Quote from: JohnFornaro on 09/01/2012 02:14 pmShould this get a new thread? Mars-One hasn't given any credible public presentation that they have considered a garden just yet.Yeah, probably should. I dont want to start it because I might not have much more to add.The discussion above is what I meant and has produced two approaches for putting bounds on the energy requirements:* Energy to grow an acre of corn using sunlight (we can do at least this well)* Fundamental efficiency of photosynthesis - possibly improvable with selective wavelengths (we can do at most this well)(a wacky alternative could be if we could power life other than by photosynthesis, e.g. if it turned out more efficient to create a sugar or alcohol through non-biological means and fed this to some bacteria.. I have no idea if any such mechanism exists so Im not pushing it)
Should this get a new thread? Mars-One hasn't given any credible public presentation that they have considered a garden just yet.
The Mars One thread drifted into greenhouses and growing food on Mars. This thread is to continue that discussion.Some are concerned that sun light might not be strong enough on Mars to grow Earth food plants. Solar intensity at the top of Mars atmosphere ranges from 715 down to 492 W/m^2. That is about 1/2 to 1/3 of that of Earth. The wide variation is due to the eccentricity of Mars' orbit. The question is, "Can food plants be grown with only 1/3 to 1/2 the natural sunlight of Earth?" The answer is yes, because food plants grow on Earth in the band of latitudes between Munich and Siberia which only receives 1/2 to 1/3 the full solar intensity at Earth's equator, because of the high latitude. This is true even if the Mars atmosphere attenuates the solar radiation to the same extent that the Earth's atmosphere does, which is not proven.
To broaden this topic a bit though, there are other crops valuable to a new colony that are not edible. It's really to bad that duct tape doesn't grow on bushes, but rope is made from hemp, and clothing, blankets, draperies, rugs etc. from cotton. Bonsai (trees) might be nice, too. If we colonize Mars, we must live off the land.
Chemically converting carbon, hydrogen, oxygen, and nitrogen into fibers and even macronutrients using just air and water and electricity makes a lot of sense in my opinion, if it can be done effectively enough. And would be awesome on Earth as well. And should be more efficient than with plants and photosynthesis.
The discussion above is what I meant and has produced two approaches for putting bounds on the energy requirements:* Energy to grow an acre of corn using sunlight (we can do at least this well)* Fundamental efficiency of photosynthesis - possibly improvable with selective wavelengths (we can do at most this well)
(a wacky alternative could be if we could power life other than by photosynthesis, e.g. if it turned out more efficient to create a sugar or alcohol through non-biological means and fed this to some bacteria.. I have no idea if any such mechanism exists so Im not pushing it)
BTW, nobody commented on my suggestion of producing algae yet. I still believe it would solve most of the problems without the need of artificial lighting and big pressurized structures.
There are probably some delicious recipes to be cooked up from algae, I just have never tried them and more, I don't know of any. Algae sounds distasteful but if we have food animals or pets on Mars, then maybe they would eat algae based food.
Perhaps a use for algae would be as a fertilizer to condition the soil by feeding the micro orginsms needed in the soil by the plants. Of course we could most likely produce most of the fertilizer, but the needed trace elements for plant growth may require decay of prior plant (algae) growth material.
Question. If we use long, narrow greenhouses, what is the most economical way to keep them warm at night? A removable thermal blanket?
Question. Do we know how much atmospheric attenuation of sunlight results from the Mars atmosphere?
Question. If plant life existed on Mars eons ago, will the soil already be conditioned for the reintroduction of plant life?
1) 100 watthour = 85.984 522 786 Calorie [nutritional]So 100 wattday would be a 2064 Calorie a day diet, if you could eat the watts.You could actually look at it another way, by comparing field crops on earth to Calories produced. I don't want to do the work to get it right, but one acre of corn receives about 4000 kwh (~4000 m^2 at 1 kw/m^2)sunlight per hour of sun shine. 2) Discounting the energy needed to produce fertilizer, assuming 6 hour (very short) sunshine days and an 8 week (very short) growing season. Multiply that out and get 4000 kWhr * 6 hr/day * 7 days/week * 8 weeks/growing season = 1.3 GWhr to produce 150 bushels of corn. 3) Hope you like feed corn. I'd rather eat potatoes myself.
The discussion above is what I meant and has produced two approaches for putting bounds on the energy requirements...
The question is, "Can food plants be grown with only 1/3 to 1/2 the natural sunlight of Earth?" The answer is yes, because food plants grow on Earth in the band of latitudes between Munich and Siberia which only receives 1/2 to 1/3 the full solar intensity at Earth's equator, because of the high latitude.
...rope is made from hemp...
I'm curious about the energy/maintainability/space tradeoffs of growing plants for materials vs, say, producing plastic from methane
1) Although I don't know that Mars One intends a permanent long term settlement, it seems highly likely given the one way trips. 2) If you are planning the second center of human life as insurance aginst catastrophe here on Earth, then the Mars colony must be independently self sustaining without any support from Earth. 3) That means, without information or even communications, let alone any tech materials delivery. A telescope with which to view Earth would be good, but what you could see would be all the information you could count on. 4) Given the above, it is not prudent to depend on technology for which you cannot make the replacement parts or program the computers yourself on Mars. Starting with the use of advanced technology is one thing, and necessary, but an objective should be 5) to become self sufficient as soon as possible. To me, that means making our own green houses from locally made materials and growing our own food, finding our own fuel and developing away from dependence on the biannual transport from Earth. 6) Of course we would have a huge digital library and endless debate as to the need to transfer the library into paper books, but that's farther into the future. We'd also have the problem of the other colonies that are not so foreward thinking who relied on Earth with perhaps an easier lifestyle as a result.
The comparison of a methane production plant, and its associated methane conversion plant, also associated with its plastic to chair manufacturing plant, supported by its need for PV electricity or fission based electricity, would have to be compared with the incremental costs of adding forestry acreage and passive solar reflection to the biosphere, and the costs of launching a bag of carpenter's tools, including a skill saw and drill. So there's that.
One acre = 43,560 sq ft, = 4046.856 sq m. Atmospheric pressure = 101,235.01 N/sq m = 2116.22 lbs/sq ft.The total lifting force of the enclosed atmosphere = 410,047,767 N, or 92,182,405 Lbs.Circumference of the dome = 225.509 m, or 739.8588 ft.Dividing total lifting force by the circumference gives 1,818,321.28 N/m, or 124,594.59 lb/ft.Edit: We've been through this before on another thread. The dome could be held down if you put a lot of water depth on top of it. Then gravity would work to restrain the forces. But remember, the force is the same as it would be on earth, but the weight of water is not. Or you could make a heavy dome out of Mars iron, that would give the strength needed, and smaller windows would not need to withstand so much total force. I think we should consider finding a deep cave and sealing it against air leaks to live in, initially. I don't know what to do for the greenhouses, except to make them small.
So forces become huge. To make a comparison that can be intuitively understood: If you make a dome of cast iron with a wall strength of 1,5m or more than 4 feet, it would still be lifted off its foundation by airpressure on earth sea level.
The highest pressure on mars would be inside crater Hellas Planitia with ~ 1200 N/m².
Thanks for the site suggestion. But... Why are you talking force per area? Pressure would be in kg/m^2. That confuses me.