Date: Thu, 10 Dec 92 05:04:06 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #527 To: Space Digest Readers Precedence: bulk Space Digest Thu, 10 Dec 92 Volume 15 : Issue 527 Today's Topics: anniversary Another Orbit Question Earth Movie (2 msgs) Limbaugh Found Not Guilty (was: ...DoD hoax!) Lunar flight NASA TOWN MEETING NOTES Orbit Question? Pop in space Rush Limbaugh says problems with HST are a DoD hoax! Soaring like and Eagle (was Re: Range Safety and DC-X) stationary orbits over the poles STS-48 and "SDI": Oberg vs. Hoagland Terminal Velocity of DCX? (was Re: Shuttle ...) Voyager Icon Weekly reminder for Frequently Asked Questions list what the little bird told Henry Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 8 Dec 92 18:40:54 GMT From: Bruce Watson Subject: anniversary Newsgroups: sci.space In article <1992Dec7.222345.19868@Princeton.EDU| carlosn@luma.Princeton.EDU.ampr.org writes: |In article |-Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry | |... And to think that some of us were only months old when that happened. And |we will be very lucky if we see it happen again before we reach our forties. ^^^^^^^ Optimism is alive and well on the Net! -- Bruce Watson (wats@scicom) Bulletin 629-49 Item 6700 Extract 75,131 ------------------------------ Date: 8 Dec 92 23:30:52 From: Craig Powderkeg DeForest Subject: Another Orbit Question Newsgroups: sci.space In article hdgarner@acs.harding.edu writes: In article , zowie@daedalus.stanford.edu (me!) writes: >In article gary@ke4zv.uucp (Gary Coffman) writes: > In article hdgarner@acs.harding.edu writes: > >... Is it possible to keep a body at ... > >the same point say about 20000 or so miles above [a pole] of the earth? > [no.] >At an altitude of 20,000 miles above the surface, you'd only weigh about >1/25 of your surface weight due to the r-squared falloff in the g field. >But [still no.] I can see how a liquid fueled body could not remain in a stationary polar position for very long, but what about if instead of liquid fueled thrusters the body was equipped with ion thrusters and a solar array to power them. The solar array would be positioned so that it faced the sun at all times. Any thoughts? The problem is that you still need to throw away reaction mass. A rocket engine's propellant efficiency is measured in a weird unit called `specific impulse', measured in seconds. The specific impulse of an engine type is essentially the length of time an arbitrarily large craft (ie mass of propellant >> mass of craft) can support its full fueled weight in a 1g field, using that type of engine. [note that the actual maximum amount of hovering time would be longer, as the craft gets lighter when it ejects propellant, so there's less to support as time goes on] The more kinetic energy you shove into the propellant on the way out the nozzle, the more momentum you're also sticking into it. This means that, with more energy per unit propellant, you can hover longer, because you don't need to use as much of it, to dump the same amount of momentum. Chemical rockets, which use the propellant as fuel, are limited by the amount of energy you can stuff into a chemical bond. The theoretical maximum energy release per molecule of fuel/propellant is for [someone correct me if I botch it] a hydrogen-fluorine reaction, and it yields a specific impulse on the order of a few hundred seconds (maybe 350?). Nuclear engines (which use a nuclear reactor to heat the propellant) can do much better, since there's roughly a million times more available energy per atom of nuclear fuel, than per atom of chemical fuel. Existing designs (NERVA) get between 400s and 600s, if I recall right. Ion engines can do better, because they can use an external or non-chemical energy source. (There *is* a problem with calculating Isp for very high-impulse solar ion engines, because you have to account for the mass of the solar panels, which is more or less linear in the amount of thrust you need...) I don't remember figures for current ion engines offhand, but we can guess that they're between 1,000 and 10,000 seconds. Another serious problem is that this efficiency comes at a very low thrust -- but, for the sake of argument, let's assume a high-thrust, lightweight ion engine can be made, with comparable Isp. Assuming the payload mass is roughly the same as the fuel mass, we can estimate the maximum hover time as roughly twice the Isp, adjusted for local gravity. We find