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Mars is kind of short of nitrogen
John Savard wrote:
but, as Robert Zubrin notes, it does seem to be the best place to set up a colony. However, are there any other alternatives that might be even more attractive? One of the objections Dr. Zubrin gives to O'Neill colonies is that a mirror area comparable to the crop area is required for agriculture. As it would seem to me that aluminized Mylar is easier to construct than the *land area of the colony itself*, that seems to be an odd objection. It appears to be bar far better to use solar batteries and artifical lightning combined with hydroponics. [snip] Since the gas giants have very deep gravity wells, comets and Pluto seem to be the other potential non-terrestrial sources of nitrogen in the Solar System. Remember Titan. John Savard http://home.ecn.ab.ca/~jsavard/index.html -- Sander +++ Out of cheese error +++ |
#2
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Mars is kind of short of nitrogen
"John Savard" wrote in message
... One of the objections Dr. Zubrin gives to O'Neill colonies is that a mirror area comparable to the crop area is required for agriculture. As it would seem to me that aluminized Mylar is easier to construct than the *land area of the colony itself*, that seems to be an odd objection. Odd indeed, especially since later in the same book he recommends orbital mirrors for speeding up the terraforming process on Mars. There seems to be a general assumption that Mars colonies will obviously be cheaper than orbital ones because where the latter are concerned you have to build the very land underneath your feet for crying out loud. But I question this assumption. In both cases, one must build an enormous pressure vessel. The thin atmosphere of Mars is not going to mitigate the expense of that by more than a percent or two. Unlike in a Mars dome, in O'Neill habitats the "ground" rests on the inside of the pressure shell, but any structure engineered to stand up to the air pressure can support a load of 5 or 6 feet of soil without a lot more engineering. So aside from "the ground under your feet", what else does Mars provide that must be provided artificially in an orbital habitat? The only remaining answers are gravity (the wrong amount as it happens) and a day night cycle. Once you start that orbital habitat spinning, it's going to keep spinning with practically zero ongoing expense. And I don't see what should be so difficult or expensive about making a mirror tilt. And I don't think Zubrin can even touch all of the arguments O'Neill made regarding the advantages of orbital locations over planetary ones. But the mirror area could be smaller if the colony was closer to the Sun. Very true, but given the greater presence of volatiles in the outer system, and the simplicity and modest material requirements of space mirrors, I more expect the opposite. Venus' atmosphere has about the same percentage of nitrogen in it as Mars', but it is many times denser. A well-shielded O'Neill colony - I have a design for one, shaped like a wine bottle, with a further shielding slab out past the mirrors putting light down the neck of the bottle, where the shielding doesn't rotate - in orbit about Venus might have access to a good source of biomass feedstock. (Metal and rock would be sent from the Moon.) I'd have a hard time seeing it being economically competitive to lift any kind of volatiles from Venus vs. other locations we know about. Since the gas giants have very deep gravity wells, comets and Pluto seem to be the other potential non-terrestrial sources of nitrogen in the Solar System. That's where the smart money is. -- Regards, Mike Combs ---------------------------------------------------------------------- We should ask, critically and with appeal to the numbers, whether the best site for a growing advancing industrial society is Earth, the Moon, Mars, some other planet, or somewhere else entirely. Surprisingly, the answer will be inescapable - the best site is "somewhere else entirely." Gerard O'Neill - "The High Frontier" |
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Mars is kind of short of nitrogen
"Sander Vesik" wrote in message
... It appears to be bar far better to use solar batteries and artifical lightning combined with hydroponics. I could believe this if I could believe that on a square-mile to square-mile comparison, solar panels and electric lights were comparable in price to aluminized Mylar and glass. Remember Titan. A good point. If it turns out that asteroids just can't provide the amounts of nitrogen needed, export from Titan might actually help meet the demand. -- Regards, Mike Combs ---------------------------------------------------------------------- We should ask, critically and with appeal to the numbers, whether the best site for a growing advancing industrial society is Earth, the Moon, Mars, some other planet, or somewhere else entirely. Surprisingly, the answer will be inescapable - the best site is "somewhere else entirely." Gerard O'Neill - "The High Frontier" |
#4
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Mars is kind of short of nitrogen
"Sander Vesik" wrote in message ...
