Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Sat, 25 May 91 01:40:13 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 25 May 91 01:40:05 -0400 (EDT) Subject: SPACE Digest V13 #577 SPACE Digest Volume 13 : Issue 577 Today's Topics: Status of JPL/LMSC 55m dia. Wrap-Rib Antenna Project? Powersat R&D (was Re: SPACE Digest V13 #516) Re: SPACE STATION FREEDOM WOUNDED Re: SPACE STATION FREEDOM WOUNDED Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 13 May 91 13:57:44 GMT From: eru!hagbard!sunic!mcsun!ukc!cam-eng!dscy@bloom-beacon.mit.edu (D.S.C. Yap) Subject: Status of JPL/LMSC 55m dia. Wrap-Rib Antenna Project? About ten years ago there was a proposal put forth by JPL and LMSC to build a large space based antenna. The reflector was of a wrap-rib design (structural ribs wrapped around a central hub, then unwrapped at deployment) and roughly 55m in diameter. The thing was to go up in a space shuttle around 86-87, but, of course, the Challenger episode may have done in those plans. I need to know the status of that project. If you know anything about it, could you please email me (our newsfeed has been flakey). Thanks a lot. Cheers, Davin -- .oO tuohtiw esoht fo noitanigami eht ot gnihton evael Oo. Davin Yap, University Engineering Department, Cambridge, England --> dscy@eng.cam.ac.uk <-- ------------------------------ Date: 16 May 91 08:59:10 GMT From: snorkelwacker.mit.edu!think.com!spool.mu.edu!munnari.oz.au!mel.dit.csiro.au!latcs1!burns@bloom-beacon.mit.edu (Jonathan Burns) Subject: Powersat R&D (was Re: SPACE Digest V13 #516) In article <2829@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: > I'm sorry, but I don't see the big $$ for private industry in returning > asteroidal heavy metals, or even diamonds, to Earth. The total program > costs for fetching the materials don't seem at all competitive with local > sources of the material. { E.g. gold, diamonds cheaper to produce on Earth, and launch. } > Iron, lead, etc are so plentiful on Earth that they aren't even in > the running. > What could be profitable would be returning iron, aluminum, oxygen, > hydrogen, and the like to Earth orbit for use there. Getting rid of > the launch costs for these *bulk* materials makes sense. However, there > is presently no market for such materials in LEO, nor is there much > of a prospect of one in the next twenty to fifty years. I agree; but that's assuming we're thinking in terms of 1990 demand for materials and power, expressed monetarily. Assume 50% per capita USA consumption * 2010 world population, and some utopian financial regime permitting that population to bid for same, and it's another story. Extremes of policy are: keep hi-tech goods unaffordable to half the world, or develop world resources to the limits. At some point we have to compare fission breeders on ~1000 GW scale (counting in all transport & safety costs) with powersats. Maybe not in 20 years. But I'm very uncomfortable with the idea of living in 2010, looking ahead to 2040, and powersats still in dreamland. > The smelters, > the rolling mills, the fuel refining plants don't exist to use the > materials. The construction companies that would use the processed materials > don't exist. The projects those construction companies would build don't > exist. There is no paying demand for such projects. Again, I agree. A chicken-and-egg problem which might well keep space industrialization out of reach for another 50 years. The hope that we can break out is a slim one. It seems to rest on the prospect of an industrial revolution happening on paper, identifying the high-profit areas much more by planning than experiment. O'Neill changed things by postulating the supply and demand sides both at once. The colonies need the raw materials, moonbase needs biomass, Earth needs the power. Too optimistic, fell over. But a real scenario has to work this way. > People on this list even want to kill Fred, the first stepping stone > to building an infrastucture that would generate demand for bulk > materials in orbit. We'd all look silly if we had only proposals for generating demand which squeezed out proposals for generating supply, and vice-versa. The Nick Szabo line is that there are relatively cheap measures with high leverage on verifying supply. That is, supply of carbon, silica, alumina, ore-grade metals: bulk basics. On this, he persuades me. He also thinks that processing can be demonstrated similarly using unmanned facilities, taking teleoperation into account. And that a platform should not be so expensive as to squeeze out