Processing/Collection of Water Ice on Mars

[BN]

Processing:

100 kg Water Ice (H2O)
Electrolysis → 11.11 kg Hydrogen (H) + 88.89 kg Oxygen (O2)
requires 555 kWh of energy

11.11 kg Hydrogen (H)
+ 61.1 kg CO2 → 22.22 kg CH4 + 49.99 kg H2O.
Sabatier Process → 44.44 kg Methane (CH4)


1 Starship Fuel/Oxidizer:
1175 tonne oxygen
325 tonne methane

8,200 MWh requiring electrolysis of 1,500 tonnes of H2O. Yields 125 tonnes excess Oxygen, 750 tonnes H2O.

If you had 100 sq meters of solar panels at 20% efficiency, at the Martian equator, it would take ~788 years to generate.

Average generation of 600-700 kW required for one Starship load of methane and oxygen in ~18 months.


[Updated 04.16.24 based on corrections by tbellman]


Collection:

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.

At one time, there was an industry of ice collection and transport across the US. I suspect the same will be true of Mars one day.


Disclaimer: Not chemist nor scientist, also bad at math. Please point out all embarrassing errors. If there is a great thread on this specific topic, my apologies, I will collect my things and go over there. Thanks.

[tbellman]

100 kg Water Ice (H2O)
Electrolysis → 11.11 kg Hydrogen (H) + 88.89 kg Oxygen (O2)
requires 366 kWh of energy

Where did you get that energy figure?  According to Wikipedia, you need 39.4 kWh/kg of generated hydrogen at 100% efficiency, and more like 50 kWh/kg in reality.  That's 555 kWh for electrolysing 100 kg water.  (And that doesn't include energy for melting the ice; but that's minor in comparison.)

11.11 kg Hydrogen (H)
 + 33.33kg Carbon (C) [derived from 122.21 kg of atmospheric CO2)
Sabatier Process → 44.44 kg Methane (CH4)
requires ~200kWh of energy (thermally complex, so wild guess)

First of all, the Sabatier reaction is not between hydrogen and carbon, but between hydrogen and carbon dioxide (CO₂), and it does not produce just methane, but methane and water.  Half of the hydrogen goes into the water.  The real reaction is 11.11 kg H₂ + 61.1 kg CO₂ → 22.22 kg CH₄ + 49.99 kg H₂O.

Second, the Sabatier reaction is exothermic.  You need to heat the inputs, but the actual reaction produces heat.

The overall process of electrolysis plus sabatier, is:
4.5 kg H₂O + 26.5 kWh electricity + 2.75 kg CO₂  →
→  0.5 kg H₂ + 4 kg O₂ + 2.75 kg CO₂  →
→  1 kg CH₄ + 4 kg O₂ + 2.25 kg H₂O

1 Starship Fuel/Oxidizer:
750 t of Methane (min 1,500,000 kg of water ice)
2,650 t of Oxygen (min 2,704,500 kg of water ice)

Those propellant figures are for the entire stack SuperHeavy + Starship.  Only the ship part will go to Mars and need refilling of propellants.

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.

And then, you seem to be under the misunderstanding that "t" means "US short ton".  It doesn't.  "t" is the metric tonne, 1000 kg.  And yes, SpaceX uses metric units.

9,899 MWh required for the Oxidizer production via electrolysis.

I'm not sure exactly how you calculated that figure.  Using the real figures (1500 t propellant load, 25 kWh/kg of produced methane for the electrolysis), I get about 8200 MWh for a full tank load of propellant, and you need to electrolyse almost 1500 tonnes of water for that.  You wold also get an excess of about 125 tonnes of oxygen.

(Note that the water you get from the Sabatier reaction is fed back to the electrolysis stage, so you only need to harvest half that amount of ice.)

If you had 100 sq meters of solar panels at 20% efficiency, at the Martian equator, it would take ~788 years to generate.

By my calculations, you will need an average of 600-700 kW of electricity to produce a full tankload of methane and oxygen in 18 months.  In practice,you need a name-plate power of maybe ten times that, to compensate for cosine-losses, nights, duststorms; and to deal with the fact that the first half of the first time you won't be operating at full efficiency.  You will definitely need tens of thousands square meters of solar panels, yes.  That is well known.

[BN]

100 kg Water Ice (H2O)
Electrolysis → 11.11 kg Hydrogen (H) + 88.89 kg Oxygen (O2)
requires 366 kWh of energy

Where did you get that energy figure?  According to Wikipedia, you need 39.4 kWh/kg of generated hydrogen at 100% efficiency, and more like 50 kWh/kg in reality.  That's 555 kWh for electrolysing 100 kg water.  (And that doesn't include energy for melting the ice; but that's minor in comparison.)

I posted this thread at 4am last night and honestly don't remember, but your estimate seems reasonable.

