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Thread: Mars Colony: Soylent Green?

  1. #1 Mars Colony: Soylent Green? 
    Forum Cosmic Wizard icewendigo's Avatar
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    So, Im just wondering, would people go apeshit if on a Mars Colony, dead people were recycled into organic nutrient for hydroponics?
    (or for use in a Biodome nature small woodland park )


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    If they did, then we could also use the apeshit.


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    eat me
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    It takes really desperate situations for people to put aside their superstitions for more practical matters.
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    Quote Originally Posted by Lynx_Fox View Post
    It takes really desperate situations for people to put aside their superstitions for more practical matters.

    I am afraid I do not grasp that statement.
    Is it possible to explain it?
    Last edited by Cogito Ergo Sum; August 22nd, 2013 at 04:25 PM. Reason: Grammatical error.
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

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    Quote Originally Posted by icewendigo View Post
    So, Im just wondering, would people go apeshit if on a Mars Colony, dead people were recycled into organic nutrient for hydroponics?
    (or for use in a Biodome nature small woodland park )
    That's what we do now. Trees grow in graveyards.
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    I imagine the type of people willing to move to Mars would be fairly pragmatic types who would be able to accept composting the human deceased via alkaline hydrolysis for use as fertilizer.
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    Biosphere 2 - Wikipedia, the free encyclopedia

    I wonder if we will try for a longer biosphere project with more people before actually dumping people on Mars to fend for themselves?

    I also wonder how many of those people that have signed up for a one way trip to Mars would volunteer as a biosphere participant?

    I realize there is a big difference between being stranded on Mars and stuck in a dome here on Earth. But if we can't make the dome thing here on Earth work why would we expect people to survive on Mars?
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    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by Lynx_Fox View Post
    It takes really desperate situations for people to put aside their superstitions for more practical matters.

    I am afraid I do not grasp that statement.
    Is it possible to explain it?
    I'd assume he means that although using human remains as fertiliser would be a very sensible and efficient use of resources, some people would feel very uncomfortable about sprinkling their loved ones over the vegetable patch. I think that's what Lynx meant, maybe not.

    I'm not sure I'd agree entirely. Mars colonists will likely be more practical-minded and keenly aware of the value of raw materials and how nutrient cycles operate. Recycling colonists will likely be viewed as common sense - at least in the early phases of Martian settlement.
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    Forum Cosmic Wizard icewendigo's Avatar
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    Indeed in all likelihood, the more pragmatic people would be there(most probably all the details of the changes to lifestyle would be known factors before anyone went there), and for all the things one would sacrifice to go there, it might be the silver lining, presumably you would go for the people and society being built.


    "But if we can't make the dome thing here on Earth work why would we expect people to survive on Mars?"
    I agree that the first step should be to make biodome prototypes/testing-grounds that are pleasant to live in here, where various social organization models/prototypes can be experimented with, so that an eventual Mars colony has a greater chance of being a place where the colonist are able to function smoothly and live a happy life.
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    Quote Originally Posted by Bad Robot View Post
    But if we can't make the dome thing here on Earth work why would we expect people to survive on Mars?
    More incentive on Mars.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by Bad Robot View Post
    But if we can't make the dome thing here on Earth work why would we expect people to survive on Mars?
    More incentive on Mars.
    Yes there is that. If you don't make it work you die. Here on Earth you just leave the dome. But we could make it more real here on Earth. If you leave the dome before the test is complete you will be shot dead no exceptions.
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    Quote Originally Posted by Bad Robot View Post
    Yes there is that. If you don't make it work you die. Here on Earth you just leave the dome. But we could make it more real here on Earth. If you leave the dome before the test is complete you will be shot dead no exceptions.
    Or just put the biodome inside a much larger sphere that contains Martian atmosphere. Then tell people they are free to leave if they want . . .
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    Quote Originally Posted by Zwirko View Post
    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by Lynx_Fox View Post
    It takes really desperate situations for people to put aside their superstitions for more practical matters.

    I am afraid I do not grasp that statement.
    Is it possible to explain it?
    I'd assume he means that although using human remains as fertiliser would be a very sensible and efficient use of resources, some people would feel very uncomfortable about sprinkling their loved ones over the vegetable patch. I think that's what Lynx meant, maybe not.

    I'm not sure I'd agree entirely. Mars colonists will likely be more practical-minded and keenly aware of the value of raw materials and how nutrient cycles operate. Recycling colonists will likely be viewed as common sense - at least in the early phases of Martian settlement.

    Thank you for your explanation!

    I do think that Mars colonists should be informed about this (if they have not thought about the necessity of using human remains as fertilizer) before they head to the red planet.
    In all honestly, using a human corpse in order to grow food is more useful than putting it into a coffin (especially on Mars).

    Quote Originally Posted by billvon View Post
    Quote Originally Posted by Bad Robot View Post
    Yes there is that. If you don't make it work you die. Here on Earth you just leave the dome. But we could make it more real here on Earth. If you leave the dome before the test is complete you will be shot dead no exceptions.
    Or just put the biodome inside a much larger sphere that contains Martian atmosphere. Then tell people they are free to leave if they want . . .

    Yo Dawg, I herd you like spheres, so I put an sphere in your sphere so you can dome while you dome.
    Last edited by Cogito Ergo Sum; August 23rd, 2013 at 04:20 PM. Reason: Grammatical error.
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

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    "using a human corpse in order to grow food is a much more useful than putting it into a coffin"
    Yes I agree. If I was a colonist, I would want my cells/molecules to be put to optimal use, like extracting some tissue that could have lab value (experiment, testing, cells for making cartilage, keep a dna sample for bio-anthropological reference, whatever), and then use the rest in the agricultural recycling process.

    Instead of tombstone, a page on the colony intranet website with a list of my favourite art/media (books, movies, music, etc) in case someone's curious
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    I've told my parents that if I died, I wanted to be cremated, mixed with the soil, and have a fruit tree planted in the ash-soil. Then I could feed the hungry even after I died.
    My mom thought I was gross.
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    Quote Originally Posted by TheUnknowable View Post
    I've told my parents that if I died, I wanted to be cremated, mixed with the soil, and have a fruit tree planted in the ash-soil. Then I could feed the hungry even after I died.
    My mom thought I was gross.

    To be honest, I think that your idea is beautiful and certainly not sickening or gross.
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    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    Quote Originally Posted by TheUnknowable View Post
    I've told my parents that if I died, I wanted to be cremated, mixed with the soil, and have a fruit tree planted in the ash-soil. Then I could feed the hungry even after I died.
    My mom thought I was gross.
    I don't think that's gross at all. I actually find embalming and sealing in a concrete grave liner pretty gross; I don't want my remains to be removed from the cycle of life, I want them to return to the earth so my nutrients may nourish other life.
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    Quote Originally Posted by Zwirko View Post
    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by Lynx_Fox View Post
    It takes really desperate situations for people to put aside their superstitions for more practical matters.

    I am afraid I do not grasp that statement.
    Is it possible to explain it?
    I'd assume he means that although using human remains as fertiliser would be a very sensible and efficient use of resources, some people would feel very uncomfortable about sprinkling their loved ones over the vegetable patch. I think that's what Lynx meant, maybe not.
    Yes uncomfortable for religious reasons.
    --
    I also wonder how many of those people that have signed up for a one way trip to Mars would volunteer as a biosphere participant?

    I would have signed up for either. The difference, as others have said, the biosphere you just leave if the greeny idiologs are driving you crazy, or their experiment fails--on Mars those idiologs priorities would not be prioritized above practical engineering and science.
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    I think they would need an oxygen recycling chemical reaction they can put heat or electricity into to process the air. Then the biodomes would just need to make food at first, and you wouldn't have to have as much to survive at first.
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    Quote Originally Posted by TheUnknowable View Post
    I think they would need an oxygen recycling chemical reaction they can put heat or electricity into to process the air. Then the biodomes would just need to make food at first, and you wouldn't have to have as much to survive at first.

    Should we not contemplate about how we get to Mars first?
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by TheUnknowable View Post
    I think they would need an oxygen recycling chemical reaction they can put heat or electricity into to process the air. Then the biodomes would just need to make food at first, and you wouldn't have to have as much to survive at first.

    Should we not contemplate about how we get to Mars first?
    Have you looked at this topic yet?

    The 123,000 MPH Plasma Engine That Could Finally Take Astronauts To Mars

    I think this might be a good way to get to Mars.
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    Quote Originally Posted by Bad Robot View Post
    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by TheUnknowable View Post
    I think they would need an oxygen recycling chemical reaction they can put heat or electricity into to process the air. Then the biodomes would just need to make food at first, and you wouldn't have to have as much to survive at first.

    Should we not contemplate about how we get to Mars first?
    Have you looked at this topic yet?

    The 123,000 MPH Plasma Engine That Could Finally Take Astronauts To Mars

    I think this might be a good way to get to Mars.

    I second that.
    Thank you for the article!
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by TheUnknowable View Post
    I think they would need an oxygen recycling chemical reaction they can put heat or electricity into to process the air. Then the biodomes would just need to make food at first, and you wouldn't have to have as much to survive at first.

    Should we not contemplate about how we get to Mars first?
    I'm putting my money on Elon Musk to figure that part out

    Elon Musk's mission to Mars | Technology | The Guardian
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    More into recycling, more frugal and less tolerant of pollution than the most extreme environmentalists I suspect. Yet I think that Mars colony proposals tend to attract people who are looking for resource rich frontiers without limits so, unless the real thing attracts a more pragmatic and realistic crew, some illusions will arrive there firmly implanted. They may have no problems recycling bodies via compost but I doubt that it would extend to eating the dead. Unless things went very badly. In which case they could lose Earthside backing - which I don't think they will be able to last long without.