John Savard wrote: One of the objections Dr. Zubrin gives to O'Neill colonies is that a mirror area comparable to the crop area is required for agriculture. As it would seem to me that aluminized Mylar is easier to construct than the *land area of the colony itself*, that seems to be an odd objection. It appears to be bar far better to use solar batteries and artifical lightning combined with hydroponics. "Lighting." The problem is that with the efficiency of these, which is limited by the laws of physics, you'll always lose at least around 80% of the original energy by converting light to electricity and back. Since the gas giants have very deep gravity wells, comets and Pluto seem to be the other potential non-terrestrial sources of nitrogen in the Solar System. Remember Titan. I think many regions of the outer Solar System will become sources of volatiles and light elements for the inner planetary orbits. And heavy elements will become the prime trading goods for the outer ones. Once humanity splits into societies inhabiting many different worlds then many will have what others need and vice versa. It's gonna be interesting... -- __ “A good leader knows when it’s best to ignore the __ ('__` screams for help and focus on the bigger picture.” '__`) //6(6; ©OOL mmiv :^)^\\ `\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/' |
#5
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Mars is kind of short of nitrogen
In article ,
lid (John Savard) wrote: but, as Robert Zubrin notes, it does seem to be the best place to set up a colony. All other factors (such as distance and travel time) being equal, certainly so. But those other factors are most decidedly NOT equal. It may still be a great place to set up a colony one day, but definitely not the best place to set up our *first* colony. ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#6
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Mars is kind of short of nitrogen
In article ,
"Ool" wrote: It appears to be bar far better to use solar batteries and artifical lightning combined with hydroponics. "Lighting." The problem is that with the efficiency of these, which is limited by the laws of physics, you'll always lose at least around 80% of the original energy by converting light to electricity and back. First: so what? Gather more energy. One of the primary points of colonizing space is that energy is cheap and abundant. Second: it doesn't even mean you need more light-gathering area (even assuming solar power), because light in orbit is available 24/7 and at much higher intensities than here on Earth. Quick calculation: if we assume 20% efficiency for light-electricity, and 55% efficiency for electricity-light (which is the current best rate, in sulfer discharge lamps), the product is 11% efficiency. Multiply by 7, for amount of sunlight available in GEO vs. the ground, and you have 77% as much light available in this way as compared to using the light directly. But this does not take into account that the artificial light generated might be more efficiently used for photosynthesis. Take that into account, and I bet you could grow MORE crops per square meter of solar panel than you could grow per square meter of dirt on Earth. ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#8
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Mars is kind of short of nitrogen
John Savard wrote: but, as Robert Zubrin notes, it does seem to be the best place to set up a colony. However, are there any other alternatives that might be even more attractive? One of the objections Dr. Zubrin gives to O'Neill colonies is that a mirror area comparable to the crop area is required for agriculture. As it would seem to me that aluminized Mylar is easier to construct than the *land area of the colony itself*, that seems to be an odd objection. You aren't the first (or the last, I imagine) to raise this point. There are many things Zubrin says I disagree with. (Although I still admire the man). But the mirror area could be smaller if the colony was closer to the Sun. Venus' atmosphere has about the same percentage of nitrogen in it as Mars', but it is many times denser. A well-shielded O'Neill colony - I have a design for one, shaped like a wine bottle, with a further shielding slab out past the mirrors putting light down the neck of the bottle, Described on this page?: http://www.hypermaths.org/quadibloc/science/spaint.htm You call your mirror system "Cassegrain"? After the parabolic mirror concentrates it into a focus it looks like a convex mirror redirects the converging rays back into parallel rays. My system is somewhat similar: http://clowder.net/hop/railroad/ChengHo.html But where you have a convex mirror redirecting converging rays to parallel, I have a smaller parabolic mirror sharing the larger parabolic's focus. Also I have a 4th mirror that reflects the parallel rays onto the sides of the cylindrical hab. It seems to me your system would also need such a mirror as parallel rays would just pass through the bottle's neck and land on disk at the bottom instead of illuminating the bottle walls. Or am I missing something? In my design the hab is built from asteroidal materials atop the north pole of the asteroid. So the asteroid provides radiation shielding over almost 2 pi steradians. The walls of the hab have a mixture of water and dirt that I hope would be adequate radition shielding from those directions. The the 4 mirrors (including the axial mirror) would shield some from the top. The top is the most vulnerable radiation leak in this colony, I believe. In future drawings I plan to make 2 habs spinning in opposite directions - one on the north and the other on the south pole. The net angular momentum is zero and so the entire mass would be more manueverable. (I stole this idea from Mike combs who has imagined two linked Bernal spheres spinning in opposite directions. His structure would also have zero net angular momentum) Also in my colony the atmosphere doesn't fill the entire cylinder - just a cylindrical shell. Less nitrogen would be needed. here the shielding doesn't rotate - in orbit about Venus might have access to a good source of biomass feedstock. (Metal and rock would be sent from the Moon.) Asteroids could also be a source of metal and rock. Since the gas giants have very deep gravity wells, comets and Pluto seem to be the other potential non-terrestrial sources of nitrogen in the Solar System. We still know very little about the composition of most asteroids. Perhaps some have ammonia or other nitrogren compounds. Especially the outer main belt and the Trojans. John Savard http://home.ecn.ab.ca/~jsavard/index.html -- Hop David http://clowder.net/hop/index.html |
#9
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Mars is kind of short of nitrogen
In article ,
Hop David wrote: Joe Strout wrote: but, as Robert Zubrin notes, it does seem to be the best place to set up a colony. All other factors (such as distance and travel time) being equal, certainly so. But those other factors are most decidedly NOT equal. It may still be a great place to set up a colony one day, but definitely not the best place to set up our *first* colony. You like the moon, right? Yep, it's true, we're very lucky to have such a large moon -- we're practically a double planet, so we can make our first offworld colonies right next door instead of halfway (or more!) across the solar system. Moreover it's a great source of raw materials for orbital colonies, too. If I believed in an intelligent Creator, I'd be thanking him for this boon of a moon which so obviously means we're meant to colonize space. To try and pass it up and dash directly for the planets is just foolishness (backed by mostly foolish arguments, as we're seeing in this thread). ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#10
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Mars is kind of short of nitrogen
Mike Combs wrote:
"Sander Vesik" wrote in message ... It appears to be bar far better to use solar batteries and artifical lightning combined with hydroponics. I could believe this if I could believe that on a square-mile to square-mile comparison, solar panels and electric lights were comparable in price to aluminized Mylar and glass. covering square kilometers with thick layers of ultraclear glass so that you both have radiation protection and not too bad light losses won't probably be cheap either. I'm quite sceptical of designs that have there be rolling fields of agriculture hapenning inside O'Neill colonies - it seems like both not overly thought out and very wasteful of space. -- Regards, Mike Combs ---------------------------------------------------------------------- We should ask, critically and with appeal to the numbers, whether the best site for a growing advancing industrial society is Earth, the Moon, Mars, some other planet, or somewhere else entirely. Surprisingly, the answer will be inescapable - the best site is "somewhere else entirely." Gerard O'Neill - "The High Frontier" -- Sander +++ Out of cheese error +++ |
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