Processing/Collection of Water Ice on Mars

[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?