    But I'm not convinced any self-sustaining or self-perpetuating space colonies will happen except after a long history as part of - and dependent on - a sustainable economy based on Earth.
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    Problem with the composting idea. The first agriculture on Mars would have to be hydroponic for efficiency. Compost is not useable in hydroponics. The cremation plus processing of ash would be better.
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    Quote Originally Posted by skeptic View Post
    Problem with the composting idea. The first agriculture on Mars would have to be hydroponic for efficiency. Compost is not useable in hydroponics.
    No, but it's much, much easier than hydroponics.

    Hydroponics is a great technology when you have stockpiles of the required nutrients. When you don't have those stockpiles - but you do have poop and garbage - composting becomes more effective.

    The cremation plus processing of ash would be better.
    Too many useful organics lost.
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    Billvon

    Your point is valid, but the thing about hydroponics is area in use. An early colony on Mars would simply not have the space, many, many acres, under cover with air to do traditional soil gardening. They would need the most space efficient agriculture possible, and that is hydroponics. Hydroponics also requires the lowest weight in nutrients of any agricultural method, due to its high efficiency. Any attempt at colonisation will need food to be grown, and that means carrying fertiliser. But the bulk of fertiliser needed at first, meaning needed to be carried, is least with hydroponics. Hydroponics needs lots of water and CO2, but those two things are abundant on Mars.

    Now I admit that recycling nutrients is probably easier with soil based agriculture, but that would not be practical in the early stages of a colony. Reclaiming nutrients from ash after flash incinerating a human body (or human feces and urine) is something that is entirely feasible using modern technology. Sooner or later, getting essential minerals from Mars resources will be vital. The phosphorus, nitrogen compounds, and potassium in particular brought from Earth will only last so long, regardless of which agricultural method is used.
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    Quote Originally Posted by skeptic View Post
    Sooner or later, getting essential minerals from Mars resources will be vital. The phosphorus, nitrogen compounds, and potassium in particular brought from Earth will only last so long, regardless of which agricultural method is used.
    I agree with that. Do you know if any of our exploring has detected any of those elements that could be easily mined? I can't believe anybody would go on a one way trip without knowing they will have a reliable food supply. Can we list colonist needs in order of importance.

    1. Breathable air with O2 being critical.
    2. Drinkable water
    3. Food
    4. Protection from the harsh environment (very cold, not much atmosphere and high radiation).
    5. Ability to maintain 1 thru 4 indefinitely.

    Human bodies do contain elements that will be needed, so ways of recycling them will be needed, whatever that will entail.
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    Quote Originally Posted by skeptic View Post
    Your point is valid, but the thing about hydroponics is area in use. An early colony on Mars would simply not have the space, many, many acres, under cover with air to do traditional soil gardening.
    ?? I think the one thing they WOULD have is space! Cover an area with an inflatable dome, inflate it with Martian air (mostly CO2) fill it with treated Martian regolith, add plants, water and compost and let them grow. Initially you have to add a little oxygen (plants need it just like we do) but since they break down CO2 to oxygen, after the first crop you'll have to _remove_ oxygen to keep the pressure under control.

    Martian atmosphere is around .4% of the pressure of ours; in other words, about .06psi. If you had to fill the dome with Earth-pressure air it would be hard to create a strong enough dome to survive that force. But plants can grow in much lower pressures - lettuce has been tested down to about 1psi. So the tent does not have to be nearly as strong; it could be a fairly thick sheet of Mylar attached to a strong base. Since surface temperatures during the day on Mars can reach 70F, and since even average temperatures are around 0F, the greenhouse effect of the dome will likely keep plants warm enough to grow during the day. At night you would either have to cover the domes or heat them.

    Alternatively you might choose to pressurize them to about 2psi. This would allow people to work in shirtsleeves inside them with nothing more than an oxygen mask, thus providing additional working/storage space and making it easier to harvest crops. Higher pressures would allow people to work inside them without masks - and of course the plant's ability to generate oxygen would greatly reduce the need for stored/manufactured oxygen and CO2 scrubbing.

    To inflate them initially just compress the CO2 from Martian atmosphere and use that. You'd need to supply enough oxygen to keep the plants alive at first (about 50% in a very low pressure atmosphere) but since the pressure is so low to begin with that's not a lot of O2. Once the plants start growing you'd have to slowly release air (too much O2) and pump in more CO2. Fortunately on Mars it's free.

    To create dirt you can just 'wash' Martian regolith with water. The regolith is saturated with superoxides and thus will bubble and hiss, releasing oxygen. (You can use this O2 to supply the first atmosphere for the dome.) You then neutralize the pH and you have basic dirt, a substrate that can support roots and has some of the basic nutrients - potassium and magnesium. It does not have nitrogen, phosphorous or potassium, so those will have to be added - and compost will be the easiest way to do that. (And of course some dirt will have to be imported from Earth to provide the soil bacteria and insects that healthy soil needs.)

    The good thing about this system is that once the first greenhouse is established it makes the next ones that much easier to set up. You have a lot more soil to provide starter cultures for your next greenhouses, and once the system of food -> people -> compost is established it is largely self sustaining.

    Carrying all the hydroponic nutrients required for hydroponic farming is doable but requires a lot more mass taken from Earth to Mars. I would suggest that replacing all those hydroponic nutrients with actual food (and transparent tents) would do several things:

    1) Provide more time to get farming set up before food became critical
    2) Provide the compost (via feces, urine and food waste) to start the soil creation process
    3) Result in a longer term source of food.
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    Sorry, 'composting' to mean breaking down by some organic method to retain the precious biological materials. Minced up into vats to become liquid nutrients more likely than a gardener's compost heap. I do think those materials - and the oxygen - are going to be too valuable to 'burn'. Most of the recovery of nutrients would have to be from the flue gases rather than ash - which seems overly energy and equipment intensive.


    But - would there be enough sunlight on Mars under a dome for efficient plant growth? Efficient agriculture and most productive crops requires full sun equivalent lighting. Also Mars doesn't have the atmosphere or magnetosphere to protect from cosmic radiation. I would expect underground and under lights would be the starting point and those are even more energy and equipment intensive. Nuclear power required - and Mars is unlikely to have accessible nuclear fuels anywhere near the surface; Earth's ores are a result of (relatively) recent concentration (and natural enrichment that results) by hydro-geothermal processes.
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    Quote Originally Posted by Ken Fabos View Post
    But - would there be enough sunlight on Mars under a dome for efficient plant growth? Efficient agriculture and most productive crops requires full sun equivalent lighting.
    Sunlight varies from between 50% and 70% of what we get on Earth. You'd see some slowdown in production - but a speedup from the higher CO2 concentrations.

    Also Mars doesn't have the atmosphere or magnetosphere to protect from cosmic radiation.
    While radiation is significantly higher it's not much of a problem for crops. A suited human could live on the surface of Mars for three years without hitting the NASA limit for radiation exposure - and crops will be on the surface a much shorter time. You might get more disease from radiation exposure but we're talking an increase of a few percent.
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    Agriculture under a dome on Mars would not be easy. There needs to be intensive energy input. Both to increase temperature to that which is optimal for plant growth, and to add light. Sunlight lamps will be required. I am not sure how well insulated such a dome could be, but heat loss would be a major consideration. Add a lot of insulation and light from the sun will be seriously reduced. I am not sure I believe that there is over 50% of Earth's solar intensity anyway. The inverse square law says no.

    Radiation levels at Mars surface are high enough that the colonists will not want to spend more than a few hours per day exposed. Meaning they will spend most of their time underground. I am inclined to think that the optimal solution would be to have hydroponics underground with nuclear energy for heating and lighting.
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    Quote Originally Posted by skeptic View Post
    Agriculture under a dome on Mars would not be easy. There needs to be intensive energy input. Both to increase temperature to that which is optimal for plant growth, and to add light. Sunlight lamps will be required. I am not sure how well insulated such a dome could be, but heat loss would be a major consideration. Add a lot of insulation and light from the sun will be seriously reduced. I am not sure I believe that there is over 50% of Earth's solar intensity anyway. The inverse square law says no.

    Radiation levels at Mars surface are high enough that the colonists will not want to spend more than a few hours per day exposed. Meaning they will spend most of their time underground. I am inclined to think that the optimal solution would be to have hydroponics underground with nuclear energy for heating and lighting.
    You could be right about that and it would be good to know before we start dumping people off to fend for themselves.
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    Skeptic, I think Billvon has the numbers right for solar intensity; it's more than I'd thought, mostly because of the lack of atmosphere and cloud on Mars. Not so sure how things would go during periods of global dust storms, such as Mars endures. Even if lighting isn't necessary there will be need for heating.

    I think it would be a major undertaking to build and colonise by dome or underground here on Earth - even with air ready to breathe and condense water out of, with oil powered earthmoving machinery, concrete, steel etc as needed. Doing so on Mars has to be a lot harder.