that the maximum hover time is roughly 50,000 to 500,000 seconds -- from about 12 hours to five days. That's a long time, but it's just not long enough to be worthwhile; you'd need to be supporting the payload for a minimum of months, preferably years. [Note that, in principle, you could do it with a Lofstrom loop or similar dynamic structure -- in effect, recycling the propellant. In a Lofstrom loop, you have a *really* *long* bicycle chain. You throw links up, *really* *fast*, from a ground station. They fly up to the height of the payload, and would go higher, except that they hit the bottom of the payload and are deflected down, depositing their momentum in it. Then they fall all the way to the ground station, where they are thrown up again. Because they're a continuous chain, they go right down to the ground station. As long as the ground station keeps throwing 'em back up, the whole thing works.] -- DON'T DRINK SOAP! DILUTE DILUTE! OK! ------------------------------ Date: 8 Dec 92 21:05:36 GMT From: Curtis Roelle Subject: Earth Movie Newsgroups: alt.sci.planetary,sci.space In article <1992Dec8.131618.13405@aio.jsc.nasa.gov>, tes@gothamcity.uucp (Thomas E. Smith [LORAL]) writes... >I have another question that maybe Ron Baalke can answer. Is Galileo going to >take any footage of the lunar eclipse tomorrow? I think that would be an awesome >short movie, and a once in a lifetime chance. What would be the point? The best seats for that are right here on earth, anywhere on the hemisphere from which the eclipse is visible -- no need for a billion-dollar space ship or awful false-colored imagery (but please don't tell congress all it takes is a $30 pair of binoculars 8-). ------------------------------ Date: 9 Dec 92 14:13:08 GMT From: David Toland Subject: Earth Movie Newsgroups: alt.sci.planetary,sci.space In article <1992Dec8.131618.13405@aio.jsc.nasa.gov>, tes@gothamcity.uucp (Thomas E. Smith [LORAL]) writes... >I have another question that maybe Ron Baalke can answer. Is Galileo going to >take any footage of the lunar eclipse tomorrow? I think that would be an awesome >short movie, and a once in a lifetime chance. Too bad it's not a solar eclipse. Footage of the moon's shadow crossing the earth's surface would really be striking! -- -------------------------------------------------------------------------- All opinions are MINE MINE MINE, and not necessarily anyone else's. det@phlan.sw.stratus.com | "Laddie, you'll be needin' something to wash | that doon with." ------------------------------ Date: 8 Dec 92 18:01:32 GMT From: Curtis Roelle Subject: Limbaugh Found Not Guilty (was: ...DoD hoax!) Newsgroups: sci.space Robert.Dyess@f6507.n124.z1.fidonet.org (Robert Dyess) writes: >>>rkornilo@nyx.cs.du.edu (Ryan Korniloff) writes: >>> >>> The popular American radio personality Rush Limbaugh stated today that >>>the problems with HSTs mirror are a Department of Defense hoax. He >>>says that the DoD took over control of the HST program so they could study >>>a strange radio source that could possibly be another civilization's radio >>> emmisions. And that the DoD cooked up the story of the faulted mirror to >>> cover up there actions. >>> Rush has over 13 million listeners and has may connections into the >>>goings ons of many behind-the-scenes happenings. I don't think that he >>>would make such a statment without a reason to believe it is true. >> If anybody would have listened clostly to what he said, they wouldn't >>make statements like this. He said specifically that this was a rumor that >>was going around (indeed, I heard it here on the net several days before he >>said it) and, although he didn't like to report rumors, he thought this one >>was funny enough to talk about. ONLY AFTER SAYING ALL THIS did he "report" >>the rumor. >> >> He never said that he thought it was true, nor did he say >>that he had any sort of (whisper here) inside story. Keep in mind that >>the man considers himself a humorist, albeit a conservative one. >Thanks for clearing this one up. I hadn't heard the radio show, but >Ryan's message sounded out of character for Rush Limbaugh. >The interesting phenomenon has been the way in which so many intelligent >people can be brought to a boil over a message posted by one person who >made an error. I've been reading this Newsgroup daily and as far as I can >tell, all of the heated discussion about how stupid Rush is can be traced >back to Ryan's message quoted above. Incredible