Date: Thu, 21 Jan 93 05:12:52 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #068 To: Space Digest Readers Precedence: bulk Space Digest Thu, 21 Jan 93 Volume 16 : Issue 068 Today's Topics: "Synchronous Orbits around other planets" *** BUSSARD RAMSCOOP *** Adelaide Space Frontier Society Meetings A question about mercury and Gemini. (3 msgs) averting doom Earth's rotation rate may be due to early collisions [Release 93-12] (Forwarded) (2 msgs) Galileo Stuck Ribs / Remote Manipulator? Goldin's future (2 msgs) Great stuff at NASA and D. WINGO is "why we now" Let's be more specific (was: Stupid Shut Cost arguements) Lunar Rotation (was: Earth's rotation rate...) Shuttle safety margins Territorial conquest? Pishaw!! 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: Wed, 20 Jan 1993 21:01:17 GMT From: Larry Wall Subject: "Synchronous Orbits around other planets" Newsgroups: sci.space In article <1993Jan19.174259.12101@sunova.ssc.gov> faught@berserk.ssc.gov writes: : In article tombaker@world.std.com (Tom A Baker) : writes: : >Thousands of counterexamples exist if you are willing to consider SMALL : >bodies. You might find rocks, asteroids, that spin faster than their : >surface's orbital velocity, and remain held together by cohesion. A : >synchronous orbit would be impossible, exactly as you are asking. : : Never say never..... Simply tie the satellite to the body with a tether. Somehow it seems to be cheating to use the term satellite for such an object: "Sorry, hon, I can't do the dishes tonight--I've got to shinny down to Oscar 2931 and change the batteries." [I originally wrote "shinny up", but decided that was wrong...] Larry Wall lwall@netlabs.com ------------------------------ Date: 20 Jan 93 23:42:14 GMT From: Lynne K Wahl Subject: *** BUSSARD RAMSCOOP *** Newsgroups: sci.space uphrrmk@gemini.oscs.montana.edu (Jack Coyote) writes: >In sci.space, henry@zoo.toronto.edu (Henry Spencer) writes: >> [some really interesting stuff about fusion and radiation deleted] > More hazards/limits: > magnetic drag: The large magnetic field will have a (admittedly smaller) > interaction with the (unmapped) interstellar magnetic field. > dust: Non-magnetic & relativistic (ouch) > Bok globules: Blobs of cold dark gas. Rich in hydrogen, but the rapid rise > in density is problematic to a ramscoop. > etc. > Sorry, few solutions, just more problems. > Note to flamers: I LIKE the idea, it just needs work. The best way to solve > the above requires that people know about them. They haven't > been mentioned (that I have seen), so I did. >-- >"Pound for pound, lame puns are your best entertainment value." -- Gogo Dodo Hmmm... This sounds like an interstellar probe is needed to collect information before a *really* fast spacecraft is launched. How about a .01c speed probe with a small "sail" that would be primarily used to collect interstellar H (for testing) and with magnetic sensors to check on the magnetic medium as it goes. How far from the sun would this "Pathfinder" type of probe need to go before getting outside the sun's environment? As an exercise, how fast would, say a refueled shuttle ET, one SSME, and a 30 ton probe go if launched in a "generic" solar escape orbit? ($)(0000000)< Probe=($) Space Shuttle Main Engine= < External Tank=(0000000) With a little money, and a Single Stage to Orbit shuttle (for refueling the ET) this could be (launched? boosted?) by 1997. -- --Lynn Wahl lwahl@matt.ksu.ksu.edu | The meek will inherit the Kansas State University Student | earth, the rest of us are Soil Conservation Service Computer Specialist | going to the stars. ----* ------------------------------ Date: 20 Jan 93 02:54:36 GMT From: etssp@levels.unisa.edu.au Subject: Adelaide Space Frontier Society Meetings Newsgroups: sci.space The following meetings of the Adelaide Space Frontier Society (a Chapter of the National Space Society of Australia) are scheduled on Wednesday's of each month at 8:00 pm in Tutorial Room 1-16 Signal Processing Research Institute University of South Australia The Levels SA 5095 17 February A talk from John Douglas on S.A. Government role in space. 17 March A talk by John Dunkley on satellites. 21 April A talk from Ian Tuohy from BAAe on Southern Launch Vehicle. 19 May Paul Arthur to talk on GPS from Auspace Ltd. 16 June A talk by Evan Semple on Single Stage to Orbit. 21 July Jane Brooks to give a slide show on the Smithsonian Institution National Air and Space Museum. 18 August Space videos. 