    This kind of colonising is like nothing in human history - a history that began with small groups carrying all they required with them, all essential knowledge contained within a few individuals. More recent colonisation experience was most often into the territories of existing human populations - which were as subject to raiding as to trading to provide what the colonists needed to last until more ships arrived. Fresh water could be expected to be present. Game was present. Fertile soils, with sunshine and rain laid on were present. And there was a Mother country, which a colony was the extension of, to become the market for what a colony could produce and the source of all it couldn't. The high technological requirements for colonising places where none of these exist make for a very high minimum threshold for skills, equipment and supplies. The capacity for making and replacing high tech equipment looks like something only a large and diverse economy can manage. The capacity for ongoing R&D and high tech innovation is something only a very large, diverse and prosperous economy can manage.
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    Quote Originally Posted by skeptic View Post
    I am not sure I believe that there is over 50% of Earth's solar intensity anyway. The inverse square law says no.
    Insolation at Earth orbit: 1360 w/m^2 avg
    Insolation at Earth surface due to atmospheric attenuation: ~1000 w/m^2

    Insolation at Mars orbit: 600 w/m^2 avg
    Insolation at Mars surface due to atmospheric attenuation: ~590 w/m^2

    I am inclined to think that the optimal solution would be to have hydroponics underground with nuclear energy for heating and lighting.
    Photosynthesis is not all that efficient (a few percent.) The only reason it's so useful to us is that sunlight is free. If you need to generate power from a reactor (30-40% efficiency) then use lamps (25% efficiency) then count on photosynthesis (2-3%) you are going to need a huge power plant with all the associated problems of moving a huge power plant to Mars. If you have the power it's going to be a lot more efficient to synthesize sugars and proteins directly.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by skeptic View Post
    I am not sure I believe that there is over 50% of Earth's solar intensity anyway. The inverse square law says no.
    Insolation at Earth orbit: 1360 w/m^2 avg
    Insolation at Earth surface due to atmospheric attenuation: ~1000 w/m^2

    Insolation at Mars orbit: 600 w/m^2 avg
    Insolation at Mars surface due to atmospheric attenuation: ~590 w/m^2

    I am inclined to think that the optimal solution would be to have hydroponics underground with nuclear energy for heating and lighting.
    Photosynthesis is not all that efficient (a few percent.) The only reason it's so useful to us is that sunlight is free. If you need to generate power from a reactor (30-40% efficiency) then use lamps (25% efficiency) then count on photosynthesis (2-3%) you are going to need a huge power plant with all the associated problems of moving a huge power plant to Mars. If you have the power it's going to be a lot more efficient to synthesize sugars and proteins directly.
    Synthetic neutrients would make more sense, but can you make them pure enough for ingestion? It kind of goes along with my "synthetic plant" idea for producing oxygen.
    If you had to grow things, I'd look into Aquaponics. You use compost to grow duckweed, which you feed to fish, which fertilize the plants. With UV sterilization, you could probably make it work with human waste and pureed astronaut too. Also, it uses far less water because it doesn't drain away, though if your dome is a giant terrarium with no drainage, that wouldn't matter. The more efficient use of space might, though, because you'd need smaller domes.
    I would think the colony would use a solar powered satellite to "beam" them power via microwave. It could have panels a square km in size, producing 360 MW at 60% efficiency (which they have now in CPV cells) That's far more than they would need. They would have to have a good bit of power storage (I'm thinking hydrogen fuel cells or liquid salt) to handle the storms (and night if we didn't carry three and make a loop around the planet), but it would be practically free with no fuel needed, just initial equipment.
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    Quote Originally Posted by TheUnknowable View Post
    Synthetic neutrients would make more sense, but can you make them pure enough for ingestion? It kind of goes along with my "synthetic plant" idea for producing oxygen.
    If you had to grow things, I'd look into Aquaponics. You use compost to grow duckweed, which you feed to fish, which fertilize the plants. With UV sterilization, you could probably make it work with human waste and pureed astronaut too. Also, it uses far less water because it doesn't drain away, though if your dome is a giant terrarium with no drainage, that wouldn't matter. The more efficient use of space might, though, because you'd need smaller domes.
    I would think the colony would use a solar powered satellite to "beam" them power via microwave. It could have panels a square km in size, producing 360 MW at 60% efficiency (which they have now in CPV cells) That's far more than they would need. They would have to have a good bit of power storage (I'm thinking hydrogen fuel cells or liquid salt) to handle the storms (and night if we didn't carry three and make a loop around the planet), but it would be practically free with no fuel needed, just initial equipment.
    Those dust storms you mentioned, sometimes last for up to a year or more. I'd want a little better than a short term energy storage system, and it looks like we are up for that challenge.

    Toshiba Builds 100x Smaller Micro Nuclear Reactor

    Toshiba has developed a new class of micro size Nuclear Reactors that is designed to power individual apartment buildings or city blocks. The new reactor, which is only 20 feet by 6 feet, could change everything for small remote communities, small businesses or even a group of neighbors who are fed up with the power companies and want more control over their energy needs.

    The 200 kilowatt Toshiba designed reactor is engineered to be fail-safe and totally automatic and will not overheat. Unlike traditional nuclear reactors the new micro reactor uses no control rods to initiate the reaction. The new revolutionary technology uses reservoirs of liquid lithium-6, an isotope that is effective at absorbing neutrons. The Lithium-6 reservoirs are connected to a vertical tube that fits into the reactor core. The whole whole process is self sustaining and can last for up to 40 years, producing electricity for only 5 cents per kilowatt hour, about half the cost of grid energy.

    Toshiba expects to install the first reactor in Japan in 2008 and to begin marketing the new system in Europe and America in 2009.
    Toshiba Builds 100x Smaller Micro Nuclear Reactor
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    Quote Originally Posted by TheUnknowable View Post
    Synthetic neutrients would make more sense, but can you make them pure enough for ingestion?
    Sure! The problem isn't making them pure enough; it's making them _impure_ enough. We need hundreds of compounds in trace amounts to be healthy, and carbohydrate synthesis is much better at making a few simple carbohydrates. At best you could come up with all the calories you needed.

    If you had to grow things, I'd look into Aquaponics. You use compost to grow duckweed, which you feed to fish, which fertilize the plants. With UV sterilization, you could probably make it work with human waste and pureed astronaut too. Also, it uses far less water because it doesn't drain away, though if your dome is a giant terrarium with no drainage, that wouldn't matter. The more efficient use of space might, though, because you'd need smaller domes.
    Well, light drives everything in that cycle as well so you'd still need a large amount of sun exposure. You'd also need to maintain significantly higher pressures so the animals survive.

    I would think the colony would use a solar powered satellite to "beam" them power via microwave.
    Sure, although I would think you'd want to prove that out here on Earth first. (And it's probably a few decades away.)

    It could have panels a square km in size, producing 360 MW at 60% efficiency (which they have now in CPV cells)
    Modern practical cells are around 20% efficient. The best multijunction space rated cells (hideously expensive) are around 35% efficient. Then add the efficiencies of the magnetrons, antennas, transmission paths and receivers and you have a pretty low overall efficiency. In general because of the thinner atmosphere of Mars, and the lack of significant weather*, you'd be doing pretty well just having solar panels on the ground.

    (* - dust storms may be an exception)
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    I would rather have both hydroponics and soil compost. Maybe soil compost can be used to grow insects to be eaten or be used for derivative/alternate purposes (storage/methane/something-something)?

    If robots could build underground galleries in advance(or there were caves) and that you had underground real estate as a given from the start,
    could you have solar panels to power lamps in underground agriculture galleries to reduce the need for heating?

    Here s a small digging robot http://www.redorbit.com/news/video/s...mars-02262013/
    Last edited by icewendigo; August 26th, 2013 at 02:55 PM.
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    Quote Originally Posted by icewendigo View Post
    I would rather have both hydroponics and soil compost. Maybe soil compost can be used to grow insects to be eaten or be used for derivative/alternate purposes (storage/methane/something-something)?
    Short term and for small bases you could probably get hydroponics to give you some supplemental food, but for larger bases/longer term you're going to need crops under sun, fed compost. That's the only easy way to close the cycle. (And of course we have a lot more experience with it.)

    could you have solar panels to power lamps in underground agriculture galleries to reduce the need for heating?
    Well, solar panels are around 20% efficient, good LED lamps are around 15% efficient. That's an end to end efficiency of around 3%. Greenhouse glass, even triple paned, passes about 90% of the light that hits it.

    In terms of heat, scientists have built working greenhouses in Nunavut, Canada where it gets down to -40C. This is warmer than Mars but is effectively a bigger challenge to heat, since our much thicker atmosphere conducts heat a lot better.
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    That's an end to end efficiency of around 3%.

    Does that mean you need 100m of solar panel to provide the light for 3m of hydoponics? Thats surprizing.


    In terms of heat, scientists have built working greenhouses in Nunavut, Canada where it gets down to -40C. This is warmer than Mars but is effectively a bigger challenge to heat, since our much thicker atmosphere conducts heat a lot better.
    Interesting. What are they using to heat it in the winter?


    What about radiation shielding do plants need protection equivalent to being underground?
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    Er, I think it simply means that energy output is only 3% of energy of energy input.
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    On energy.
    Any Mars colony will need lots of energy to succeed. It will need to roast rock to get water. To compress atmosphere for CO2. To use electric arc furnaces to get minerals from Mars dust. Electrolysis. Heat. Lighting. etc. etc.

    Solar cells will be weak at Mars surface, and probably impractical with such an enormous demand. Solar cells in orbit would be better, but there are many control difficulties there. Nuclear power, though, carried the energy density required in a relatively small space. The reference to the Toshiba reactor is good. However, it is not the only microreactor under development. The travelling wave reactor, due out in 2020, will also be tiny, and innately 'safe'. The TWR has the advantage that it runs on uranium 238, which is probably accessible on Mars, without the enormous level of technology required to process uranium 235 for other reactors.. It is worth noting that the entire Cassini misson to Saturn is run off a small nuclear reactor, which is way less efficient than the two more modern ones mentioned above.