11.11 kg Hydrogen (H)
 + 33.33kg Carbon (C) [derived from 122.21 kg of atmospheric CO2)
Sabatier Process → 44.44 kg Methane (CH4)
requires ~200kWh of energy (thermally complex, so wild guess)

First of all, the Sabatier reaction is not between hydrogen and carbon, but between hydrogen and carbon dioxide (CO₂), and it does not produce just methane, but methane and water.  Half of the hydrogen goes into the water.  The real reaction is 11.11 kg H₂ + 61.1 kg CO₂ → 22.22 kg CH₄ + 49.99 kg H₂O.

Second, the Sabatier reaction is exothermic.  You need to heat the inputs, but the actual reaction produces heat.

The overall process of electrolysis plus sabatier, is:
4.5 kg H₂O + 26.5 kWh electricity + 2.75 kg CO₂  →
→  0.5 kg H₂ + 4 kg O₂ + 2.75 kg CO₂  →
→  1 kg CH₄ + 4 kg O₂ + 2.25 kg H₂O

My mistake, not sure why I used C here.

You're right, the reaction is exothermic, but this is happening in a very cold environment, particularly overnight, so I expect you may still need to add energy to maintain the temperature required. I suppose this would also depend on how well the process is insulated, but I am no thermal engineer.

1 Starship Fuel/Oxidizer:
750 t of Methane (min 1,500,000 kg of water ice)
2,650 t of Oxygen (min 2,704,500 kg of water ice)

Those propellant figures are for the entire stack SuperHeavy + Starship.  Only the ship part will go to Mars and need refilling of propellants.

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.

And then, you seem to be under the misunderstanding that "t" means "US short ton".  It doesn't.  "t" is the metric tonne, 1000 kg.  And yes, SpaceX uses metric units.

Good point and thank you for the units correction. Also, I suppose we are also not accounting for any boil off losses over time.

9,899 MWh required for the Oxidizer production via electrolysis.

I'm not sure exactly how you calculated that figure.  Using the real figures (1500 t propellant load, 25 kWh/kg of produced methane for the electrolysis), I get about 8200 MWh for a full tank load of propellant, and you need to electrolyse almost 1500 tonnes of water for that.  You wold also get an excess of about 125 tonnes of oxygen.

(Note that the water you get from the Sabatier reaction is fed back to the electrolysis stage, so you only need to harvest half that amount of ice.)

Agree. Also, good point about the water reuse, that is significant.

If you had 100 sq meters of solar panels at 20% efficiency, at the Martian equator, it would take ~788 years to generate.

By my calculations, you will need an average of 600-700 kW of electricity to produce a full tankload of methane and oxygen in 18 months.  In practice,you need a name-plate power of maybe ten times that, to compensate for cosine-losses, nights, duststorms; and to deal with the fact that the first half of the first time you won't be operating at full efficiency.  You will definitely need tens of thousands square meters of solar panels, yes.  That is well known.

Dust accumulation on that kind of surface area would be a chore over time. Might require some kind of solar panel roomba to keep up.

Appreciate your input and I think I agree on all points. I will modify the OP with revised figures as they are refined in this thread. Hoping we can form a good ballpark reference for water ice resource utilization here.

[Twark_Main]

The nice thing is, on Mars insulation is easy. You just put MLI in a bag and pull a very slight slight vacuum, and you can have R-200 per inch. 

For solar panels the "roomba" is a grid of 3-4 sets of wires, which are alternately shorted to high voltage in a "chasing lights" sequence. This electrostatically sweeps dust off the panels.

https://spectrum.ieee.org/tech-from-mars-selfcleaning-solar-panels

[tbellman]

The nice thing is, on Mars insulation is easy. You just put MLI in a bag and pull a very slight slight vacuum, and you can have R-200 per inch. 

Unfortunately, that's a problem for the Sabatier reactor, not a feature.  It typically needs cooling in order to not overheat, not isolation to keep it warm...

The heat produced by the Sabatier reaction is nice, in that you can use that to heat the inputs (the hydrogen and the carbon dioxide) to a suitable temperature.  But that heat tends to be more than you need for heating the inputs, so you need to cool away the excess.

And then you need to chill the output, in order to separate the water from the methane.

And then you need to further chill the methane to make it liquid.  (And likewise the oxygen from the electrolysation step.)

(The thin and cold atmosphere is helpful in then keeping the methane and oxygen liquid, though, as isolating your tank farms becomes easier.)

(Here is one NASA design study about Sabatier reactors on Mars that I found with a quick web search.  PDF attached.  I have only had time to skim it, though, not read it thoroughly.)

[deadman1204]

How do you fuel a starship? That takes ALOT of people and equipment on Earth to do.
Astronaut with a ladder is not a soluation either.