isn't it. :-) Just think how often the press takes a snippet quote from a scientific figure and starts a feeding frenzy (When is it that S-T will extinct earth?). How is this situation different? Isn't this just the same outrageous occurrance in reverse? Limbaugh, a figure from the press says something and someone from the usenet hears a segment while listening to his car radio during the lunch hour. Next it gets posted out of context to sci.space starting a rabid cascade by people who even admit having never heard the program! Using one rumor used to start another rumor. How embarrassing! Curt Roelle ------------------------------ Date: 9 Dec 1992 11:10:42 GMT From: Jeffrey Alan Foust Subject: Lunar flight Newsgroups: sci.space In article David.Anderman@ofa123.fidonet.org writes: >Inquiring minds want to know: >A Soyuz capsule costs about $7 million, and has a mass of 7 tons. >The new Proton KM launcher (due in 1995) will cost about $30 million, >and be able to send 7.5 tons in a lunar trajectory. > >Why isn't there talk of a circumlunar flight, paid for by the USA, and crewed >with US astronauts? We could send US astronauts around the poles of the moon >during the Clinton Administrations' first term...... > I've been tossing this concept through my mind the last few days as I slogged through finals, and came up with this idea: instead of having the US or some other government fund a circumlunar mission as described above, have a coalition of corporations and/or foundations provide the funding. At these costs (or even costs a few times higher) it seems to be in the range of corporations and well-endowed foundations to foot the bill for a mission. One scenario that comes to mind would be to create a non-profit corporation to oversee the creation and execution of such a mission (lining up the Russian Proton and Soyuz capsules, finding the funding in the US and elsewhere, running a full-tilt PR program to get people excited about the mission, etc.). Crew selection would probably also be handled by this organization, although this might be trickier (who decides who is qualified for such a mission?), although at least broad decisions on the crew makeup would be possible (i.e., is the crew international or all from one nation). The amount of science you could do on a such a mission is a subject for debate, but the real goal for such a mission would be to get people, both the general public and ranking individuals in governments and corporations, energized to work on a permanent return to the moon. Such a flight might be basically a publicity stunt, but it may very well be what's needed to get people really thinking about and committed to a full scale return to the moon. -- Jeff Foust Senior, Geophysics/Planetary Science, Caltech jafoust@cco.caltech.edu jeff@scn1.jpl.nasa.gov Tom Seaver: "Hey, Yogi, what time is it?" Yogi Berra: "You mean now?" ------------------------------ Date: Wed, 09 Dec 92 15:52:04 PST From: Richard Buenneke Subject: NASA TOWN MEETING NOTES The following is a write-up of Goldin's presentation at the Dec. 3 NASA Town Meeting in L.A. I'd be interested in reports on subsequent meetings. I think one was scheduled for Seattle this week or next week. - --------------------------------------- GOLDIN CALLS FOR CULTURAL CHANGES AT NASA CARSON -- The entire civil space program must undergo a major cultural change to become more than a "white collar jobs program," says NASA Administrator Daniel Goldin. "It's going to take three to five years to change a culture," Goldin told a NASA town meeting. Goldin said the agency's work on cutting edge technology will grow in an era of defense cutbacks. "[In many areas], the last remaining hope to maintain some capacity of the aerospace industry is our civil space program." With the end of the Cold War, NASA must move beyond a culture based on "big science" projects. Instead, the space agency needs to find better ways to transfer technology to industry and to improve U.S. math and science education. The nature of the geo-political changes was evident at the town meeting. Before fielding questions, Goldin invited his Russian counterpart, Yuri Koptev to speak. The Russian Space Agency director was amazed at the spectacle of a space official touring the hustings to justify his budget. "For the past 35 years, we have had other rules in my country." Although the civil space program has enjoyed funding increases in recent years, Goldin said the