    In establishing a largely self sufficient Mars colony, a nuclear reactor will almost certainly be one of the first things delivered.
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    Quote Originally Posted by icewendigo View Post
    Does that mean you need 100m of solar panel to provide the light for 3m of hydoponics? Thats surprizing.


    If you want the same intensity of light - yes.


    Interesting. What are they using to heat it in the winter?
    Solar and wind power, but mostly direct solar heat from sun capture. The system determines when the best time to plant is based on available sunlight and times its plantings accordingly. (It's all automated.)

    What about radiation shielding do plants need protection equivalent to being underground?
    The surface radiation of Mars is not sufficient to kill plants in the time that they are growing crops. For more protection, glass works pretty well.
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    Quote Originally Posted by skeptic View Post
    The reference to the Toshiba reactor is good. However, it is not the only microreactor under development.
    Agreed, although currently any nuclear reactor (even tiny 200kW ones) are far too heavy to be practically transported to Mars. There would need to be a lot of work done to miniaturize it enough - AND make it reliable/safe enough for virtually unattended use.

    It is worth noting that the entire Cassini misson to Saturn is run off a small nuclear reactor, which is way less efficient than the two more modern ones mentioned above.
    Note that Cassini uses an RTG rather than a reactor. It has a small power output (300 watts) since it is not a reactor; it just relies on decay heat from isotopes.
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    Small correction to billvon's post. Glass does not stop the damaging radiation on Mars. The biggest problem is cosmic radiation, not ultraviolet. Cosmic radiation is stopped by hydrogen atoms, meaning a thick layer of water ice will do it, or any material with lots of hydrogen. Ultraviolet is stopped by glass, but that is not the problem at the surface of Mars. Probably the best barrier to cosmic radiation on Mars surface would be a few metres of rock. ie. live underground.

    Note that the level of cosmic radiation on Mars surface is still a lot less than it is in space, so our colonists can still spend a few hours each day on the surface without more than a small increase in cancer risk.
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    Quote Originally Posted by skeptic View Post
    Small correction to billvon's post. Glass does not stop the damaging radiation on Mars. The biggest problem is cosmic radiation, not ultraviolet. Cosmic radiation is stopped by hydrogen atoms, meaning a thick layer of water ice will do it, or any material with lots of hydrogen. Ultraviolet is stopped by glass, but that is not the problem at the surface of Mars. Probably the best barrier to cosmic radiation on Mars surface would be a few metres of rock. ie. live underground.

    Note that the level of cosmic radiation on Mars surface is still a lot less than it is in space, so our colonists can still spend a few hours each day on the surface without more than a small increase in cancer risk.
    Mars does not have any magnetic field around it, so all those sun storms and mass ejections will be very damaging to anything not shielded when they happen.
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    Quote Originally Posted by Bad Robot View Post
    Mars does not have any magnetic field around it, so all those sun storms and mass ejections will be very damaging to anything not shielded when they happen.
    Keep in mind that Venus has no magnetic field, and yet solar storms are not damaging to things on the surface. That's due to the thickness of the Venusian atmosphere. The atmosphere on Mars is not all that thick but still provides a significant level of protection against solar wind. (You would MUCH rather be on the surface of Mars than orbiting Mars in your spacecraft during bad solar weather.)
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by TheUnknowable View Post
    Synthetic neutrients would make more sense, but can you make them pure enough for ingestion?
    Sure! The problem isn't making them pure enough; it's making them _impure_ enough. We need hundreds of compounds in trace amounts to be healthy, and carbohydrate synthesis is much better at making a few simple carbohydrates. At best you could come up with all the calories you needed.

    If you had to grow things, I'd look into Aquaponics. You use compost to grow duckweed, which you feed to fish, which fertilize the plants. With UV sterilization, you could probably make it work with human waste and pureed astronaut too. Also, it uses far less water because it doesn't drain away, though if your dome is a giant terrarium with no drainage, that wouldn't matter. The more efficient use of space might, though, because you'd need smaller domes.
    Well, light drives everything in that cycle as well so you'd still need a large amount of sun exposure. You'd also need to maintain significantly higher pressures so the animals survive.

    I would think the colony would use a solar powered satellite to "beam" them power via microwave.
    Sure, although I would think you'd want to prove that out here on Earth first. (And it's probably a few decades away.)

    It could have panels a square km in size, producing 360 MW at 60% efficiency (which they have now in CPV cells)
    Modern practical cells are around 20% efficient. The best multijunction space rated cells (hideously expensive) are around 35% efficient. Then add the efficiencies of the magnetrons, antennas, transmission paths and receivers and you have a pretty low overall efficiency. In general because of the thinner atmosphere of Mars, and the lack of significant weather*, you'd be doing pretty well just having solar panels on the ground.

    (* - dust storms may be an exception)
    1) I was worried about toxins and harmful proteins in the food.
    2) Artificial lights would be a must. Also, fish shouldn't need high pressure, just water oxygenation (because the water cycling might not add enough) and warm temperatures.
    3) true. We'd need to work it out. There is a wireless power transfer system available, but it only works over a few meters.
    4) I saw a company that had created a 60% efficient sell, but even if I was wrong, the point is that efficiency doesn't matter. Wasted energy heats the atmosphere, releasing more CO2, increasing atmo pressure, etc. And I believe microwaves are largely unaffected by dust storms. You may need to conserve power a bit, but that's it.
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    Quote Originally Posted by TheUnknowable View Post
    2) Artificial lights would be a must. Also, fish shouldn't need high pressure, just water oxygenation (because the water cycling might not add enough) and warm temperatures.
    Why wouldn't fish need pressure? They need a reasonable ppO2 like any other animal.

    4) I saw a company that had created a 60% efficient sell, but even if I was wrong, the point is that efficiency doesn't matter.
    It definitely matters when it comes to cost and weight. If it requires 20 square meters of panel to light 1 square meter of plants, that's not that practical a solution. I haven't seen any demonstrated efficiencies over about 45% - and those are hideously expensive and impractical.

    Wasted energy heats the atmosphere, releasing more CO2, increasing atmo pressure, etc.
    A few kilowatts won't do a thing to the totality of Mars.
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    If you had to fill the dome with Earth-pressure air it would be hard to create a strong enough dome to survive that force.
    haven't finished the whole threads but...is this right? i can put 130psi into a plastic soft drink bottle to make a water rocket here on earth with no problems. that is pretty thin plastic.

    also if you use the sabatier reaction you would just need to take some hydrogen with you and from that and carbon dioxide you can make water, and from that oxygen by electrolysis and methane for fuel. this fuel could be used for rockets or heating the domes.

    Sabatier reaction - Wikipedia, the free encyclopedia
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by TheUnknowable View Post
    2) Artificial lights would be a must. Also, fish shouldn't need high pressure, just water oxygenation (because the water cycling might not add enough) and warm temperatures.
    Why wouldn't fish need pressure? They need a reasonable ppO2 like any other animal.

    4) I saw a company that had created a 60% efficient sell, but even if I was wrong, the point is that efficiency doesn't matter.
    It definitely matters when it comes to cost and weight. If it requires 20 square meters of panel to light 1 square meter of plants, that's not that practical a solution. I haven't seen any demonstrated efficiencies over about 45% - and those are hideously expensive and impractical.

    Wasted energy heats the atmosphere, releasing more CO2, increasing atmo pressure, etc.
    A few kilowatts won't do a thing to the totality of Mars.
    1) I suppose they'd need it to keep the O2 from leaving the water, but wouldn't a few PSI be enough if you bubbled enough oxygen through it? We're talking about Catfish. They live under hundreds of feet of water sometimes. They're very hardy.
    Catfish: Water Quality
    Catfish need only 3-4mg/L
    DO Saturation Table - DNR
    At 15 degrees c (59 degrees F), the water is saturated at 10.07 mg/L. That's 2.5 to 3.3 times as much, so if the water remained saturated, the atmospheric pressure could go fairly low.

    2) You would need much more surface space for standard agriculture. Also, those panels are printed on mylar, so they're 5mm or less thick, and can be folded to save space. That might make them more space (and weight) efficient than a nuclear reactor, plus, no fuel is required. Also, the expense of sending the panels to Mars will be far greater than the cost of the panels, so the cost doesn't really matter.

    3) A few hundred megawatts, not a few KW, but maybe it won't be enough. We could always point two of the three microwave beams at the north pole.
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    Either way, we are talking novel technology. No one has used the space solar cell collection and microwaves beaming down for energy. Not has anyone used the micro-nuclear reactors like the travelling wave reactor. I guess both are possibilities, but both will need to be thoroughly tested close to home to ensure there are no bugs.
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    Quote Originally Posted by TheUnknowable View Post
    1) I suppose they'd need it to keep the O2 from leaving the water, but wouldn't a few PSI be enough if you bubbled enough oxygen through it? We're talking about Catfish. They live under hundreds of feet of water sometimes.
    Right - but depth INCREASES the ppO2. You'd have to maintain enough pressure in the water to keep up whatever level of ppO2 they would need.

    From your table below they need about 1/3 of what normal water provides. Which would be 5psi at normal O2 concentrations. If you put pure O2 in the water you could get it down to 2psi or so, but that's still a lot more than you need for plants.

    Also there's a larger problem. For every pound of meat you get from an animal you have to provide ~10 pounds of feed. You are much better off growing things that people can eat directly; it's a 10 to 1 advantage. (To put it another way, if you need 1 acre of farm to make enough for you to eat, you'd need 10 acres to provide enough catfish food.)

