the mixture down to 3.6:1.  You can do that with RWGS, using recyclable hydrogen as a catalyst to generate excess O2, or you can simply supply more water.  Too lazy to do the math on how much more water--say about double?  That would make prop requirements 550t/y.  Say 700t/y for all base ops.  That's roughly 2t/day.

Sublimation mining sounds great for that. The nice thing is that it frees up all those bots and heavy equipment from routine "metabolic respiration" tasks, meaning they can be used for habitat preparation and tunneling and other activities that expand the human presence on Mars.

[TheRadicalModerate]

Moving this discussion here so it's on-topic.

Sorry, I just followed the link back to your original post, not realizing it wasn't on this thread.

Rather than going point-by-point, let me try to restate my objection in a more coherent form:

Let's suppose you scrape away the overcoat of regolith, which is what keeps the ice from subliming away in the first place, and then you real quick tack down your cover.  As the ice sublimes away, the ice under the attachment point will also sublime away, undermining the attachment.

Even if you constantly re-seat the attachment, the ice just outside the attachment point will now be exposed.  Presumably, as that ice sublimes away, the regolith will slump, which will expose still more ice.  Eventually, the regolith slump will get smaller and smaller, until the rest of the ice mass self-seals.

I guess if that self-sealing process doesn't waste too much ice, you can simply move to the next area that doesn't have any slump, and continue on.

Meanwhile, let's look at what's happening at the undermined attachment point.  Unless the attachment point is constantly maintained, you'll start losing ice mass underneath it, which will limit the efficiency of the whole scheme.

That's why I was thinking it made more sense to excavate a trench down to the bottom of the ice deposit, then attach at that point.  If you're going to do that, you might as well install a hermetic retaining wall to preserve the unmined portion of the ice deposit, until you're ready to start mining it.  That retaining wall would also offer a permanent point of attachment for your membrane.

This is all much, much more complicated than a rodwell.  Rodwells in Greenland produced 38t of water per day.  That seems like more than enough for early base purposes.

PS:  If it turns out to be more convenient to recover the water as vapor, then you don't hermetically seal your rodwell bore hole.  Then the heat will sublimate the ice, and you collect the vapor from the bore hole.  But it's a lot easier to have the ice sealing your mining operation than it is the membrane.

[Twark_Main]

Moving this discussion here so it's on-topic.

Sorry, I just followed the link back to your original post, not realizing it wasn't on this thread.

Rather than going point-by-point, let me try to restate my objection in a more coherent form:

Let's suppose you scrape away the overcoat of regolith, which is what keeps the ice from subliming away in the first place, and then you real quick tack down your cover.  As the ice sublimes away, the ice under the attachment point will also sublime away, undermining the attachment.

Even if you constantly re-seat the attachment, the ice just outside the attachment point will now be exposed.  Presumably, as that ice sublimes away, the regolith will slump, which will expose still more ice.  Eventually, the regolith slump will get smaller and smaller, until the rest of the ice mass self-seals.

I guess if that self-sealing process doesn't waste too much ice, you can simply move to the next area that doesn't have any slump, and continue on.

Meanwhile, let's look at what's happening at the undermined attachment point.  Unless the attachment point is constantly maintained, you'll start losing ice mass underneath it, which will limit the efficiency of the whole scheme.

If your ore is that rich, then instead of a perimeter trench you would bring in nearby sifted regolith and bury the perimeter in a mound instead. This will accomplish the same hermetic (enough) seal.

This is all much, much more complicated than a rodwell.  Rodwells in Greenland produced 38t of water per day.  That seems like more than enough for early base purposes

Mars abhors liquid water. Those Greenland rodwells don't need to be internally pressurized, but on Mars they will need to be, and one leak ruins the well.  AFAIK such a rodwell has never been demonstrated.

PS:  If it turns out to be more convenient to recover the water as vapor, then you don't hermetically seal your rodwell bore hole.  Then the heat will sublimate the ice, and you collect the vapor from the bore hole.  But it's a lot easier to have the ice sealing your mining operation than it is the membrane.

Is it easier though??  It strikes me as the exact opposite.

We're obviously way past any experience from Greenland at this point.

[Vultur]

also, what to do in the case of a long global dust storm?

Store water ahead of time so you can turn off production for a while to save power during the worst part of the dust storm?

Global dust storms don't mean zero solar power, photovoltaic cells can use diffused light.

[BN]

also, what to do in the case of a long global dust storm?

Store water ahead of time so you can turn off production for a while to save power during the worst part of the dust storm?

Global dust storms don't mean zero solar power, photovoltaic cells can use diffused light.

what if you just landed?

if energy production is down 50% for 2-3 months, you're probably dead.

[BN]

Moving this discussion here so it's on-topic.

Sorry, I just followed the link back to your original post, not realizing it wasn't on this thread.

Rather than going point-by-point, let me try to restate my objection in a more coherent form:

Let's suppose you scrape away the overcoat of regolith, which is what keeps the ice from subliming away in the first place, and then you real quick tack down your cover.  As the ice sublimes away, the ice under the attachment point will also sublime away, undermining the attachment.

Even if you constantly re-seat the attachment, the ice just outside the attachment point will now be exposed.  Presumably, as that ice sublimes away, the regolith will slump, which will expose still more ice.  Eventually, the regolith slump will get smaller and smaller, until the rest of the ice mass self-seals.

I guess if that self-sealing process doesn't waste too much ice, you can simply move to the next area that doesn't have any slump, and continue on.

Meanwhile, let's look at what's happening at the undermined attachment point.  Unless the attachment point is constantly maintained, you'll start losing ice mass underneath it, which will limit the efficiency of the whole scheme.

If your ore is that rich, then instead of a perimeter trench you would bring in nearby sifted regolith and bury the perimeter in a mound instead. This will accomplish the same hermetic (enough) seal.

This is all much, much more complicated than a rodwell.  Rodwells in Greenland produced 38t of water per day.  That seems like more than enough for early base purposes

Mars abhors liquid water. Those Greenland rodwells don't need to be internally pressurized, but on Mars they will need to be, and one leak ruins the well.  AFAIK such a rodwell has never been demonstrated.

PS:  If it turns out to be more convenient to recover the water as vapor, then you don't hermetically seal your rodwell bore hole.  Then the heat will sublimate the ice, and you collect the vapor from the bore hole.  But it's a lot easier to have the ice sealing your mining operation than it is the membrane.

Is it easier though??  It strikes me as the exact opposite.

We're obviously way past any experience from Greenland at this point.

if we want an underground habitat (and regolith) anyway, then it would make sense to just dig up the ground (and subsurface ice) and put it in a hopper for separation/collection. at a minimum, we would not waste the water ice content of any ground we dug up.

[MickQ]

also, what to do in the case of a long global dust storm?

Store water ahead of time so you can turn off production for a while to save power during the worst part of the dust storm?

Global dust storms don't mean zero solar power, photovoltaic cells can use diffused light.

what if you just landed?

if energy production is down 50% for 2-3 months, you're probably dead.

There should be plenty of water pre supplied before landing just for this type of event.

[TheRadicalModerate]

also, what to do in the case of a long global dust storm?

Store water ahead of time so you can turn off production for a while to save power during the worst part of the dust storm?

Global dust storms don't mean zero solar power, photovoltaic cells can use diffused light.

what if you just landed?

if energy production is down 50% for 2-3 months, you're probably dead.

Sounds like an abort condition to me.