days of growing budgets are over. "Right now, Americans are introspective and uncertain," he told a session at the Dominguez Hills campus of California State University. NASA needs to move away from a culture based on minimizing risks and avoiding accountability. "You can't paperwork in good engineering." Goldin emphasized that the challenge extends beyond the government. When a Hughes Aircraft engineer said Goldin's changes were just what his colleagues had discussed among themselves over coffee, Goldin retorted that the engineer's attitude was part of the problem. "All you folks sit around drinking coffee saying, 'What's going to happen now?'" Goldin said. Industry also must overcome the "sickness" of passivity and encourage initiative. "America is afraid of being bold. We've replaced risk with paperwork." The willingness to accept risk also applies to space scientists. Noting that only two science payloads are under development, Goldin said the program was following "Augustine's Law." Devised by Martin Marietta chairman Norman Augustine, this law notes that increasing system complexity is matched by smaller total purchases. As the space science program converges towards one payload, a mission becomes the only opportunity for experiments. As these Big Science programs become linked to national prestige, the space agency becomes more conservative in program management. Although this conservatism only delays science, Goldin said space scientists react "like stuck pigs" to proposals for smaller, single sensor payloads. The National Aeronautics and Space Administration also plans to take the first part of its name seriously. Goldin acknowledged that he once questioned why the agency was involved in aeronautics research. "I asked, 'Who is our customer?," he said. But reviews of the program -- only 17% of the agency's total budget -- convinced him of the need to continue aircraft research. "The aeronautics industry is hurting powerfully bad." To make NASA's dollars go farther, Goldin said the space agency must do more to exploit cutting edge technology. "If NASA works on 10-year-old technology, it becomes a jobs program." Whether Goldin will be able to see these changes through remains an open question. Although he's a registered Democrat, the former TRW executive is a Republican appointee. For now, President-elect Bill Clinton and Vice President-elect Al Gore Jr. are saying little about their plans for space. The leader of space transition issues, former astronaut Sally Ride, had little time for the Bush administration's space agenda. While Ride isn't commenting on her work, other Clinton-Gore space advisers support Goldin's efforts to reform NASA. The strength of Goldin's commitment to reform was visible at the town meeting. The session was the fourth in a series of six meetings held around the country. The town meetings are part of Goldin's effort to reach beyond NASA's iron triangle of Congress, field centers and space contractors. "We picked places to go where NASA was not," he said. This outreach will help NASA diversify its technical work force beyond its traditional base of white, male engineers. ------- End of Forwarded Message ------------------------------ Date: 8 Dec 92 18:26:37 GMT From: Bruce Watson Subject: Orbit Question? Newsgroups: sci.space In article Subject: Pop in space Newsgroups: sci.space In <1992Dec4.164414.22027@elroy.jpl.nasa.gov> pjs@euclid.JPL.NASA.GOV (Peter J. Scott) writes: >In article <1992Dec4.115140.7908@syma.sussex.ac.uk>, torh@syma.sussex.ac.uk (Tor Houghton) writes: >> I don't know - didn't Coke or Pepsi device special cans for the Space >> Shuttle crew? :) >Yes, and you can see the Coke device in the Coca-Cola museum in >Atlanta, GA. I know it's a tad far for you to go, but some of >our other readers might be nearby. I've seen it, really high-tech. I looks like one of those old portable PC's. It has a screen and some other really weird hardware. Now I have faith that my tax dollars are really going to a good cause. -- Charles Stephens cfs@cowpas.waffle.atl.ga.us ------------------------------ From: Curtis Roelle Subject: Rush Limbaugh says problems with HST are a DoD hoax! Newsgroups: sci.space Organization: Johns Hopkins University References: <723626109.F00001@ocitor.fidonet> Date: 8 Dec 92 17:28:33 GMT Lines: 18 Source-Info: Sender is really news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU Robert.Dyess@f6507.n124.z1.fidonet.org (Robert