15 September Dean Hodgson to talk on Moon race. 20 October Craig Robinson to talk on CNES, French Space Agency. 17 November A talk by Mark Blair on AUSROC II-02. 8 December AGM and elections of ASFS officers. -- Steven S. Pietrobon, Australian Space Centre for Signal Processing Signal Processing Research Institute, University of South Australia The Levels, SA 5095, Australia. steven@spri.levels.unisa.edu.au ------------------------------ Date: 20 Jan 93 19:02:59 GMT From: fred j mccall 575-3539 Subject: A question about mercury and Gemini. Newsgroups: sci.space In article <1jc7ljINNagm@mirror.digex.com> prb@access.digex.com (Pat) writes: > >During the mercury and gemini program, we had very little experience >in the developement of rockets, capsules, engines, etc. In fact >mercury had a number of troubles with the main boosters. > >Now these systems had escape rocket towers for abort safety, but >they would be jettisoned 1-2 minutes into flight. My question, >is if you have already paid the penalty, to carry the tower, >why not keep it as an emergency retro-rocket, in case the main >retro-roket failed? granted the performance of the escape >tower would have to be improved to match the main package, >but were teh retros already fail-safe? seems like they were >awful sure. Well, I can't say for certain, but consider the speed the vehicle was moving when they jetison the tower as opposed to the speed it needed to achieve. I can imagine all sorts of possible aerodynamic problems as the speed of the vehicle increased. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 20 Jan 93 20:13:08 GMT From: Steve Derry Subject: A question about mercury and Gemini. Newsgroups: sci.space fred j mccall 575-3539 (mccall@mksol.dseg.ti.com) wrote: : In article <1jc7ljINNagm@mirror.digex.com> prb@access.digex.com (Pat) writes: : > : >During the mercury and gemini program, we had very little experience : >in the developement of rockets, capsules, engines, etc. In fact : >mercury had a number of troubles with the main boosters. : > : >Now these systems had escape rocket towers for abort safety, but : >they would be jettisoned 1-2 minutes into flight. My question, : >is if you have already paid the penalty, to carry the tower, : >why not keep it as an emergency retro-rocket, in case the main : >retro-roket failed? granted the performance of the escape : >tower would have to be improved to match the main package, : >but were teh retros already fail-safe? seems like they were : >awful sure. : Well, I can't say for certain, but consider the speed the vehicle was : moving when they jetison the tower as opposed to the speed it needed : to achieve. I can imagine all sorts of possible aerodynamic problems : as the speed of the vehicle increased. The sooner you can dispense with unneeded mass, the less fuel you expend accelerating that mass. The escape towers were undoubtedly jettisoned as early as possible in the mission -- as soon as they were no longer needed to escape a malfunctioning booster. Carrying those towers the whole way up to orbit would incur a substantially greater fuel penalty. By the way, Mercury and Apollo used escape towers; Gemini had ejection seats. -- Steve Derry ------------------------------ Date: 20 Jan 93 23:09:57 GMT From: Bob Pendleton Subject: A question about mercury and Gemini. Newsgroups: sci.space In article <1jc7ljINNagm@mirror.digex.com> prb@access.digex.com (Pat) writes: > >During the mercury and gemini program, we had very little experience >in the developement of rockets, capsules, engines, etc. In fact >mercury had a number of troubles with the main boosters. > >Now these systems had escape rocket towers for abort safety, but >they would be jettisoned 1-2 minutes into flight. My question, >is if you have already paid the penalty, to carry the tower, >why not keep it as an emergency retro-rocket, in case the main >retro-roket failed? granted the performance of the escape >tower would have to be improved to match the main package, >but were teh retros already fail-safe? seems like they were >awful sure. Gemini had an escape rocket tower? I was only a kid but I don't remember seeing one. The models I built of Gemini didn't have one. Mercury had an escape tower. Gemini may have been able to use its retro rockets to boost the capsule away from the booster. But I'm pretty sure it didn't have an escape rocket tower. Bob P. -- Bob Pendleton | As an engineer I hate to hear: bobp@hal.com | 1) You've earned an "I told you so." Speaking