these demonstrations, over the next 10-20 years. I think the argument whether a manned platform or teleoperation would better enable the demonstrations still has a way to run. I want to see a lot more paper work on proposals for processing, before I'm sure what kind of platform to put up. > Mining the asteroids for materials to_be_used_in_space makes sense over > the long term. There is no hurry in the next twenty to fifty years, > however. Speaking for space, what we have to sell is sunlight and volume*vacuum. If we don't have customers for those, we don't have customers. I want proposals for: * Very large mirrors * Large-scale application of carbon-vapour-deposition to custom diamond manufacture * Research on non-imaging concentrators, including first-stage smelting, and monatomic hydrogen production * Very large scale vacuum-tube technology, including element separation * Low-gravity magnetic bearing systems in vacuum * High-intensity-light-pumped lasers * Tunable free-electron lasers * Very large radiators And I want them all to look good enough on paper, that they will justify either a manned platform or a teleop kit to support the large-scale versions soon. I want these things, because in twenty years, I want to _cost_ a terawatt beamed to Earth. Badly. I can't prove that powersats will be The demand that kicks space industry off. That's world politics. However, if the powersats are not at least costable by 2010, the alternatives in 2030 are: (a) a terawatt of burning coal (b) a terawatt of fission (c) world-wide industrial deprivation for lack of power. How many times have we told friends, "If you're serious about sustainable growth, you must become a serious supporter of space industry." It is fairly scary to hear the informed space community saying, "No hurry for twenty to fifty years." I don't want to misrepresent you on that, Gary. I know you were replying to space+%ANDREW.CMU.EDU@msu.edu, who said: >If NASA, a gov agency, could get guys on the moon, in ten years, with >National Prestige/Fear the motivation, think what PI could do, with >Big $$ as the motivation. Especially with the experince we have now. to the effect that the $$ could not be promised. I'm in the awkward position of having to mark up powersat value against questionable costs such as greenhouse, large isotope inventories, and/or agrarian poverty. But I am certain that powersat demand can be anticipated in the 20-50 year timeframe, as the _first_ benefit of major space industrialization. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Jonathan Burns | They finally discovered that the ONE thing burns@latcs1.lat.oz.au| they just could not _STAND_ was a smartass Computer Science Dept | commenting decompiler ... La Trobe University | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ------------------------------ Date: 16 May 91 15:49:50 GMT From: usc!rpi!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: SPACE STATION FREEDOM WOUNDED In article <1991May16.090453.2293@sequent.com> szabo@sequent.com writes: >>... They're dreaming if they think it will have >>more than a momentary effect on their own financial problems. > >Even a _momentary_ effect is enough to pay for [various things] >That's right, _all_ of that, spread over several years, costs just >one year of peak Fred funding (c. $10 billion by GAO estimates). Ah, I see. One year of the mythical peak Fred funding would pay for a bunch of worthwhile projects. Has it not occurred to you that no space projects will ever see that funding if Fred dies? (Probably not if it lives, for that matter.) You're fantasizing here, Nick; my comment still stands. -- And the bean-counter replied, | Henry Spencer @ U of Toronto Zoology "beans are more important". | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 17 May 91 03:11:09 GMT From: ogicse!sequent!muncher.sequent.com!szabo@decwrl.dec.com Subject: Re: SPACE STATION FREEDOM WOUNDED In article <1991May16.135819.5065@ux1.cso.uiuc.edu> mcdonald@aries.scs.uiuc.edu (Doug McDonald) writes: >>What do you expect? In all government-dominated fields everything >>seems to degenerate into a zero-sum game. > >That is MOST EMPHATICALLY not true: the pie is getting bigger every day. No wonder my paycheck is getting smaller every day... :-( -- Nick Szabo szabo@sequent.com "If you understand something the first time you see it, you probably knew it already. The more bewildered you are, the more successful the mission was." -- Ed Stone, Voyager space explorer ------------------------------ End of SPACE Digest V13 #577 *******************