[BN]

The nice thing is, on Mars insulation is easy. You just put MLI in a bag and pull a very slight slight vacuum, and you can have R-200 per inch. 

Unfortunately, that's a problem for the Sabatier reactor, not a feature.  It typically needs cooling in order to not overheat, not isolation to keep it warm...

The heat produced by the Sabatier reaction is nice, in that you can use that to heat the inputs (the hydrogen and the carbon dioxide) to a suitable temperature.  But that heat tends to be more than you need for heating the inputs, so you need to cool away the excess.

And then you need to chill the output, in order to separate the water from the methane.

And then you need to further chill the methane to make it liquid.  (And likewise the oxygen from the electrolysation step.)

(The thin and cold atmosphere is helpful in then keeping the methane and oxygen liquid, though, as isolating your tank farms becomes easier.)

(Here is one NASA design study about Sabatier reactors on Mars that I found with a quick web search.  PDF attached.  I have only had time to skim it, though, not read it thoroughly.)

So we would need a constant supply of CO2 and Hydrogen to sustain the reaction and avoid requiring heat input. In return, our heating bill would be much lower. It seems like that would make more sense than stopping and restarting the reactor and the output would just be chilled as we use it for heating the habitat or a greenhouse at night.

Electrolysis would be running constantly, as would ice collection operations and each step of the ice/gas resource collection and processing would ideally be automated in a single integrated system.

For solar panels the "roomba" is a grid of 3-4 sets of wires, which are alternately shorted to high voltage in a "chasing lights" sequence. This electrostatically sweeps dust off the panels.

https://spectrum.ieee.org/tech-from-mars-selfcleaning-solar-panels

"Mazumder said that within two minutes, the process removes about 90 percent of the dust deposited on a solar panel and requires only a small amount of the electricity generated by the panel for cleaning operations."

This was published 14 years ago. Is there any video or demonstration of this working on Earth?

How do you fuel a starship? That takes ALOT of people and equipment on Earth to do.
Astronaut with a ladder is not a soluation either.

I think a lot of that is the launch window and managing cryogenic fuel, pressure, temperatures and fill level.

Leaving Mars, methane would not ignite without an oxidizer, probably the fuel would not be cryogenic and the launch window would be pretty long. I don't think it would need to be as complex as most orbital launches from Earth and the Starship return variant design would likely be adapted to the Mars situation.

[Twark_Main]

The nice thing is, on Mars insulation is easy. You just put MLI in a bag and pull a very slight slight vacuum, and you can have R-200 per inch. 

Unfortunately, that's a problem for the Sabatier reactor, not a feature.  It typically needs cooling

Sure, but I don't see how "on Mars insulation is easy" is causing the problem.

Obviously if you don't need insulation, you don't install insulation.   

[BN]

Elon stated in a recent interview that they are probably landing at Arcadia Planitia.

So if we don't have automated subsurface ice harvesting, the base will certainly fail. There is no readily available, high purity exposed above-surface ice within range.


Does anyone know what this hardware looks like? It should probably be tested during the Mars mission launching next year.

Map of sites within AP and ice content chart

https://www.nasa.gov/wp-content/uploads/2015/11/viola_arcadiaplanitia_final_tagged.pdf?emrc=85d42a

[Vultur]

Elon stated in a recent interview that they are probably landing at Arcadia Planitia.

So if we don't have automated subsurface ice harvesting, the base will certainly fail. There is no readily available, high purity exposed above-surface ice within range.


Does anyone know what this hardware looks like? It should probably be tested during the Mars mission launching next year.

Map of sites within AP and ice content chart

https://www.nasa.gov/wp-content/uploads/2015/11/viola_arcadiaplanitia_final_tagged.pdf?emrc=85d42a

Ice harvesting will not necessarily be complete automated; i don't think return propellant gets made until the first humans get there (though the *hardware* to do so will be landed during the preceding cargo-only synod).

I don't think it's realistic for the 2026 synod to be that cargo-only synod. Even if Starship is interplanetary capable by Nov-Dec 2026 (which is fairly aggressive, as orbital refueling has to work first and that is only 18-19 months away) I doubt they'd be able to do more than test cruise to Mars and EDL at Mars.

[BN]

Ice harvesting will not necessarily be complete automated; i don't think return propellant gets made until the first humans get there (though the *hardware* to do so will be landed during the preceding cargo-only synod).

I don't think it's realistic for the 2026 synod to be that cargo-only synod. Even if Starship is interplanetary capable by Nov-Dec 2026 (which is fairly aggressive, as orbital refueling has to work first and that is only 18-19 months away) I doubt they'd be able to do more than test cruise to Mars and EDL at Mars.

what is it that humans would need to do that machines/tesla bot cannot do for propellant production?

[Vultur]

Ice harvesting will not necessarily be complete automated; i don't think return propellant gets made until the first humans get there (though the *hardware* to do so will be landed during the preceding cargo-only synod).