only for myself. | 2) Our customers don't do that. <<< Odin, after the well of Mimir. >>> ------------------------------ Date: 20 Jan 93 22:14:26 GMT From: Michael Robert Williams Subject: averting doom Newsgroups: sci.astro,sci.space,sci.physics,sci.environment In article <1javk0INNn7s@geraldo.cc.utexas.edu> wolfone@ccwf.cc.utexas.edu (Nobody of Importance) writes: >In article <93Jan17.053457.45192@acs.ucalgary.ca> jsbell@acs.ucalgary.ca (Joshua Bell) writes: >]In article <1993Jan13.225015.24673@stsci.edu> vener@stsci.edu (Patricia C. Vener-Saavedra) writes: >]>Hi there. As I recall, in about a billion years the sun will have >]>about twice the luminosity it presently has. The average surface of >]>Earth will be about 100 degrees C. Some lakes and rivers will have >]>begun to boil. It will not be pleasant for homo sapiens.:-) >] >]I would say that if Homo sapiens is still on Earth in a billion >]years, it deserves it. :) > Actually, for solar-sail proponents like myself, that's prime sailing weather! Twice the luminosity=twice the thrust. I think by then we should have a way to make 30nm thick aluminum sails with embedded control structures (unless, of course transportation has evolved to the *poof! You're there stage). In Real Life:Mike Williams | Perpetual Grad Student e-mail :mrw9e@virginia.edu| - It's not just a job, it's an indenture --------------------------------------------------------------------------- "If you ever have a world of your own, plan ahead- don't eat it." ST:TNG ------------------------------ Date: 20 Jan 93 19:44:26 GMT From: fred j mccall 575-3539 Subject: Earth's rotation rate may be due to early collisions [Release 93-12] (Forwarded) Newsgroups: sci.space In article <1993Jan18.210842.12714@hpcvca.cv.hp.com> rayd@hpcvcas.cv.hp.com (Ray Davis) writes: >> "A popular theory holds that the collision of a Mars-sized planetary body >> with the Earth threw considerable debris into orbit, which then came together >> to form the moon," Dones said. "Thus, the same impact which gave Earth its >> spin, could also have formed the moon." > >How does this popular theory account for the moon having zero spin? I don't think it has to. Tidal locking would would work independently of how the moon got where it is now, or so it seems to me. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 20 Jan 93 20:46:54 GMT From: Larry Wall Subject: Earth's rotation rate may be due to early collisions [Release 93-12] (Forwarded) Newsgroups: sci.space In article <33529@scicom.AlphaCDC.COM> wats@scicom.AlphaCDC.COM (Bruce Watson) writes: : In article <1993Jan18.210842.12714@hpcvca.cv.hp.com| rayd@hpcvcas.cv.hp.com (Ray Davis) writes: : || "A popular theory holds that the collision of a Mars-sized planetary : || body with the Earth threw considerable debris into orbit, which then came : || together to form the moon," Dones said. "Thus, the same impact which gave : || Earth its spin, could also have formed the moon." : | : |How does this popular theory account for the moon having zero spin? : | : The moon rotates once a month, otherwise it wouldn't keep the same : face to the earth. : : The "lock" occurred due to tidal friction and took a long time to happen. Nevertheless, I don't know of any evidence that Moon ever did have much of a spin (relative to the "lock"). The fact that the back side of the Moon is so different from the front side would tend to argue against it. But to answer what I believe to be the original question, the apparent inconsistency of a collision giving spin to the Earth but not to the Moon is resolved easily. The Earth and the Collider were already formed at the time. Since they were both sizeable, it's statistically likely (but not certain) that after the collision the Earth would be left with a significant spin, just as football player getting tackled is likely to have his attitude adjusted, so to speak. Now here's the key to the conundrum. The Collider, according to theory, *pulverized* both itself and a bunch of the Earth's crust and mantle, throwing lots of little rocks into orbit around Earth, but no Really Big Ones. These eventually accreted into the Moon. Since there's lots of little rocks coming from every which a way, however, it's statistically unlikely that the Moon would end up with a large residual spin, just as a football player doesn't expect to be suddenly upset by the air molecules that are pounding him constantly from every direction (in the absence of tornadoes). Now, in actual