Dyess) writes: >The interesting phenomenon has been the way in which so many intelligent >people can be brought to a boil over a message posted by one person who >made an error. I've been reading this Newsgroup daily and as far as I can >tell, all of the heated discussion about how stupid Rush is can be traced >back to Ryan's message quoted above. Incredible isn't it. :-) Just think how often the press takes a snippet quote from a scientific figure and starts a feeding frenzy (When is it that S-T will extinct earth?). How is this situation different? Isn't this just the same outrageous occurrance in reverse? Limbaugh, a figure from the press says something and someone from sci.space hears a few words listening to his car radio during his lunch hour. Next it gets posted out of context starting a rabid cascade by people who admit having never heard the program! How embarassing. Curt Roelle ------------------------------ Date: 9 Dec 92 13:31:40 GMT From: Gary Coffman Subject: Soaring like and Eagle (was Re: Range Safety and DC-X) Newsgroups: sci.space In article <1992Dec7.162938.1@fnalo.fnal.gov> higgins@fnalo.fnal.gov (Bill Higgins-- Beam Jockey) writes: >In article <1992Dec7.164541.2299@ke4zv.uucp>, gary@ke4zv.uucp (Gary Coffman) writes: >> Let's hope it flies like a Pheonix, rising gracefully out of it's own flames. >> It certainly can't soar like an Eagle. :-) > >Oh, I don't know, Gary. The thrust-to-weight ratio on DC-X probably >compares favorably with an F-15 Eagle... Yeah, but an Eagle has "wangs" (such as they are). :-) Gary ------------------------------ Date: Wed, 09 Dec 92 18:01:04 EST From: Tom <18084TM@msu.edu> Subject: stationary orbits over the poles hdgarner@acs.harding.edu writes: [what about holding them there with ion thrusters powered by sunlight?] Josh sez: >Ion thrusters still require fuel their just much more efficient than chemical >rockets. The only system that can stay stationary over long terms is a solar >sail. Nature may permit some neat tricks with magnetodynamic tethers but I >can't think of any that would work in this situation. For the poles, forget about tethers. What you want is some kind of giant charged ring that you use sunlight to spin, creating a force from the magnetic field of the Earth that balances gravity. It can also be solar powered. "Only one, really BIG moving part!" It has incredible stability and power requirements, but at least you lose the need for reaction mass, which is the big problem with the other kind of stationary satellite. Actually, you can cut power requirments by using a giant wire, and just pump a bazillion amps through it (I haven't worked out the math :-) The force/mass-unit is the same, but the mass would be a lot less. You could have two wires, with currrent running in opposite directions. The first would be your "power ring", while the second would be "Vertical postioning". Keeping it on the axis would be a trick, though, since the shape of the Earth's field would create a positive instability. -Tommy Mac -----------------------------============================================ Tom McWilliams | What a tangled web we weave, when at ". | 18084tm@ibm.cl.msu.edu | , .first we .practice .*' .| (517) 355-2178 -or- 353-2986| '. ' . . to decieve , | a scrub Astronomy undergrad | After that, the , + | at Michigan State University| improvement is tremendous! '. , .' | ------------------------------=========================================== ------------------------------ Date: Wed, 9 Dec 92 12:18:11 GMT From: Dean Adams Subject: STS-48 and "SDI": Oberg vs. Hoagland Newsgroups: sci.skeptic,sci.astro,sci.space,alt.alien.visitors sgamble@crc.ac.uk (Steve Gamble x3293) writes: >Does the fact that Robert Sheaffer is a member of CSICOP and James Oberg >is a friend of his and they both know Phil Klass mean that their solution >to the video is incorrect? Some do think that way. Personally, I have to think that anyone who could call what is obviously TINY ice particles a "UFO" is sadly about absolute epitome of a completely ignorant "ufo-nut". The same people also called the insulation/debris ejected during the last TDRS deploy a "UFO" as well, and once again the Shuttle was being "attacked by aliens"... I watch (and tape) countless hours of live coverage from every Shuttle mission, and when people who would not know a water dump from a water closet start seeing "aliens" everywhere it just makes me sick. >I am happy that Oberg's explanation fits