    You would need much more surface space for standard agriculture.
    Agreed! And that's the good part - surface space is free; you just have to tent it. (And folded tents are a lot easier to deal with than solar panels, frames, converters, wiring, lamps etc etc,)

    Also, those panels are printed on mylar, so they're 5mm or less thick, and can be folded to save space.
    Oh, you're taking organic (non crystalline) cells. Now you are down in the 8% efficiency range. That's several times worse.

    Also, the expense of sending the panels to Mars will be far greater than the cost of the panels, so the cost doesn't really matter.
    We're talking hundreds of millions of dollars for a large array of those cells, so yes - it definitely matters! You would likely choose less efficient but cheaper panels.

    A few hundred megawatts, not a few KW, but maybe it won't be enough. We could always point two of the three microwave beams at the north pole.
    Again, if you have the technology/money to do that, build a big mirror and point it at the north pole. WAY cheaper.
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    Question: How big is this Mars colony we've been talking about? You can live without food animals with a few tons of protein powder for a very long time, and damn the cravings for meat. It's for sure that shipments from Earth will have to continue until the colony could survive on it's own. But I've heard no estimates as to how many years that might take. Does anybody know?
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    Quote Originally Posted by Bad Robot View Post
    Question: How big is this Mars colony we've been talking about?
    Ranges I have heard have been from four (Zubrin's smaller Mars Direct mission) to a hundred (the Kim Stanley Robinson version of Mars colonization. Fictional but well thought out.) Naturally it would grow with time.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by Bad Robot View Post
    Question: How big is this Mars colony we've been talking about?
    Ranges I have heard have been from four (Zubrin's smaller Mars Direct mission) to a hundred (the Kim Stanley Robinson version of Mars colonization. Fictional but well thought out.) Naturally it would grow with time.
    Personally I would never consider 4 to be a colony, but I could see 100 getting close to small colony status.
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    I think the best approach will be to use relatively the simplest technology that gets the job done. For example rather than using artificial light and heat, to simulate the conditions of earth, we select plants that do well in cool, partially shaded environments such as peas, carrots, spinach and some bean varieties. And of those crops you can select to take advantage of the very long growing season on Mars.

    When I think colony, I think about several thousand, don't think any less can really get to even a low level of autonomy necessary to survive.
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    Quote Originally Posted by Lynx_Fox View Post
    When I think colony, I think about several thousand, don't think any less can really get to even a low level of autonomy necessary to survive.
    Most serious proposals I've seen start small, so that if you have a catastrophic problem early on, you can halt the next wave before they are stranded on a planet that can't support them.
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    Realistically, you are not going to escape the need to provide heat and light. Mars is just too damn cold. Even using a heated dome to grow crops, you will need lots of energy. The dome itself would have to be multiply insulated, meaning that a lot of the sun's light will simply not penetrate, and artificial light will need to be added. In spite of that insulation, a lot of heat will escape anyway, meaning a lot of heat will need to be added on a regular basis.

    Bearing in mind the need to spend most of colonist time undergeround, to avoid harmful radiation, why not just dig deep caves and insulate them, and add sunlight lamps, and grow crops close to the living area?
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    Quote Originally Posted by skeptic View Post
    Bearing in mind the need to spend most of colonist time undergeround, to avoid harmful radiation, why not just dig deep caves and insulate them, and add sunlight lamps, and grow crops close to the living area?
    Because then you need 20x the area of solar panels to drive the sunlight lamps. You have to ship these from Earth, and they are expensive and heavy. Any long term plan for colonization cannot rely on underground farms with artificial light.
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    Size: It might start with robots preparing the initial outpost phase, with a preliminary outpost of lets say 4-8 colonists to setup the initial phase of the colony as payloads are received before more colonists arrive, and eventually, if Elon Musk is able to build quickly reusable (near Airbus airplane-like reusability) I think he estimates that several thousand colonists could eventually be sent each year, so that you would get something like a 80,000 person colony. Musk and SpaceX are focusing on getting people and payloads there, other people need to focus on how things work once your there.

    Energy:
    What are the various ways to harness energy that could use the local environment as much as possible and minimize the payload?

    Can panels take advantage of the thin atmosphere, can they harness cosmic radiation or UV light?

    Can solar panels, mirrors or glass for green houses be manufactured on Mars? (assuming you have a small nuclear reactor or that solar panels can provide the energy to build other solar panels)


    Can plants/microbes/fungus/insects convert Martian soil and air into organic matter and/or methane? (So that methane combustion can be used as an auxiliary power source)
    Like you might have a dome made with martian soil that is sealed and with a given environment, bring an amount of soil/air in the environment, have the bacteria process the soil, and then extract the organic matter/methane out of the dome and replace it with new martian soil?
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    Quote Originally Posted by Bad Robot View Post
    Quote Originally Posted by billvon View Post
    Quote Originally Posted by Bad Robot View Post
    Question: How big is this Mars colony we've been talking about?
    Ranges I have heard have been from four (Zubrin's smaller Mars Direct mission) to a hundred (the Kim Stanley Robinson version of Mars colonization. Fictional but well thought out.) Naturally it would grow with time.
    Personally I would never consider 4 to be a colony, but I could see 100 getting close to small colony status.
    Mars One is planning on sending four people every two years, starting in 2023.
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    Quote Originally Posted by icewendigo View Post
    What are the various ways to harness energy that could use the local environment as much as possible and minimize the payload?
    Solar is about it. Wind speeds are high but the thin atmosphere means that very little energy can be harvested. Fortunately solar output is close to what we are used to on Earth. (Farther from the Sun but less atmosphere/clouds.)

    Can panels take advantage of the thin atmosphere, can they harness cosmic radiation or UV light?
    Cosmic radiation - energy density there is very low (far less than 1 watt/sq m)
    UV light - maybe although
    1) there isn't much energy there (<70 w/sq m)
    2) there are no materials we know of that have a bandgap at that energy so you can't really harness the energy

    Can solar panels, mirrors or glass for green houses be manufactured on Mars? (assuming you have a small nuclear reactor or that solar panels can provide the energy to build other solar panels)
    Glass is not too hard. Soda lime glass has a long history and can be made from a variety of minerals. Solar-PV panels are a lot harder and would require a lot of infrastructure.

    Can plants/microbes/fungus/insects convert Martian soil and air into organic matter and/or methane?
    Well, as you know plants can convert CO2 to starches and sugars and they can be fermented into alcohol or digested to methane.
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    "Well, as you know plants can convert CO2 to starches and sugars and they can be fermented into alcohol or digested to methane."


    Are there advantages (redundancy/diversity-in-available-types-of-matter, etc) to using plants as a source of methane, as an auxiliary method to the industrial-ish method that might be contemplated to produce rocket fuel?

    (If methane can be produced for rocket fuel, Im guessing it would be a good idea to have auxiliary generators that work on methane?)
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    I am still very cynical about the idea of using solar panels for energy. I do not think those who suggest this 'solution' appreciate just how much energy will be required. To get all power direct from the sun will require literally square miles of solar panels.

    By the time any colony is ready to be started on Mars, mini nuclear reactors will be available, and they will be able to supply almost unlimited energy.

    For example, very powerful electric arc furnaces will be needed to melt Mars rocks and dust, to extract metals and other minerals. The residual melted rock can be blasted with compressed Mars atmosphere to turn it into rock foam for insulation. Without this kind of high energy technology, the Mars colonists will be dependent on Earth supplies, and that is not practical. Initially such technologies will be supplied in small scale, with output in the area of kilograms at a time, rather than tonnes. But in time, multi-tonne outputs will be needed. And that means enormous energy generation.

    I suspect that, within a decade or two, the colonists will be able to smelt a wide range of metals, including uranium 238. Since this can be used as fuel in a travelling wave reactor, that is likely to be the long term source of electricity.

    The whole thing will be some time in the future, and the technologies available will be much more sophisticated than anything we have today. For example, robots should be available. Robot diggers might well be the key to developing extensive underground habitat. More advanced 3D printers might be able to use the metals as raw material that the electric arc smelters produce. With raw materials produced by electric arc smelters, and 3D printers, a wide range of very complex materials cold be manufactured on site by the Mars colonists. I know that we, on Earth, will quickly get tired of spending a trillon dollars plus per year to send supplies and equipment to a tiny number of Mars colonists.
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    Quote Originally Posted by icewendigo View Post
    (If methane can be produced for rocket fuel, Im guessing it would be a good idea to have auxiliary generators that work on methane?)
    Well, you also need oxygen; that has to be produced as well. So you have both problems there.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by TheUnknowable View Post
    1) I suppose they'd need it to keep the O2 from leaving the water, but wouldn't a few PSI be enough if you bubbled enough oxygen through it? We're talking about Catfish. They live under hundreds of feet of water sometimes.
    Right - but depth INCREASES the ppO2. You'd have to maintain enough pressure in the water to keep up whatever level of ppO2 they would need.

    From your table below they need about 1/3 of what normal water provides. Which would be 5psi at normal O2 concentrations. If you put pure O2 in the water you could get it down to 2psi or so, but that's still a lot more than you need for plants.

    Also there's a larger problem. For every pound of meat you get from an animal you have to provide ~10 pounds of feed. You are much better off growing things that people can eat directly; it's a 10 to 1 advantage. (To put it another way, if you need 1 acre of farm to make enough for you to eat, you'd need 10 acres to provide enough catfish food.)

