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 ; Wed, 10 Apr 91 01:40:16 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 10 Apr 91 01:40:10 -0400 (EDT) Subject: SPACE Digest V13 #384 SPACE Digest Volume 13 : Issue 384 Today's Topics: Re: Laser launchers Re: Fred on the Moon Farmers Storm NASA Tracking Station in Australia Re: Laser launchers Re: Space technology Re: Space technology Qeustion: OSC's Engineering Dpt. Address Re: spacesuits (Was: Re: HST in-orbit Maintenance) Re: Launch Technology: back-up crews 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: 9 Apr 91 18:38:17 GMT From: usc!rpi!news-server.csri.toronto.edu!utzoo!henry@apple.com (Henry Spencer) Subject: Re: Laser launchers In article <2706@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: >>If you're willing to settle for 20kg per shot, the laser is still big but >>is the sort of thing that could reasonably be built as a custom job today. >>Funding is a much bigger problem than technology. > >Even to place a 20 kg payload in orbit would be quite a trick. The only >laser technology capable of sufficient power is the gas dynamic laser. Nonsense. Outfits like Avco will happily build you a CO2 laser of the required size, if you're willing to pay for it. (Well, it will be a bank of lasers rather than a single tube, but the net effect will be the same.) There is some small risk involved, since it will be an unprecedentedly large laser, but for a 20kg system it's felt to be a reasonably understood scaling of existing lasers. >... It would take at least 100 times >as much fuel to power such a laser as would be required by a chemical >rocket to launch the same payload. The economics of the matter have been studied; they look feasible. CO2 lasers run on electrical power, not chemical fuels. The amount of power needed for a 20kg system is hefty, but not to the point of needing to build your own power plant. >And that's if laser launching is >even possible. The adaptive optics required to deal with the problem >of atmospheric blooming while handling the enormous power of the beam >are beyond the current state of the art... This is not what the LLNL people working on laser launchers say. SDI, for all its flaws, has made a lot of progress in things like high-energy optics. And the beam power for 20kg is not that staggering, especially since it can be at relatively long wavelengths where the optical problems are easier. >... The major flaw of laser >launchers is that they have to deliver all of the power necessary to orbit >a payload through the thick lower atmosphere for the entire boost phase. This *is* a nuisance. Putting the system on a mountaintop would help. >This incurs a terrible efficiency penalty as well as being incredibly >loud. The loud part I'll agree with, especially when the payload is still at low altitude. It's manageable. A rocket is kind of noisy too. >... Like the chimera of controlled nuclear fusion, they are >unlikely to deliver any useful results even after hundreds of billions >of dollars and decades of effort are expended on them. My my, aren't we negative today? :-) These systems are somewhat speculative, but we'd know a whole lot more about how practical they are if we spent, say, a few hundred million on building and testing prototypes. The 20kg laser launcher, win or lose, would not cost billions. >small clever rockets like Pegasus, and eventually, direct to orbit >aerospace planes are much more likely to be sucessful at delivering >payloads to orbit economically and in a realistic timeframe. Ah, direct-to-orbit aerospace planes. As Gary Hudson put it, roughly, "this thing is a cross between the Concorde and the Shuttle and you think it's going to be cheap and on schedule?". -- "The stories one hears about putting up | Henry Spencer @ U of Toronto Zoology SunOS 4.1.1 are all true." -D. Harrison| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 9 Apr 91 18:51:34 GMT From: eru!hagbard!sunic!mcsun!inesc!unl!unl!jpc@bloom-beacon.mit.edu (Jose Pina Coelho) Subject: Re: Fred on the Moon In article <1991Apr9.031159.19537@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: In article <1991Apr8.221434.29272@watdragon.waterloo.edu> jdnicoll@watyew.uwaterloo.ca (James Davis Nicoll) writes: > The minimum energy orbit takes, what, about five days? Correct. But you can't have something like a Saturn V fueled, so we have a minimun of 3 days of trip plus time to get the emergency solutioning equipment ready and assembled plus(1) time to fuel the beast(2). Other inconveniences: Supplies: the energy difference between getting them into low orbit and getting them to the moon is quite big. No 0G. Basicaly the startup cost is dozens/hundreds of times that of LEO. Politics, politics, politics ... (1) - Nobody is going to start piling things on a fueled rocket. (2) - How long did it take to fuel them ? Henry ? -- Jose Pedro T. Pina Coelho | BITNET/Internet: jpc@fct.unl.pt Rua Jau N 1, 2 Dto | UUCP: ...!mcsun!unl!jpc 1300 Lisboa, PORTUGAL | Home phone: (+351) (1) 640767 - If all men were brothers, would you let one marry your sister ? ------------------------------ Date: 9 Apr 91 22:47:38 GMT From: usc!samsung!munnari.oz.au!yoyo.aarnet.edu.au!sirius.ucs.adelaide.edu.au!levels!etssp@ucsd.edu Subject: Farmers Storm NASA Tracking Station in Australia The Advertiser, Monday, April 8, 1991, p.1 writes [comments in square brackets are my own] WA [Western Australian] FARMERS STORM US SPACE BASE Perth: Angry WA wheat farmers stormed a United States tracking station yesterday to protest over American wheat subsidies and warned that more radical action would follow. About 100 farmers used chains and tractors to force their way into the Yaragadee tracking