I don't think it's realistic for the 2026 synod to be that cargo-only synod. Even if Starship is interplanetary capable by Nov-Dec 2026 (which is fairly aggressive, as orbital refueling has to work first and that is only 18-19 months away) I doubt they'd be able to do more than test cruise to Mars and EDL at Mars.

what is it that humans would need to do that machines/tesla bot cannot do for propellant production?

There's a big difference between running machines real time, with access for maintenance, vs running machines with 20 minute light lag and no ability to do maintenance.

The actual harvesting would be done by machines but I'd expect humans to be heavily involved. Mars rovers move very slow, InSight had difficulties drilling, etc.; real time control would allow "industrial" operations.

[BN]

what kind of machine are you imagining? if we're just digging regolith and putting it in a hopper for separation, that can all be automated. for example NASA's RASSOR can operate autonomously.

if we're using an auger with a vacuum, there's no reason for human involvement. if there's a problem hopefully a tesla bot can reposition/reset/repair, etc

[Twark_Main]

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...

[spacenut]

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.   

[Twark_Main]

Would [a small nuclear reactor] not be easier than a huge amount of solar panels?

If cost is a proxy for "ease," then no it is not easier. 

[Slarty1080]

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.

It would be expensive as it will require a lot of development, but IMO some form of fairly large scale nuclear plant will be required on Mars if we are ever to develop more than a "flags and foot prints" presence there. Power availability will throttle development of any surface infrastructure as it will be needed in vast quantities for ISRU production of most materials from oxygen and propellants to plastic, glass, steel and aluminum. It will also be needed to power the basic functioning of the base from vehicles and life support to heating and lighting.

[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

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?

my concept:

phase 1
1. augur vacuum begins drilling
2. friction heat → localized sublimation → water vapor → condensation hopper

phase 2
1. shovel high purity regolith into a tank
2. transportation to separation hopper

phase 3
1. open pit mining of korolev ice blocks

[tbellman]

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

The Kilopower project seems to have ended in 2018, after they tested their 1 kW_e prototype "KRUSTY".  No larger reactors, nor any non-prototype reactors, were developed as far as I know.  The latest plans from NASA for nuclear reactors is the Fission Surface Power, where they will attempt to buy reactors commercially.  So no, not "already developed".

As for the reactor at Camp Century, or more generally the Army Nuclear Power Program, none of the reactors designed and built were made for operation in Mars-like conditions (near vacuum, with no or extremely little air or water available for cooling).  It was also more than 50 years ago; any designs from then are not practically useful (without significant further development) today.

[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

The Kilopower project seems to have ended in 2018, after they tested their 1 kW_e prototype "KRUSTY".  No larger reactors, nor any non-prototype reactors, were developed as far as I know.  The latest plans from NASA for nuclear reactors is the Fission Surface Power, where they will attempt to buy reactors commercially.  So no, not "already developed".

As for the reactor at Camp Century, or more generally the Army Nuclear Power Program, none of the reactors designed and built were made for operation in Mars-like conditions (near vacuum, with no or extremely little air or water available for cooling).  It was also more than 50 years ago; any designs from then are not practically useful (without significant further development) today.

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

[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.

[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.

Sounds like an abort condition to me.

I don't think the first few crews sent will have the option to return to Earth right away.

even in the event of a global dust storm for 3 months, they will need to be able to collect ice, produce energy, grow food and survive.


the storms seem to occur every ~7 years during southern summer, so depending on the timing, they may be less of an immediate concern.

[TheRadicalModerate]

Sounds like an abort condition to me.

I don't think the first few crews sent will have the option to return to Earth right away.

even in the event of a global dust storm for 3 months, they will need to be able to collect ice, produce energy, grow food and survive.

the storms seem to occur every ~7 years during southern summer, so depending on the timing, they may be less of an immediate concern.

Sure they will, especially if it's a NASA-sanctioned mission.  It's catastrophically bad PR to kill a crew, especially on a foreseeable contingency.

With a Block 3 Starship, you can load out enough prop to get back to LMO, where there can be a depot waiting to refuel the Ship with enough prop to make it back through an opposition-class return to Earth.

And it doesn't have to be a complete abort.  You just convert the mission to short stay.  You can still get plenty of science and test data out of a short-stay mission.

[Robotbeat]

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.

No, you’re not. It takes almost no energy to keep crew alive. Vast majority of energy is for ascent propellant, and that matters over a 2 year average, so 2-3 months doesn’t matter really.

People forget that the entire biosphere of Earth runs on solar power as well, and stores energy chemically for winter or whatever. Absolutely no difference here, except photovoltaics are far less sensitive to temperature extremes and, unlike photosynthesis, produce some power in all seasons.

Some of you seem incredibly unable to think from first principles. It’s a mystery how some of you would have survived what all of our ancestors had to do.