    You would need much more surface space for standard agriculture.
    Agreed! And that's the good part - surface space is free; you just have to tent it. (And folded tents are a lot easier to deal with than solar panels, frames, converters, wiring, lamps etc etc,)

    Also, those panels are printed on mylar, so they're 5mm or less thick, and can be folded to save space.
    Oh, you're taking organic (non crystalline) cells. Now you are down in the 8% efficiency range. That's several times worse.

    Also, the expense of sending the panels to Mars will be far greater than the cost of the panels, so the cost doesn't really matter.
    We're talking hundreds of millions of dollars for a large array of those cells, so yes - it definitely matters! You would likely choose less efficient but cheaper panels.

    A few hundred megawatts, not a few KW, but maybe it won't be enough. We could always point two of the three microwave beams at the north pole.
    Again, if you have the technology/money to do that, build a big mirror and point it at the north pole. WAY cheaper.
    1) When fed on duckweed alone, intake rate was low, feed conversion ratio good (1:1) and relative growth rate poor (0.67% of bodyweight daily). Sixty-five percent of the duckweed consumed was assimilated and 26% converted to fish. When the fish were fed on pellets in addition to duckweed the rate of duckweed consumption decreased and growth rate of the fish doubled with feed conversion ratios between 1.2 and 1.8. Seventy percent of the mixed diet was assimilated but only 21% converted. Fish grown on the mixed diet performed similarly to fish grown on pellets but had a better feed conversion ratio.
    Quoted from Duckweed as a Primary Feedstock for Aquaculture
    so 4:1 rate.
    And if you really want to make food, also from that sight:
    Recent work with Lemna paucicostata in Nigeria (Mibagwu, and Adeniji, 1988) indicates an especially high nutritional value. Their analyses of plants from three locations in the Kainji lake area showed a crude protein ranging from 26.3-45.5% of dry weight.
    "The amino acid content compared favourably with that of blood, soyabean and cottonseed meals and considerably exceeded that of groundnut meal. The levels of the essential amino acids surpassed the FAO reference pattern, except for methionine which met 61.4% of the recommended value. The levels of minerals were high but should not pose any toxicity problems if incorporated into animal feeds. The levels of nitrogen in the plant are comparable to those in commercial fertilizers. The plant could be a good dietary supplement and nutrient source for humans, livestock and fish...." "With an average standing crop of 309 kg dry mass/ha and doubling time of 1.2 d, 129 kg DM/ha of dry duckweed are obtainable daily in the Kainji Lake area, which could ensure a daily supply of 59 kg of high-quality protein for poultry and fish feed formulation...."

    2) You also have to fill them with air (including nitrogen, which is hard to get) and oxygen, which has to be processed. Also have to process soil.
    And if you're building underground to protect against radiation, space is at a premium. And more surface area means more of a chance of micrometeorite impact.

    3) Can you show me a website that says that panels like that are that efficient?

    4) It costs hundreds of millions of dollars to send a few tons of them into space. How much would they weigh?

    5) The point is that you can expand your power supply when needed without waiting on a 6 month shipment from Earth. Very important when everything depends on your power supply.
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    Quote Originally Posted by skeptic View Post
    I am still very cynical about the idea of using solar panels for energy. I do not think those who suggest this 'solution' appreciate just how much energy will be required. To get all power direct from the sun will require literally square miles of solar panels.
    You'd need about 1000 square meters to get 100 kilowatts, which would likely be sufficient to power a base with 4 people on it. (For reference the ISS has 84 kilowatts of solar and can support 6 crewmembers.) At 300 W/kg you'd have to transport 333 kilograms which doesn't seem like it would break the bank in terms of weight. (It is well within the limits for the Mars Direct reference design for example.)

    By the time any colony is ready to be started on Mars, mini nuclear reactors will be available, and they will be able to supply almost unlimited energy.
    How much will they weigh, and how much power will they produce?
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    You cannot compare the power needs of the ISS, which has all its food, water, oxygen etc transported to it by rocket, with a Mars colony, which will have to manufacture its own raw materials, extract water, concentrate atmosphere, melt rock etc. I would not even like to begin to estimate the power needs, but it is likely to be orders of magnitude greater than the ISS on a per person basis. We are talking of a colony that has to be largely self sustaining.

    On the size of an advanced nuclear reactor. The smallest is likely to be not much bigger than a refrigerator, or maybe a small car. No larger in volume, though a lot heavier, than current Mars robot explorers. Hard to say for sure, since the development is not complete, but it looks as though they can be built quite small. There will be extra construction required, that surrounds, but is not part of the reactor. But most of that can be built from Mars sourced raw materials.
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    You cannot compare the power needs of the ISS, which has all its food, water, oxygen etc transported to it by rocket
    The ISS recycles its water and generates most of its own oxygen - and does not have ready sources of external water, oxygen and carbon dioxide as Mars does. In many ways Mars explorers will have far more resources (albeit in a less refined form) than the ISS has access to.

    On the size of an advanced nuclear reactor. The smallest is likely to be not much bigger than a refrigerator, or maybe a small car.
    Agreed. But how much will it weigh? That's the critical part.

    There will be extra construction required, that surrounds, but is not part of the reactor.
    I assume you are not referring to the primary or secondary coolant loop plumbing! Or even the turbine or heat exchanger. Those are far too critical to try to make out of local materials. However, local materials may well be able to be used for the structure to contain the entire assembly.

    Nuclear power is great, but any Mars power source will be limited by the weight we can carry from Earth.
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    You are repeating the same error.

    A Mars colony cannot be compared to the ISS. The colony is building for the future, creating an expanding and self sustaining community. It will need to extract metals from Mars dust and rock, which requires enormous amounts of energy. Just look at an Earth smelter, which has lots of advantages over a Mars equivalent. The materials extracted will need to be shaped and moulded into the things the colonists need. Getting new parts, and new materials, and food, and oxygen and water from Earth will not be possible. Energy needs will be colossal - many times the amount needed per person for anyone living on Earth.

    A travelling wave reactor seems to me to be the most likely energy source, assuming nothing better is designed in the next couple decades. It runs on uranium 238, which is ubiquitous on Earth, and probably is abundant on Mars also. (Your body is about 1 ppm U238). The reactor and its generator will have to be sent from Earth, but the water and steam handling piping etc will have to be made on Mars. This is entirely feasible if we assume 2 decades worth of advances in 3D printer technology, and a portable electric arc smelter to get the first materials needed.

    The first few colonists will not, of course, have a reactor, and will have to glean energy from lesser sources. This will make both survival and growth very difficult. They will look forward to getting the reactor.
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    Quote Originally Posted by skeptic View Post
    A Mars colony cannot be compared to the ISS. The colony is building for the future, creating an expanding and self sustaining community.
    It will eventually turn into that - but initially survival will be more important than expansion.

    It will need to extract metals from Mars dust and rock, which requires enormous amounts of energy.
    It will take a long time to get to the point where people are mining, refining, smelting, extruding and working metals on Mars. That takes a very large infrastructure which we will not have at first. At first we'll use what we bring and local materials in the form of earth (to shield tents) and bricks (to make basic shelter.) As we increase the number of people, and we get more infrastructure there and more talent, people will start to be able to do things like mining.

    Just look at an Earth smelter, which has lots of advantages over a Mars equivalent.
    Don't just look at the smelter. Look at the mines where the metal is extracted. Look at the railroads (or roads) used to move the ore. Look at the smelters, and the extruders, and the metal handling equipment. Look at the fabricating that takes place after that. Then add up all the draglines, railroads, tractors, engines, fuel, power, oxygen, controllers, cranes, roads, pipes, buildings and ovens. Now compare all that to what you can fit into (for example) a Mars Direct lander. Won't work - not for decades. Bricks will be a lot more important to early settlers than reactors.

    Want to smelt? First you need the mines. Want to mine? First you need the railroads. Want railroads? First you need the track and the rolling stock. Want the rolling stock? First you need the engines - and then you need fuel for those engines. It's not a matter of getting a reactor up there and starting to smelt.

    A travelling wave reactor seems to me to be the most likely energy source, assuming nothing better is designed in the next couple decades. It runs on uranium 238, which is ubiquitous on Earth, and probably is abundant on Mars also. (Your body is about 1 ppm U238). The reactor and its generator will have to be sent from Earth
    Will it be as reliable as the PM-3A? That was a reactor designed for just what you had in mind. It was small, light and modular, designed to be delivered in several 30,000 pound packages. (That's 14 metric tons a load.) It was intended as a very simple to operate reactor that would last for decades. It was low power (about a megawatt) but it would definitely help with oil usage in Antarctica, which is where it was delivered.

    It lasted less than ten years, when welds started failing and the reactor started leaking. It was dismantled and hauled away, and the earth beneath it dug up and transported to a waste disposal site.

    Keep in mind that's with all the factory designed piping; it just bolted together. In-situ plumbing is going to be a lot more problematic.

    So yes, a nuclear reactor is a great idea for long term power on Mars. But we have a long, long way to go before

    1) we need that much power
    2) we have a reliable source of that much power
    3) we have the technology to lift and deliver that kind of load

    The first few colonists will not, of course, have a reactor, and will have to glean energy from lesser sources. This will make both survival and growth very difficult. They will look forward to getting the reactor.
    Let's hope their experience is better than the workers at McMurdo had. Imagine being on Mars and finding out that your reactor is leaking, and your reactor building is no longer habitable.
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    If we assume the Mars colony begins in 10 to 20 years (more likely 20, in my view) there will be technology we do not yet have. An obvious gizmo will be a mini electric arc smelter. This will produce stuff from Mars dust and Mars rock. No, the colonists will not need bricks so much. If they do, they will have to carve those 'bricks' out of solid rock, since there is not likely to be any clay for baking into bricks.