station, near Mingenew, 500 km north of Perth, before dumping truck loads of wheat. Once inside they chained up machinery, painted slogans on a number of US trucks and buildings, and used used a facsimile machine to send a strongly worded message to the Prime Minister, Mr. Hawke. ... The unmanned tracking station - used by the National Aeronautical and Space Administration (NASA) to track its space shuttles - is protected only by a cyclone fence. ... [Just to fill you in, Australian wheat is currently not subsidised by the the government and the farmers are seeking subsidies due to losses in sale caused by the American wheat subsidies] [Disclaimer: I have absolutely no connection with these farmers] -- Steven Pietrobon, Australian Space Centre for Signal Processing School of Electronic Engineering, University of South Australia The Levels, SA 5095, Australia. steven@rex.sait.edu.au ------------------------------ Date: 9 Apr 91 14:09:21 GMT From: usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!wa4mei!ke4zv!gary@apple.com (Gary Coffman) Subject: Re: Laser launchers In article <1991Apr5.180807.2593@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: > >It depends on the size of your payload. A system to lift manned spacecraft >would require gigawatt lasers, well beyond the current state of the art. >If you're willing to settle for 20kg per shot, the laser is still big but >is the sort of thing that could reasonably be built as a custom job today. >Funding is a much bigger problem than technology. Even to place a 20 kg payload in orbit would be quite a trick. The only laser technology capable of sufficient power is the gas dynamic laser. If you think the turbopumps on the shuttle main engines are a nightmare, you should consider the ones needed for a laser launcher. Lasers in general are very inefficient with less than ten percent of their input power delivered as usable energy in the beam. It would take at least 100 times as much fuel to power such a laser as would be required by a chemical rocket to launch the same payload. And that's if laser launching is even possible. The adaptive optics required to deal with the problem of atmospheric blooming while handling the enormous power of the beam are beyond the current state of the art. The cooling systems for the optics alone would be enormous. The control systems to drive the optics and control the laser haven't been designed, and system control for such a system is much tougher than most folks imagine. The major flaw of laser launchers is that they have to deliver all of the power necessary to orbit a payload through the thick lower atmosphere for the entire boost phase. This incurs a terrible efficiency penalty as well as being incredibly loud. Another technique discussed here recently is the railgun. While this system is feasible for specialized payloads, it has it's own set of drawbacks. First, it's only suitable for rugged payloads, large solar arrays are out. Second, there is a substantial mass penalty due to the required heavy structural components and the heat shield. Third, there are serious restrictions on the configuration of the payload due to the necessity of maintaining a high ballistic coefficent. And talk about loud, the hypersonic shockwave would be an enviornmental disaster. Both railgun and laser launched payloads will require sophisticated active guidance systems to achieve anything but a random orbit. In my view, these technologies are orders of magnitude more complex than even the shuttle. Like the chimera of controlled nuclear fusion, they are unlikely to deliver any useful results even after hundreds of billions of dollars and decades of effort are expended on them. Big dumb boosters, small clever rockets like Pegasus, and eventually, direct to orbit aerospace planes are much more likely to be sucessful at delivering payloads to orbit economically and in a realistic timeframe. Gary ------------------------------ Date: 9 Apr 91 19:01:14 GMT From: salt.acc.com!opal!art@apple.com (Art Berggreen) Subject: Re: Space technology In article nb0x+@andrew.cmu.edu (Nick A. Bucci) writes: > > I recently got into a "discussion" (argument is a better term) with >my father about the need for a space program. Being an old fashioned, >middle class, construction worker, he disagrees with the concept of >spending "a lot of money for nothing." I tried to show him how our >lives have benifited directly from space exploration: New products, new >technology, etc., but he remains unconvinced. > I would greatly appreciate any list of products, etc., that came as >a direct result of the Space program (both U.S. & international). Maybe >if I give him enough tangible evidence, I can win him over. > Also, let me know if I should post a comprehensive list as one is >formed. I apoligize in advance for any errors, I'll just list what I'm >given, though I'd appreciate feedback on the list so I can correct any >mistakes. > Thanks in advance. > -Nick A.Bucci I feel that it's pretty hard to separate the space program from the entire technological infrastructure of our modern society. Each technology tends to support the development of the others. Also, don't concentrate just on the manned space program, a lot of technology has been developed from the nonmanned sector. It's also hard to remember exactly how things used to be before the development of technology that we now take for granted. As for the cost, all of those dollars are not floating around in space, they filtered down to a lot of folks through primary, secondary, etc. jobs and were a significant piece of our economy. I'd just as soon have my tax dollars go to these kinds of national efforts than many of the ways the government