[Robotbeat]

Sounds like an abort condition to me.

I don't think the first few crews sent will have the option to return to Earth right away.

even in the event of a global dust storm for 3 months, they will need to be able to collect ice, produce energy, grow food and survive.

the storms seem to occur every ~7 years during southern summer, so depending on the timing, they may be less of an immediate concern.

Sure they will, especially if it's a NASA-sanctioned mission.  It's catastrophically bad PR to kill a crew, especially on a foreseeable contingency.

With a Block 3 Starship, you can load out enough prop to get back to LMO, where there can be a depot waiting to refuel the Ship with enough prop to make it back through an opposition-class return to Earth.

And it doesn't have to be a complete abort.  You just convert the mission to short stay.  You can still get plenty of science and test data out of a short-stay mission.

Aborting to orbit is a really bad idea. Orbit is far more dangerous, higher radiation dose? Etc. Way better to do as BN suggests and stay for another synod.

[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.

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.

Yeah. You would want plenty of extra water anyway

(I actually think ice mining would be more for ISRU purposes, that would require enormously more water than crew drinking water, especially since the latter can be largely recycled.)

[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.

No, you’re not. It takes almost no energy to keep crew alive. Vast majority of energy is for ascent propellant, and that matters over a 2 year average, so 2-3 months doesn’t matter really.

People forget that the entire biosphere of Earth runs on solar power as well, and stores energy chemically for winter or whatever. Absolutely no difference here, except photovoltaics are far less sensitive to temperature extremes and, unlike photosynthesis, produce some power in all seasons.

Some of you seem incredibly unable to think from first principles. It’s a mystery how some of you would have survived what all of our ancestors had to do.

pointing out that plants use sunlight isn't galaxy-brain first principles material. my statement is contingent on the reserve energy available to the crew.

so how much energy is this "almost no energy" required to keep crew alive? enlighten me.

[TheRadicalModerate]

Aborting to orbit is a really bad idea. Orbit is far more dangerous, higher radiation dose? Etc. Way better to do as BN suggests and stay for another synod.

I'm not talking about aborting to orbit.  I'm talking about aborting to Earth.  There are going to be lots of contingencies that require short stay.

[Robotbeat]

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.

No, you’re not. It takes almost no energy to keep crew alive. Vast majority of energy is for ascent propellant, and that matters over a 2 year average, so 2-3 months doesn’t matter really.

People forget that the entire biosphere of Earth runs on solar power as well, and stores energy chemically for winter or whatever. Absolutely no difference here, except photovoltaics are far less sensitive to temperature extremes and, unlike photosynthesis, produce some power in all seasons.

Some of you seem incredibly unable to think from first principles. It’s a mystery how some of you would have survived what all of our ancestors had to do.

pointing out that plants use sunlight isn't galaxy-brain first principles material. my statement is contingent on the reserve energy available to the crew.

so how much energy is this "almost no energy" required to keep crew alive? enlighten me.

Their own body heat is sufficient if the hab is large (so enough buffer for oxygen and CO2) and they have food an water and the hab is well-insulated. Zero, in other words, for a week.

Humans use about 1kg of O2 per day and exhale about the same amount of CO2 (some food energy is oxidized as H2O), so if your hab is 120m^2 per person, you have about 12 days of survivable oxygen if at Earth-like oxygen and pressure. But CO2 is more of the limit there, as beyond 5% for extended periods there are major mental confusion problems, or around 7 days.


But if you operate at reduced pressure and Apollo like atmosphere, you can keep the CO2 levels reasonable just by bleeding in some O2 gas, in which case you need like 10-20kg of O2 per day per person. The 1000 tons of O2 needed for a Starship will keep a crew of 10 alive for like 5000 days (maybe 2500 days to keep the CO2 levels more reasonable). Crew metabolism is enough to warm that to usable temperature (from Martian ambient temperatures) if the hab is well-insulated. In other words, natural boiloff provides plenty of oxygen.

It also doesn’t take THAT much energy to run basic regenerative CO2 scrubbers like Orion uses, which allows you to be a lot more economical.

But there will be plenty of power available anyway. A crewed hab is usually budgeted for around 10kW, and Starship needs about 1MW average power to make fuel, so if your solar arrays get reduced to just 2% of their usual output for a few months (an absurdly low number), you still have twice as much power as you need for the crewed hab.

[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.

No, you’re not. It takes almost no energy to keep crew alive. Vast majority of energy is for ascent propellant, and that matters over a 2 year average, so 2-3 months doesn’t matter really.

People forget that the entire biosphere of Earth runs on solar power as well, and stores energy chemically for winter or whatever. Absolutely no difference here, except photovoltaics are far less sensitive to temperature extremes and, unlike photosynthesis, produce some power in all seasons.