    They will need diggers for creating underground habitat, though that might initially be pick and shovel. They will need to smelt metals, which assuming 20 years development and small scale production at first, should be very practical. They will not have mines, or railroads, or any major infrastructure. Picks and shovels and wheelbarrows more likely, and a mini smelter to produce metal by the kilogram, along with a range of other products, such as foamed rock insulation, possibly in brick form.

    I agree the full reactor will not be there initially. But if there is a serious attempt at a colony, which will be self sustaining and will expand with babies being born, it will not take too long before it becomes vital and urgent. Developers are working now on generation 4 nuclear reactors, which will be smaller, safer, and with less need for maintenance than earlier ones. I think there would be little doubt about the superiority of such a product over your McMurdo reactor.
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    are there ore bodies on mars like on earth? does the lack of plate tectonics have a bearing on ore body formation? if there are no ore bodies then wont mining be a waste of time? and if so then maybe mining the asteroids instead would be better and use mars as a base for that.
    Sometimes it is better not knowing than having an answer that may be wrong.
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    To Chrispen.

    I am sure there are ore bodies on Mars, but I have no firm data.
    However, I am sure that extraction of useful minerals can be done anyway. When I was a lot younger, I worked for a company (as industrial chemist) that used an electric arc furnace to melt basalt to make rock fibre insulation. One of the side products was iron, which was removed in the process, since it interfered with the fibre forming process. We sold the iron.

    Witin a couple decades, I am sure that the technology will permit a lot more than just iron to be extracted. Obviously an enriched ore would permit more metal to be extracted at a lower cost. But even without that, useful metals will be extracted from rock. Just at a much higher cost of time and energy.
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    I think the presence of usable fissionable ore is a serious problem for a home-grown nuclear industry on Mars - whilst volcanic processes have created usable uranium ore bodies here on Earth they are less concentrated than those formed hydrothermally. I expect they are essential precursors to those hydrothermally formed as well. Except for one locale in Russia all the working Uranium mines rely on hydrothermally created ores. Isn't there a place in Africa where concentrations rose high enough that way for fission events to occur? Natural enrichment within ore bodies is crucial as well - because most primordial isotopes will have decayed long ago without it. In any case both geological processes that created U ore bodies on Earth were weaker and went on for shorter time scales on Mars. And ceased long ago. I don't know that it's impossible to find usable ore bodies on Mars but it's a mistake to presume they'll be there.

    There'll be even less chance of finding fissionable ores in asteroids of course. As far as places to set up for business in the solar system they do look more attractive to me than Mars. If 'attractive' is the right word for becoming a miner that gets to live in the mine.
    Last edited by Ken Fabos; August 29th, 2013 at 06:00 PM.
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    While that may be correct, the discovery and extraction of uranium metal has never been much of a problem on Earth, and I doubt it will be much of a problem on Mars either. The real problem has been the purification of the uranium 235 isotope. But the new micro-reactor (the travelling wave reactor) is perfectly capable of working on the mined uranium metal, which is mostly U238.
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    Skeptic, my point was that it's Earth's unique geological history that produced those ore bodies. Mars' different geological history makes those conditions that lead to those concentrated ore bodies less likely to occur or endure long enough. It's a big leap to presume finding them on Mars won't be a problem.
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    Quote Originally Posted by Ken Fabos View Post
    Skeptic, my point was that it's Earth's unique geological history that produced those ore bodies. Mars' different geological history makes those conditions that lead to those concentrated ore bodies less likely to occur or endure long enough. It's a big leap to presume finding them on Mars won't be a problem.
    Uranium is likely just dispersed through the planet instead of concentrated then. 2% of Earth's mass is Uranium. It's probably similar for Mars. Even at 100 ppm, though, they will produce large amounts during the refining process because they are processing huge amounts or regolith and rock.
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    Quote Originally Posted by skeptic View Post
    Lynx

    Realistically, you are not going to escape the need to provide heat and light. Mars is just too damn cold. Even using a heated dome to grow crops, you will need lots of energy. The dome itself would have to be multiply insulated, meaning that a lot of the sun's light will simply not penetrate, and artificial light will need to be added. In spite of that insulation, a lot of heat will escape anyway, meaning a lot of heat will need to be added on a regular basis.

    Bearing in mind the need to spend most of colonist time underground, to avoid harmful radiation, why not just dig deep caves and insulate them, and add sunlight lamps, and grow crops close to the living area?
    I disagree. Most of the tropic climate zone near the equator on Mars reach well above freezing in all seasons and would only need a means to insulate them at night and a relatively minor bump heating and thermal mass to keep them above freezing. Already addressed the solar light issue...many food plants already do well on much less than Earth's insolation levels--anything that does well in partial shade will love Mars. No need for artificial lighting needed at all for those crops. Other crops that might need more can be enhanced with application of reflective surfaces etc. And it's almost certain we'd get more by selecting plants for Mars. Such an approach would be relative low tech, easier to build, maintain and probably much more reliable than a brute force high energy, high tech approach.
    Last edited by Lynx_Fox; August 29th, 2013 at 08:15 PM.
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by Ken Fabos View Post
    Skeptic, my point was that it's Earth's unique geological history that produced those ore bodies. Mars' different geological history makes those conditions that lead to those concentrated ore bodies less likely to occur or endure long enough. It's a big leap to presume finding them on Mars won't be a problem.
    Uranium is likely just dispersed through the planet instead of concentrated then. 2% of Earth's mass is Uranium. It's probably similar for Mars. Even at 100 ppm, though, they will produce large amounts during the refining process because they are processing huge amounts or regolith and rock.
    I think no - without being concentrated it misses out on the natural enrichment process and all that's left without that is the primordial uranium, that will largely be gone due to radioactive decay. If it were straightforward to pull out parts per million from ores, we'd be doing it; we concentrate our efforts where the concentrations are for sound reasons. Processing huge amounts of regolith and rock are unlikely unless there are minerals that are worth the effort. And that effort has to be a lot harder than anything similar here on Earth.
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    I understood your point.
    However, there is ample evidence of ancient vulcanism on Mars, plus water flows. Hydrothermal deposits are probable.

    Even if I am wrong, bear in mind that we are currently extracting 0.5 parts per million of U235 from deposits on Earth. Since even your body contains 1 ppm of U238, it would seem very, very unlikely that we cannot find something on Mars with more than 1 ppm of U238. In fact, my personal prediction is that the surface of Mars will have more, not less uranium than te surface of Earth. My logic is based on the much lower gravity. On Earth, heavy atoms tend to migrate under gravity towards the core. Ths would happen to a much lesser extent on Mars.

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    Quote Originally Posted by Ken Fabos View Post
    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by Ken Fabos View Post
    Skeptic, my point was that it's Earth's unique geological history that produced those ore bodies. Mars' different geological history makes those conditions that lead to those concentrated ore bodies less likely to occur or endure long enough. It's a big leap to presume finding them on Mars won't be a problem.
    Uranium is likely just dispersed through the planet instead of concentrated then. 2% of Earth's mass is Uranium. It's probably similar for Mars. Even at 100 ppm, though, they will produce large amounts during the refining process because they are processing huge amounts or regolith and rock.
    I think no - without being concentrated it misses out on the natural enrichment process and all that's left without that is the primordial uranium, that will largely be gone due to radioactive decay. If it were straightforward to pull out parts per million from ores, we'd be doing it; we concentrate our efforts where the concentrations are for sound reasons. Processing huge amounts of regolith and rock are unlikely unless there are minerals that are worth the effort. And that effort has to be a lot harder than anything similar here on Earth.
    So uranium's Billions of years halflife will be accelerated on mars? Or will the lack of techtonic activity in the present day mean that it isn't mixed in with the planet near the surface?
    Uranium wasn't created there, just concentrated.

    We don't do that on Earth because the ground contains veins of metals and it's more efficient to get metals by mining veins. If that's not an option, or for valuable materials, it makes since to do chemical leaching or some other refining process that can get them.
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    To Lynx

    A relatively "low tech" approach will be used in the beginning, but that will require a multi billion dollar investment to deliver very basic supplies.
    Longer term will require high energy technologies to survive, by making the things the colonists need on site, from Mars resources.

    You are correct that Mars equatorial summer temperatures during the day can be almost balmy. But at night, they drop to that of the South Pole in winter. You will not escape the need to heat your hypothetical agricultural dome, and have to apply masses of heat.
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  88. #87  
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    Quote Originally Posted by skeptic View Post
    To Lynx

    A relatively "low tech" approach will be used in the beginning, but that will require a multi billion dollar investment to deliver very basic supplies.
    Longer term will require high energy technologies to survive, by making the things the colonists need on site, from Mars resources.

    You are correct that Mars equatorial summer temperatures during the day can be almost balmy. But at night, they drop to that of the South Pole in winter. You will not escape the need to heat your hypothetical agricultural dome, and have to apply masses of heat.
    Night cold isn't going to mater very much. And given the low conductivity because of the low density atmosphere low-emission coatings and other relatively simple insulation strategies will work very well to hold the day time heating. In addition, because there is very little diffuse lighting due to lack of clouds, most of the greenhouse surface can be covering in a think opaque and even better insulation materials--the only transparent parts are that required for the direct sunlight. Back some 25 years ago, when I was working with solar, there were pit greenhouses operating during Maine's short and quite cold winter days, oven sub-zero F for days, that needed hardly any heating--and they didn't have the benefits of low-e glass. The only reason we don't see more of these at the commercial level now, is because it can't complete with cheap transportation systems that can bring food from more equatorial latitudes.

