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#21
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#22
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In article ,
"Gene P." wrote: I'd consider being isolated from your power supply 50% of the time (for two weeks at a time) to be a greater problem in need of a solution than the modest requirements for orbital station-keeping. I've got 2 different answers to this non-issue: 1. The Lunar Power Grid + electric furnace. Who cares if the electricity comes from solar panels on the other side of the moon or from a great big nuclear pile a couple of miles away... Running power lines all the way around the Moon is itself a daunting engineering challenge (though admittedly, one probably on the same order as a mass launcher and large-scale orbital manufactury). A reasonable solution, but not such a trivial one as to make lunar night a non-issue. A nuclear power plant is also a reasonable solution, but again, it doesn't offer the same flexibility or convenience as continuous sunlight. 2. Space furnace mirrors can point down at the lunar surface just as easy as at an orbital processing facility... Can they? From where? There are no selenosynchronous orbits. ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#23
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"Gene P." wrote in message ... 2. Space furnace mirrors can point down at the lunar surface just as easy as at an orbital processing facility... Wrong. Think about it. |
#24
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Then why don't we use such things on Earth? Nuclear power is WAY
cheaper in Mexico (or even Nevada compared to New York)! The fact is, transmitting power via cables over long distances is expensive. The grid uses nearby sources, not far away ones. Losses on long distance power cables become very large very fast. -David |
#25
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David Summers wrote:
[...] The fact is, transmitting power via cables over long distances is expensive. The grid uses nearby sources, not far away ones. Losses on long distance power cables become very large very fast. Well, depends on the long distance, I suppose. There's a intertie running down eastern Oregon; probably from Bonneville on the Columbia river, and probably to somewhere around Red Bluffs or Sacramento, so in excess of 300 miles doesn't seem strange. Also, 250 miles from Hoover Dam to LA. Losses would go down with superconductor cabling, which is still expensive, and the support equipment may still be prohibitively heavy. But it looks like it might be practical and available within about the same time as return to the moon. /dps -- Using Opera's revolutionary e-mail client: http://www.opera.com/m2/ |
#26
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#27
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"Gene P." wrote in message
... I've got 2 different answers to this non-issue: NASA didn't consider this a non-issue when they made the only detailed studies of space industrialization using ET resources they ever did in their history. In case you thought I was arguing from my imagination, or from what happens to strike me as reasonable, I'm arguing from the NASA Summer Studies on space settlement. 1. The Lunar Power Grid + electric furnace. Who cares if the electricity comes from solar panels on the other side of the moon or from a great big nuclear pile a couple of miles away... A power grid spanning the entire globe of the moon would be a pretty formidable industrial accomplishment. I can't see it happening in any near-term future. It would be a shame if we went to all the expense of developing nuclear power on the moon just because we couldn't overcome our planetary chauvinism long enough to develop solar power outside the shadows of planets. Nukes are fairly high-tech, large mylar mirrors are pretty low-tech. I know which is going to have the bigger power bill. With the space mirror, the heat generated is used directly without any conversions and consequent efficiency losses. 2. Space furnace mirrors can point down at the lunar surface just as easy as at an orbital processing facility... No, actually, that's where you're wrong. The optical physics of it are such that at several miles distance one would be forced to use mirror many times bigger than otherwise (and also be forced to illuminate a much wider area that what's desired). In discussing a High Frontier type solar furnace, we're discussing mirrors perhaps one or two times the area of a football field. To do what you propose would require mirrors the size of states or small nations. -- Regards, Mike Combs ---------------------------------------------------------------------- Member of the National Non-sequitur Society. We may not make much sense, but we do like pizza. |
#28
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"Joe Strout" wrote in message
... Running power lines all the way around the Moon is itself a daunting engineering challenge (though admittedly, one probably on the same order as a mass launcher and large-scale orbital manufactury). I'm not even sure it would compare favorably with those items. I'm a little bit vague on the mass budget for the orbital manufacturing facility O'Neill proposed, but as for the mass launcher, I remember him commenting that the components for the mass-driver itself would fit into a single Space Shuttle cargo bay, although the components for the power supply would be several times that. 2. Space furnace mirrors can point down at the lunar surface just as easy as at an orbital processing facility... Can they? From where? There are no selenosynchronous orbits. Yet another complication. And the L-1 and L-2 points are so far away that I think we'd be discussing mirrors bigger than continents. -- Regards, Mike Combs ---------------------------------------------------------------------- Member of the National Non-sequitur Society. We may not make much sense, but we do like pizza. |
#29
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"Fred J. McCall" wrote in message
... wrote: :I believe the lighter the molecule in the exhaust, the more efficient :the engine? If so, it might be better to make pellets of silicon (MW= :14) as we process the asteroid, charge them, and accelerate them using :an electrostatic engine. Oxygen has a molecular weight of 16, would be :rather corrosive in a high-temp exhaust, and is more useful than :silicon for other purposes. But do you really want to be spraying what are essentially high speed bullets around where they can eventually hit other spacecraft? Better something that isn't solid for your 'exhaust'. Yes, but space is already criss-crossed with high-speed micrometeoroids. So the only sensible question that needs answering is are we making a significant contribution to an already-existing problem. At many levels of scale, the answer is probably "no". That said, I remember that in the "High Frontier" plan, it was proposed that mass-drivers start out using pelletized Space Shuttle ET's for their reaction mass, but at a fairly early point switch over to locally-produced oxygen, which would vaporize on release. So the impression that I get is that it's not an issue to be disregarded, but it's not a big issue. -- Regards, Mike Combs ---------------------------------------------------------------------- Member of the National Non-sequitur Society. We may not make much sense, but we do like pizza. |
#30
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"Paul F. Dietz" wrote in message
news Mike Combs wrote: A power grid spanning the entire globe of the moon would be a pretty formidable industrial accomplishment. I can't see it happening in any near-term future. I suspect a power grid on the moon is considerably more difficult than one on earth, even ignoring the difference in labor cost. A high voltage conductor in dense air is insulated by that air, but in vacuum you'll be constantly generating high energy ions and electrons in the surrounding plasma, and possibly causing runaway discharge due to their collision with surfaces and secondary ion production. That's assuming that you'd run the cables suspended above the surface somehow... If you were serious, you'd probably direct bury them - AIUI, moon dust is a great insulator. Cameron:-) |
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