Some of you seem incredibly unable to think from first principles. It’s a mystery how some of you would have survived what all of our ancestors had to do.

pointing out that plants use sunlight isn't galaxy-brain first principles material. my statement is contingent on the reserve energy available to the crew.

so how much energy is this "almost no energy" required to keep crew alive? enlighten me.

Their own body heat is sufficient if the hab is large (so enough buffer for oxygen and CO2) and they have food an water and the hab is well-insulated. Zero, in other words, for a week.

Humans use about 1kg of O2 per day and exhale about the same amount of CO2 (some food energy is oxidized as H2O), so if your hab is 120m^2 per person, you have about 12 days of survivable oxygen if at Earth-like oxygen and pressure. But CO2 is more of the limit there, as beyond 5% for extended periods there are major mental confusion problems, or around 7 days.


But if you operate at reduced pressure and Apollo like atmosphere, you can keep the CO2 levels reasonable just by bleeding in some O2 gas, in which case you need like 10-20kg of O2 per day per person. The 1000 tons of O2 needed for a Starship will keep a crew of 10 alive for like 5000 days (maybe 2500 days to keep the CO2 levels more reasonable). Crew metabolism is enough to warm that to usable temperature (from Martian ambient temperatures) if the hab is well-insulated. In other words, natural boiloff provides plenty of oxygen.

It also doesn’t take THAT much energy to run basic regenerative CO2 scrubbers like Orion uses, which allows you to be a lot more economical.

But there will be plenty of power available anyway. A crewed hab is usually budgeted for around 10kW, and Starship needs about 1MW average power to make fuel, so if your solar arrays get reduced to just 2% of their usual output for a few months (an absurdly low number), you still have twice as much power as you need for the crewed hab.

so your solution is 12km by 12km in solar panels? how much in solar do you think is required for 1MW avg power?

[Robotbeat]

Maybe try calculating it accurately? This is, after all, the same plan as SpaceX has had for over a decade, now. I feel like you should be beyond making mistakes by factors of a couple thousand.

[Vultur]

12 km^2 for 1 MW would imply power generation of 1/12 watt per square meter. That doesn't seem remotely plausible, by a couple orders of magnitude.

Mars gets a bit less than half the insolation Earth does, not thousands of times less.

[Robotbeat]

12 km^2 for 1 MW would imply power generation of 1/12 watt per square meter. That doesn't seem remotely plausible, by a couple orders of magnitude.

Mars gets a bit less than half the insolation Earth does, not thousands of times less.

By over 3 orders of magnitude.

[BN]

12 km^2 for 1 MW would imply power generation of 1/12 watt per square meter. That doesn't seem remotely plausible, by a couple orders of magnitude.

Mars gets a bit less than half the insolation Earth does, not thousands of times less.

By over 3 orders of magnitude.

I did make an error somewhere there, my apologies. Why don't you give your real-world estimate for required solar power in area? There will be many operations such as ice collection, growing food, etc which need to occur in parallel to propellent production.

I think the energy requirements for the habitat are much higher than the "almost no energy" you are suggesting due to your assumptions about thermal being too optimistic, especially for the initial settlement.

[Vultur]

12 km^2 for 1 MW would imply power generation of 1/12 watt per square meter. That doesn't seem remotely plausible, by a couple orders of magnitude.

Mars gets a bit less than half the insolation Earth does, not thousands of times less.

By over 3 orders of magnitude.

I did make an error somewhere there, my apologies. Why don't you give your real-world estimate for required solar power in area?

I would suggest something on the rough order of 1 hectare (10,000 square meters) per megawatt "nameplate power".

Real world conditions (using batteries to average out high and low/no generation times) maybe 4x the area? So 40,000 m^2 per megawatt.

25% capacity factor would be really good for pure solar on Earth I think, but outside of dust storms, Mars is far less cloudy than Earth. Unlike, say, the US Southwest you don't have a monsoon season soaking up some of the best summer early-afternoon sun.

We could do better than 25% panel efficiency, but we also need lots of area, so the absolute peak performance might not be the right thing to chase here).

So I think that's fairly conservative*, and it's still hundreds of times better.

*more aggressively, we could go with advanced triple junction cells for maybe 35% efficiency, and a lower estimate of loss to imperfect atmospheric opacity... We could get something like 160-180 W/m^2 nameplate capacity.

[Robotbeat]

I assume 20% efficiency, 20% capacity factor, and light intensity 40% of the 1000W/m^2 assumed for noon at earth. These are all fairly conservative (space rated solar cells can get 30-35% efficiency but they’re expensive…), but close enough. So about 16W_average/m^2, so you need 62500m^2 for 1MW average, or a square 250m on a side. But the area matters less than the mass.

Your original post here used 600-700kW average as the estimate. That, combined with tracking solar panels and high efficiency cells, you can halve that total area.