with what is shown on the video. >The UFOs and the missile which shoots them down Oh, brother! With examples like this how are people supposed to ever take *ANY* "sightings" reports at ALL seriously?? >are nothing other than small debris close to the camera, probably ice >crystals. The change in motion is caused by the firing of a thruster >just out of camera shot. EXACTLY, and to anyone at all familar with space or the Space Shuttle, that is an almost immediate thing to see. It's very plain. It took really wild imagination to dream up that "missile" (??) nonsense. ------------------------------ Date: 9 Dec 92 13:30:30 GMT From: Gary Coffman Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space In article <1992Dec7.194132.19219@wuecl.wustl.edu> gene@wucs1.wustl.edu (_Floor_) writes: >In article <1992Dec5.165219.18302@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >] always mean higher reliability. A truck engine is usually good for >] a million miles while a formula one engine may last 100. They both >] put out roughly the same amount of power, but one masses a lot more >] than the other. >] > >What?!? What kind of a comparison is that? I don't really think this is >an appropriate example of your point. A formula one engine is tortured >by blipping rapidly back and forth between 3,000 and 13,000 rpm continually >for two hours. It isn't the size that's the factor, is the use! I think >a tree trunk versus a twig is a better example of your scale/reliability >dependence point. Actually, both engines have narrow torque bands. Thanks to multi-speed gearboxes, both engines are kept near their torque peak at all times in service. The RPM levels are grossly different, 1800 for the truck and 12,500 for the F1 engine. That's because the smaller engine has to wind tighter to make the same power. IE it's stressed harder because it has to be small to maintain an acceptable mass ratio in a race car. Power to weight ratios are critical to good race car performance as they are to good SSTO performance, and for the same reason. Light high output engines are less reliable than heavy high output engines. The margins are thiner in the racecar than the truck. The truck can afford to throw away a couple of thousand pounds of payload for a more reliable engine, the race car cannot. An SSTO has to haul all of it's engine and structure mass to orbit so these have to be lighter than a staged rocket that can discard engines and structure along the way. This is inherent in SSTO design. So a staged rocket can be made to have lower stresses than a SSTO for the same payload. Shuttle is only high stress because it emphasizes large payload in what is essentially a 1.5 stage design. Thus the SSME have to push much harder than they otherwise would have to. With a 2 or 2.5 stage design, the engines could operate at lower stress levels since they would be pushing less dead weight. The wings impose a mass penalty, but that's offset by not having to carry landing fuel and it's tankage for VTOL operation. Gary ------------------------------ Date: Wed, 9 Dec 92 09:37:00 PST From: "UTADNX::UTDSSA::GREER"@utspan.span.nasa.gov Subject: Voyager Icon In Space Digest V15 #522, "Matt J. Martin" writes: > A friend of mine is looking for a printout of the DeVinchi "Man in Motion" >(or whatever the name of it is) that was printed on the side of the Voyager >probes (along with the gold record of the sounds of humanity and the other >memorabilia for any casual passers by to inspect.) Is this picture >on ftp somewhere? > > Thanks in advance, > ## // ## Matt J. Martin, Technosociology and Space Politics ## // ## > ## // ## Purdue University, West Lafayette, IN ## // ## > ## / ## myempire@mentor.cc.purdue.edu ## / ## Argh! Should I fear for our nation's future, or have young folks always been this ignorant? Leonardo DA VINCI's famous drawing never appeared on any space probes. As for finding a "printout" of the plaque that was affixed to the Voyagers, I'm sure your university has a LIBRARY. _____________ Dale M. Greer, whose opinions are not to be confused with those of the Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER Remember: Half of all people are of below average intelligence. ------------------------------ Date: 9 Dec 92 14:43:13 GMT From: Jon Leech Subject: Weekly reminder for Frequently Asked Questions list Newsgroups: sci.space,sci.astro,sci.space.shuttle This notice will be posted weekly in sci.space, sci.astro, and