has discovered to spend money. As for specifics, I think the biggest benefits are hard to see because they are part of our everyday lives rather than being a few specific items. (Yeah some people point to things like Corning-Ware, Teflon, etc.) But let's look at things like our communications infrastructure. We surely wouldn't have immediate access to world-wide, instantaneous news (if that's really good ;->), the wealth of cable TV programming or the kinds of international telephone service. It's been stated that much of the modern biomedical monitoring devices came directly as a result of the space program. For all we think of weather forcasts, things like torneado warnings and hurricane warnings would not be as good as they are today. Just a few ramblings.... Art ------------------------------ Date: 9 Apr 91 19:42:33 GMT From: okunewck@psuvax1.cs.psu.edu (Phil OKunewick) Subject: Re: Space technology art@opalacc.com (Art Berggreen) writes: >I feel that it's pretty hard to separate the space program from the entire >technological infrastructure of our modern society. Each technology tends >to support the development of the others. Also, don't concentrate just on >the manned space program, a lot of technology has been developed from the >nonmanned sector. It's also hard to remember exactly how things used to be >before the development of technology that we now take for granted. If I remember my childhood and history classes right, the U.S. was highly intimidated by the USSR putting Sputnik into orbit. In response, and partly to get one up on the Soviets, it was decided that "We can put a man on the moon in this decade." One way to get public support for the program was to paint these daredevels and test pilots as heroes, and televise every significant achievement. And it worked - the public _loved_ the space shots. Allocating a considerable percentage of our national budget was no problem. So, the initial goal of the U.S. space program was manned. Could one conclude that the U.S. unmanned space ventures were spinoffs of the manned space program; therefore all spinoffs are from the manned program? (This cause-and-effect technology stuff is _so_ complicated...) ------------------------------ Date: 10 Apr 91 01:03:32 GMT From: agate!headcrash.Berkeley.EDU!gwh@ucbvax.Berkeley.EDU (George William Herbert) Subject: Qeustion: OSC's Engineering Dpt. Address The subject says it all... I need to talk to someone in Orbital Sciences Corp's engineering department (I need some specs on Pegasus), and all I've got is their marketing dpt's address (who aren't very helpful...). Mail/address is preferred. Thanks, -george william herbert gwh@ocf.berkeley.edu ------------------------------ Date: 10 Apr 91 01:48:42 GMT From: agate!headcrash.Berkeley.EDU!gwh@ucbvax.Berkeley.EDU (George William Herbert) Subject: Re: spacesuits (Was: Re: HST in-orbit Maintenance) In article dlbres10@pc.usl.edu (Fraering Philip) writes: >Better spacesuits would help your idea and many others as well. >Any ideas? Better spacesuits are being worked on. NASA's funding prioririties, however, aren't geared towards actually building the new suit ideas. Both Johnson SC and Ames groups have demonstrated technology (soft and hard suits respectively) that would make great space station suits, but it seems like there's only enough money to rerate the Shuttle suit to 8 PSI (no prebreathe...). sigh. [of course, the Mars Spacesuit group is well underway...right on schedule for our predicted 2020ish launch 8-) but that's a different story...] == George William Herbert == * UNIX ate my last .sig, Waiting for Plan 9! * == JOAT for Hire: Anything, == ######### I do Naval Architecture, ########## ===+++ Anywhere, my price +++=== # Spacecraft Design, UNIX Systems Consulting # == gwh@ocf.berkeley.edu == # RPG writing/development, and lots of other # == gwh@gnu.ai.mit.edu == ## random stuff, of course. I'm a JOAT 8-) ## ------------------------------ Date: 9 Apr 91 16:15:49 GMT From: usc!snorkelwacker.mit.edu!thunder.mcrcim.mcgill.edu!bonnie.concordia.ca!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: Launch Technology: In article heskett@titan.tsd.arlut.utexas.edu (Donald Heskett) writes: >... This was achieved with near-satanic propellant combination of >lithium, fluorine and hydrogen. Does anyone know if any further work >was ever done with this propellant combination? I don't think so. There was a little bit of work done in the 60s on the slightly more mundane hydrogen-fluorine rockets, but it too went on the back burner when hydrogen-oxygen was picked for the Saturns. And all serious advanced propulsion work died in the post-Apollo cutbacks. This one doesn't sound very promising to me anyway. Mixing two liquids and one solid is not simple, and when two out of three of them have nasty handling problems, the result is likely to stay a lab curiosity. Even hydrogen-fluorine was judged to be in that category when the Saturn planning was being done: between handling problems, exhaust toxicity, and the primitive state of engine development, the performance advantage over hydrogen-oxygen wasn't thought worthwhile. -- "The stories one hears about putting up | Henry Spencer @ U of Toronto Zoology SunOS 4.1.1 are all true." -D. Harrison| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 9 Apr 91 19:45:48 GMT From: brody@eos.arc.nasa.gov (Adam R. Brody) Subject: back-up crews Since they abolished back-up crews since STS 4, what is the plan if someone gets sick or for some reason cannont make the flight? How long before the flight do the crew go into quarantine to prevent catching someone's cold or the flu? ------------------------------ End of SPACE Digest V13 #384 *******************