Although tracking typically benefits from being spread out more, so the actual array footprint will be small but the whole area will be larger.

Anyway: 250m square on a side is a decent estimate.

[BN]

I assume 20% efficiency, 20% capacity factor, and light intensity 40% of the 1000W/m^2 assumed for noon at earth. These are all fairly conservative (space rated solar cells can get 30-35% efficiency but they’re expensive…), but close enough. So about 16W_average/m^2, so you need 62500m^2 for 1MW average, or a square 250m on a side. But the area matters less than the mass.

Your original post here used 600-700kW average as the estimate. That, combined with tracking solar panels and high efficiency cells, you can halve that total area.

Although tracking typically benefits from being spread out more, so the actual array footprint will be small but the whole area will be larger.

Anyway: 250m square on a side is a decent estimate.

we need to use average efficiency, considering dust which tends to stick to panels. unless they are constantly being cleaned, which would cost energy in some form, they will have a significantly reduced average efficiency. insight lander's power was reduced by 80% after a few months and most vehicles have a lifetime average efficiency below 8%. a large area of panels will be difficult to keep clean all the time, and whatever the cleaning process is will only remove some of the dust, not all of it. I agree that mass is a significant constraint, which may preclude tracking. furthermore, we need to consider the latitude, and winter season, which reduce output. tracking would require maintenance, lubrication, structure and dust mitigation.

while clouds are minimal on mars, the sky is not always clear and sometimes it's dusty without it necessarily being a dust storm. if you look at pictures from mars often visibility of the horizon is worse than it is on earth, reducing solar incidence. the diurnal swings of 80C will also likely impact efficiency, degrading over time. there will also be transfer losses and potentially some inverter losses. some panels will break. it seems to me that we need significantly more solar power in the real world than what most people are coming up with on paper.

I think we will be closer to 5-12% real-world average efficiency, and should actually take a production capacity assuming even lower than that to be safe. there are no unaccounted for external factors which increase real world generation, but many factors which decrease it, some of which may not be properly accounted for.

[Vultur]

we need to use average efficiency, considering dust which tends to stick to panels. unless they are constantly being cleaned, which would cost energy in some form, they will have a significantly reduced average efficiency.

MER's experience is rather better than that. With decent placement and even very minimal maintenance, I think dust on panels will have little meaningful effect.

whatever the cleaning process is will only remove some of the dust, not all of it.

Technically true, but close enough to all of it. MER natural cleaning events (wind when rovers were in a favorable location) got pretty close to 100% clean. .. like 96% I think.

while clouds are minimal on mars, the sky is not always clear and sometimes it's dusty without it necessarily being a dust storm.

Yeah that's already figured in ... A perfectly clear atmosphere would give something like 148 W/m^2 for 25% efficient panels (solar constant at 1.52 AU is about 590 W/m^2), not the 100 I was saying. That's already assuming significant loss.

if you look at pictures from mars often visibility of the horizon is worse than it is on earth, reducing solar incidence. the diurnal swings of 80C will also likely impact efficiency, degrading over time.

When the sun is on the horizon itself insolation is pretty low even on Earth, so that won't matter much.

ISS solar arrays suffer way worse temperature swings.

I assume 20% efficiency, 20% capacity factor, and light intensity 40% of the 1000W/m^2 assumed for noon at earth. These are all fairly conservative (space rated solar cells can get 30-35% efficiency but they’re expensive…), but close enough. So about 16W_average/m^2, so you need 62500m^2 for 1MW average, or a square 250m on a side. But the area matters less than the mass.

Yeah, that strikes me as fairly conservative but reasonable. 40000 m^2 versus 62500 m^2 per MW isn't worth arguing about, what latitude they end up at will probably make at least that much difference.

And yeah, mass is more important. Thinner panels with lower efficiency= more area needed probably win out if they mass less. Land is cheap on Mars, and I really don't think maintenance of panels will prove to be that big of a deal.

I wouldn't bother with tracking, too much mass.

Your original post here used 600-700kW average as the estimate.

Yeah life support power for a small initial crew (before we get to major farming on Mars etc) should be waaayyyy less than that.

[Robotbeat]

Tracking may be useful for the single reason that it’s also a great way to minimize and mitigate dust.

[BN]

we need to use average efficiency, considering dust which tends to stick to panels. unless they are constantly being cleaned, which would cost energy in some form, they will have a significantly reduced average efficiency.

MER's experience is rather better than that. With decent placement and even very minimal maintenance, I think dust on panels will have little meaningful effect.

I don't think MER is a good analog, Insight is probably a better reference for "cleaning events" since it is stationary. it would probably make sense to look at the specific dust characteristics in the Arcadia Planitia region, both in terms of the qualities of the dust itself and the characteristics of the wind patterns. wind force and frequency is regionally variable, as it is on earth.