sci.space.shuttle. The Frequently Asked Questions (FAQ) list for sci.space and sci.astro is posted approximately monthly. It also covers many questions that come up on sci.space.shuttle (for shuttle launch dates, see below). The FAQ is posted with a long expiration date, so a copy may be in your news spool directory (look at old articles in sci.space). If not, here are two ways to get a copy without waiting for the next posting: (1) If your machine is on the Internet, it can be obtained by anonymous FTP from the SPACE archive at ames.arc.nasa.gov (128.102.18.3) in directory pub/SPACE/FAQ. (2) Otherwise, send email to 'archive-server@ames.arc.nasa.gov' containing the single line: help The archive server will return directions on how to use it. To get an index of files in the FAQ directory, send email containing the lines: send space FAQ/Index send space FAQ/faq1 Use these files as a guide to which other files to retrieve to answer your questions. Shuttle launch dates are posted by Ken Hollis periodically in sci.space.shuttle. A copy of his manifest is now available in the Ames archive in pub/SPACE/FAQ/manifest and may be requested from the email archive-server with 'send space FAQ/manifest'. Please get this document instead of posting requests for information on launches and landings. Do not post followups to this article; respond to the author. ------------------------------ Date: Wed, 9 Dec 92 12:09:21 -0600 From: pgf@srl03.cacs.usl.edu (Phil G. Fraering) Subject: what the little bird told Henry Begin partial excerpt: Crucial technology improvements over shuttle. Engine performance similar (not quite as good, but close) without staged combustion. GOX/GH2 reaction control system, Al-Li LOX tanks, graphite-epoxy LH2 tank, composite primary structures, ceramic composite thermal protection. NASP efforts demonstrate desired structural weight at greater loads and much higher temperatures. Structural materials already in use -- composites on ATF fighter prototypes, existing spacecraft (including Hubble); Al-Li on heavy cargo aircraft. ... DC thermal protection: carbon/silicon-carbide for nose and other hot spots (maneuvering flaps), multiwall construction with refractory alloys for most of fuselage, titanium on the lee side and the base. All temperatures below NASP and shuttle, well below material limits. END OF EXCERPT Hmm... every report that seems to come out says that the reason it's possible now is because of the NASP materials research. BUT: if the main place where NASP materials seem to be being used is the heat shielding, and its re-entry temperature is lower than the shuttle's, wouldn't shuttle re-entry materials be just as useful? Given the design margins below, I doubt that there would be any weight penalty... You may want to save this article, I'm about to say something good about the Shuttle: has anyone out there stopped and thought that the most criticized part of the shuttle program at its start, the heat shielding, has been giving little to no trouble, and in retrospect is behind the SRB's _and_ the SSME's _and_ aerodynamic problems of an unspecified sort (which is why the landing limit is 40K lbs.) in being a risk to astronaut's lives and the investment of money represented by the orbiters... In short, one good thing the shuttle did, that all reusable spacecraft following it can benefit from, (except for wierd design specs like NASP) is its pioneering use of the first reusable heat shield. Also, I've heard that the major problems in between-flights overhaul in the shuttle are the SSME's. While this doesn't neccesarily mean the tiles are good, it implies that they need less overhaul than the engines and aren't the source of headache and worry everyone said they would be at the start of the program. Or were before they found out about the scotch guard. What sort of overhauls do the tiles get? \Ample margins to reduce development risk. Design margins of 15% on dry /weight, 20% on T/W ratio while still preserving ample operational margin. Look, Gary! Weight margins! \"God willing... we shall return." | Henry Spencer @ U of Toronto Zoology / -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry -- Phil Fraering "...drag them, kicking and screaming, into the Century of the Fruitbat." <<- Terry Pratchett, _Reaper Man_ PGP key available if and when I ever get around to compiling PGP... ------------------------------ End of Space Digest Volume 15 : Issue 527 ------------------------------