    I completely agree there's going to need to be a lot of high tech to build a self sufficient colony...but the best strategies of all are likely to be a practical blend of high tech and low-tech where it makes sense--growing food with sunlight is one of those obviously places where low-tech approach is practical and likely the best strategy.
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    A minus 80 Celsius night will require no heating????

    Get real.
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    Why do you think it matter how cold the night is? The heat needs a way to escape, no matter how cold it is outside.

    The structure in contact with the ground can easily be insulated with current tech. The only challenge is insulating the small transparent section through a combination of using materials with good thermal properties to reduce heat transfer to the surface interface with the Mars atmosphere and low Ir emmision materials since it's about the ONLY way heat can escape to the atmosphere (almost no conductive loss). It might be a mechanical means such as moveable covers or blown insulation. Better yet and simpler, probably go with some form of silicon aerogels, which are transparent to visible radiation and reduce conductive transmission to less than 0.01 W/mK. During the day its taking in a more than a KW per square meter, at night only loosing a few hundred watts. Very low tech thermal mass inside the structure maintains a level temperature. It's not nearly as big a problem as you seem to think it is.
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    Can they construct aerogels on Mars? It's light weight, but they would need so much of it to insulate the domes that it would be difficult to carry enough to insulate everything.
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    To Lynx

    You are well aware of the laws of thermodynamics. Loss of heat increases according to the thermal gradient. When the interior of a Mars agricultural dome is 20 C in order to grow crops, and the outside temperature drops at night to minus 80, then there will be massive heat loss. Even using good insulators will only slow the loss, not stop that. So the interior of the dome has to be heated, or else all your crops will turn to ice blocks at night. All the mirrors in the world are useless at night.

    It is worth remembering that, on average, the surface of Mars is substantially colder than Antarctica. We cannot grow crops in Antarctica without adding heat. It is worse on Mars.

    The use of insulation and reflecting mirrors will reduce the need for heat, but not remove it. If you have a dome big enough to grow crops for a reasonable sized colony, you are going to need enormous amounts of heat. If you try to get that heat from solar cells, or mirrors, you are going to need enough to cover a massive area. And they will cease to do anything at night.

    Add in the need to smelt metals, and other activities to permit long term colony survival, and you need something more than solar cells and mirrors. I am suggesting a micro nuclear reactor. These are under development as I write. They are safe, small, and generate enough power for a small town.
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    Billvon - U 238 has a very long half life - more than 4 billion years, that is true. U 235 is around 700 million. But that doesn't alter the fact that, without the enrichment that comes from being concentrated by geological processes it's been decay all the way. The uranium ore bodies we mine are as much a product of that enrichment as of the concentration of primordial isotopes. It's a big assumption that Mars geology produced similar ore bodies and that finding usable Uranium ore is just a matter of looking.
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    Could Mars make glass? That's the biggest weight concern for solar panels, not counting the power storage. If that could be made on Mars, we could just ship the PV material and wires and let them make some to expand their power. I'm sure you could print them with metalic ink for the wires and PV ink for the solar cells.
    That would work better on the moon, and the dust storms on Mars would scratch them, but in orbit that wouldn't matter. Also, it would be good for asteroid mines for smelting ores.

    The traveling wave nuclear reactor seems the best idea so far, as it would be more reliable than solar. On Mars (because solar is too problematic and they will be processing a lot of material anyway), it's about the only viable power source that's been proposed here. The main problem would be finding uranium, thorium (a material that's 100 times more available on Earth), or some other material to fuel it when it starts to die down after a decade or two. Sufficient mining and processing facilities should fix that, though. Also, you would want to be able to make more of them eventually for expansion.
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    Quote Originally Posted by skeptic View Post
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    You are well aware of the laws of thermodynamics.
    Indeed I am and thankyou.

    Loss of heat increases according to the thermal gradient.
    But ask yourself where the effect mostly is. With the ground. Say the ground is an average of -30C, so a difference of 50C between the greenhouse and the ground. Even using good roof insulation standards of R-50 that can be built with relatively low tech Home Depot insulations we're talking about a loss of only 1 W per square meter.

    Now the quarter of so of the surface areas that make up the windows. Unlike your Antarctic example where a window will loose about 50% of it's heat to conduction and convection into the atmosphere, Mar's atmosphere is so thin its very low %, only a couple % at most. (it's easier to keep things warm in space than on Earth because of this). This is also why outside temp matters much less on Mars than it does on Earth. What's left is radiation loss. Just looking at black body numbers and Stephen Boltzmann law, that's about 400 W per square meter at 20C...and it's 25/7 (for that bit longer day!...haha). But if we add already available low-E coating to that uninsulated glass you can get as low as 0.1 emmisivity...thus 40W per square meter. If you add the silica aerogels, most of which still allow good visible transmission (even better if from Mars) you can bring that down to 10W per square meter. Those sorts of energy losses aren't at all that difficult to keep up with versus the nearly cloudless and reliable direct Solar gains of several hundred watts per square meter for half the day.

    Neither heating the domes or the living structures are going to be serious drain on energy for the colony even if built with currently available technology. Not sure how much will be needed to keep good air and water quality..that might be more energy intensive in a closed system.

    The manufacturing side is where you're going to need most of that energy.

    --
    I wouldn't worry too much about scratched glass on Mars.... the atmosphere is so thin neither wind abrasion or dynamic load are big concerns.
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    Consider that by the time we get a Mars colony going. We will probably be mining asteroids and I'm sure some of that mined material could be very useful to the colonist and much easier to get than importing it from Earth. Much of that space mining technology could also be very useful to the martian colonist. Also, producing energy will create heat that can be used in areas where heat loss is of concern. On Earth we are very wasteful of just about everything. On Mars everything that can be recycled will be.
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    Again, I understand your reasoning, which, as always, is very sound. My only quibble is your appreciation of how cold it is on Mars. Average temperature is minus 55 C, and even on the equator, at night, it drops a lot lower than that. The lack of atmosphere reduces heat loss from the dome, but it also drastically increases heat loss at night from the planet. Your insulation would have to cope with a temperature gradient of at least 100 C.

    I do agree, though, that heating a dome would not be the major use of energy. Manufacturing and extraction of raw materials would take far more energy.
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    Quote Originally Posted by skeptic View Post
    The lack of atmosphere reduces heat loss from the dome, but it also drastically increases heat loss at night from the planet.
    Agreed. Much lower conducted heat loss, much higher radiative heat loss. However, radiative heat loss is much, much easier to deal with through the use of glass (passes short wavelengths, blocks long wavelengths) and anti-emissive coatings.

    Your insulation would have to cope with a temperature gradient of at least 100 C.
    Currently spacecraft deal with far higher gradients than that. The ISS, for example, is in darkness about 40% of the time during its orbit - but even in darkness, with temperatures far below -100C, they have to radiate their excess heat via big radiators.

    I do agree, though, that heating a dome would not be the major use of energy. Manufacturing and extraction of raw materials would take far more energy.
    Agreed there.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by skeptic View Post
    Bearing in mind the need to spend most of colonist time undergeround, to avoid harmful radiation, why not just dig deep caves and insulate them, and add sunlight lamps, and grow crops close to the living area?
    Because then you need 20x the area of solar panels to drive the sunlight lamps. You have to ship these from Earth, and they are expensive and heavy. Any long term plan for colonization cannot rely on underground farms with artificial light.
    Let me google that for you
    It's a Let Me Google That For You link by the way, I don't like linking directly to Google. These ultrathin iron oxide solar cells are cheap... no idea about the energy yield, though. How much more would you need compared to heavy solar panels?
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    These ultrathin iron oxide solar cells are cheap... no idea about the energy yield, though. How much more would you need compared to heavy solar panels?
    Around 2%:

    Translucent Thin Film Fe2O3 Photoanodes for Efficient Water Splitting by Sunlight:

    So you'd need 200x the area. 200 meters of solar panels for every meter of illuminated area. At some point a window is just going to be plain easier.
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    Quote Originally Posted by Ken Fabos View Post
    Sorry, 'composting' to mean breaking down by some organic method to retain the precious biological materials. Minced up into vats to become liquid nutrients more likely than a gardener's compost heap. I do think those materials - and the oxygen - are going to be too valuable to 'burn'. Most of the recovery of nutrients would have to be from the flue gases rather than ash - which seems overly energy and equipment intensive.


    But - would there be enough sunlight on Mars under a dome for efficient plant growth? Efficient agriculture and most productive crops requires full sun equivalent lighting. Also Mars doesn't have the atmosphere or magnetosphere to protect from cosmic radiation. I would expect underground and under lights would be the starting point and those are even more energy and equipment intensive. Nuclear power required - and Mars is unlikely to have accessible nuclear fuels anywhere near the surface; Earth's ores are a result of (relatively) recent concentration (and natural enrichment that results) by hydro-geothermal processes.
    Actually, the outlook is not so gloomy for martian agriculture. The hydroponic solutions you buy at the local nursery are solutions of combined dry salts and water. One metric ton of the dry salts would go a long way to maintaining production through several crop cycles. Mars has a serious overabundance of all macro-nutrients in it's soil. Way beyond what would be healthy for food plants. The soil will need to be processed and enriched before it can be used. There are also serious toxins such as chlorates and even hydrogen peroxide. I recommend going with the hydroponics while developing enclosed growth chambers based on 'standard' soil methods of growing.
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