Tracking may be useful for the single reason that it’s also a great way to minimize and mitigate dust.

that is a significant mass increase, may even 5x total mass. or more, given that there are very light solar panel solutions now. the efficiency benefit of tracking would have to be enormous. on the other hand, flat panels low to the ground which never tilt could lose 80% power generation within a few months without intervention. if dust is somehow not really an issue, as Vultur is suggesting, then tilting definitely is not worth it, but I've never heard that take before.

[Twark_Main]

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.

I don't think the first few crews sent will have the option to return to Earth right away.

even in the event of a global dust storm for 3 months, they will need to be able to collect ice, produce energy, grow food and survive.


the storms seem to occur every ~7 years during southern summer, so depending on the timing, they may be less of an immediate concern.

We might try this technique called "looking at a calendar."   

We know the Mars dust storm season. We know the Mars arrival windows.  Just make sure the first human landing doesn't take place when those two line up. Fortunately you only have to do that once.

We have a name for the alternative competing philosophy: Go Fever.

Are the most probable arrival windows for the first crew during dust storm season? Or are we pumping billions into "necessary" nukes for nothing? 

[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.

Sounds like an abort condition to me.

I don't think the first few crews sent will have the option to return to Earth right away.

even in the event of a global dust storm for 3 months, they will need to be able to collect ice, produce energy, grow food and survive.


the storms seem to occur every ~7 years during southern summer, so depending on the timing, they may be less of an immediate concern.

This is solved via a breakthrough Sumerian technique called "looking at a calendar."

We know the Mars dust storm season. We know the Mars transit windows.  All you need to do is make sure the first human landing doesn't take place when those two things line up.

Did anyone check whether the most probable windows for the first crew actually arrive during dust storm season? Or are we pumping billions into "necessary" nukes for nothing? 

practically, we will utilize all hohmann transfer windows, regardless of the increased probability of a dust storm. it doesn't make sense to wait another 26 months, so we will just have to send additional generation capacity to compensate. having extra energy production (after the dust storm subsides) is not a bad thing anyway.

while the 2026 window is likely very dusty, 2028, 2030 are less so. the global dust storms occur during northern hemisphere fall/winter, although they are more intense the further south your latitude is. this is complicated by the elliptical orbit of mars partly driving the seasons, which is different than earth. in any case, how this will actually affect power generation will depend on the actual qualities of the dust itself and the specific region we land in.

[Vultur]

we need to use average efficiency, considering dust which tends to stick to panels. unless they are constantly being cleaned, which would cost energy in some form, they will have a significantly reduced average efficiency.

MER's experience is rather better than that. With decent placement and even very minimal maintenance, I think dust on panels will have little meaningful effect.

I don't think MER is a good analog, Insight is probably a better reference for "cleaning events" since it is stationary.

InSight's location was not chosen for good solar power production, though.

that is a significant mass increase, may even 5x total mass. or more, given that there are very light solar panel solutions now. the efficiency benefit of tracking would have to be enormous.

Yeah.

if dust is somehow not really an issue, as Vultur is suggesting, then tilting definitely is not worth it, but I've never heard that take before.

To quote myself from the Mars power thread 11 years ago:

Apparently, solar panels should be put on a hill top, and they will remain pretty clean.

MER Update by A.J.S Rayl for Sols 3650-3680
http://www.planetary.org/explore/space-topics/space-missions/mer-updates/2014/05-mer-update-opportunity-hunts-ancient-clays.html

"Perfectly clean solar arrays would boast a dust factor of 1.0, so the larger the dust factor, the cleaner the arrays, and the more sunlight is transformed into power. The rover's power production and the Tau and the dust factor all fluctuate throughout a given month, but in May Opportunity's solar array dust factor went from 0.832 to 0.962, which is close to as good as it can get and a record for a rover more than 10 years into its mission.

...

"We've spent a lot of time thinking what's the magic formula – what is the approach you take to getting a rover clean?" mused Squyres. "The answer is: you climb a hill. Pure and simple. We saw this with Spirit too, where the big cleaning events came at the summit of Husband Hill, the ridge crest. This is the first mountaineering we've done with Opportunity and we climb to the top of the Murray Ridge and – ka-boom! So the magic formula is -- climb a hill, get up on a ridge crest that exposes you to the winds and you get cleaned off. We've seen it on both sides of the planet now."

So it may be possible just to choose a settlement site near a hill and put the solar farm on its slope! Flat land is probably bad.

[Robotbeat]

The rovers were fairly low to the ground and their solar panels were in the worst possible orientation for dust accumulation. A single axis tracker should improve on all of these while still being pretty lightweight. They can be bifacial, too.

Oh, interesting thing I learned about ISS’s original solar panels: they are bifacial. Doesn’t really help much, but that was interesting to me.

[Twark_Main]

"They should have sent....    a meteorologist!"


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