fact, I expect that there might be some small residual spin, perhaps because most of the rocks are going the same direction around the Earth, and the inner ones are going faster than the outer ones, making a sort of "wind" of rocks. Even football players have to take the wind into account upon occasion. But the general principle still holds to the first approximation. Statistics only works well with large samples. You're much more likely to be knocked down by a snowball than by an equivalent number of snowflakes. Larry Wall lwall@netlabs.com ------------------------------ Date: Wed, 20 Jan 1993 18:25:15 GMT From: fred j mccall 575-3539 Subject: Galileo Stuck Ribs / Remote Manipulator? Newsgroups: sci.space,sci.astro,alt.sci.planetary In article (Walt Sellers) writes: >In article , ahabig@bigbang.astro.indiana.edu (Alec Habig) writes: >> >.. >> >would it be to incorporate a robotic arm manipulator into these designs, >> >articulated so that it could reach everything on the probe/satellite? >> >> I think the big problem would be that this arm would be just as likely to get >> broken as any part that it might be able to fix. >> >If anything did break that the arm *could* fix, then it would be more than >sensible to bring it along, wouldn't it? Sure, but figure all the odds and then figure the opportunity cost of hauling along the weight of the arm on those occassions when nothing it could fix broke (instead of filling that space/weight with more instruments). Hey, I know. We could only include the arm on vehicles where we knew something it could fix was going ot break! ;-) -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 20 Jan 93 18:40:39 GMT From: Anita Cochran Subject: Goldin's future Newsgroups: sci.space,talk.politics.space In article <1jk1jmINN5vh@mirror.digex.com>, prb@access.digex.com (Pat) writes: > >In article hagen@owlnet.rice.edu (Jeffrey David Hagen) writes: > >>Besides, catch a clue about JPL. It is widely considered to be the single most > >>bloated, pig-headed, and inefficient part of NASA among industry folks I have > I am here in Washington DC, and mostly deal with NASA HQ and GOddard people. > The senior Scientist I met who was heavily involved in funding Planetary > Science programs (Name withheld due to confidence) Blamed JPL for the > cancellation of Magellans Cycle 4-5 imaging. His comments were that > JPL can't do mission support for under 50 million/year. > I couldn't let this pass, especially since you are ascribing it to someone anonymous. I have been involved the past few years with a National Research Council committee which evaluates current missions and works on future strategies. We are, technically, independent from NASA but do interact a great deal. We have discussed Magellan a great deal in this committee. First, last year when it was decided to terminate Magellan after cycle 4, Wes Huntress (then head of the Solar System Exploration Division) stated that he and Len Fisk made the decision since the mission had been baselined as a 1 cycle mission and it had accomplished more and the money was needed elsewhere. I am not privy to why exactly that money was needed but I trust Wes. He did make sure that cycle 4 was able to do the gravity mapping (including lowering the orbit some). I saw Wes again at one of these meetings last week. Wes is now head of Mission from Planet Earth (half of the Office of Space Science and Applications). Over dinner, I asked him about Magellan. He said that the transmitter on Magellan had gotten so balky that they were thrilled to get most everything they did manage to get at the end of cycle 3. He stated that it would have been impossible to get much imaging in cycle 4 due to this equipment problem. It is not the radar but the transmitter. He is one of the people who is pushing that there be an aerobraking experiment at the end of cycle 4 and, since he controls the purse strings, he is the one who can make this happen. Magellan is a great mission but apparently it does indeed have some problem which limits the radar now (anyone from the Magellan office care to comment). Wes feels badly the plug had to be pulled. Now, lets push for future missions. And yes, the political reality is that they have to be smaller than Cassini. There is still a lot to do. -- Anita Cochran uucp: !utastro!anita arpa: anita@astro.as.utexas.edu snail: Astronomy Dept., The Univ. of Texas, Austin, TX, 78712 at&t: (512) 471-1471 ------------------------------ Date: 20 Jan 93 17:52:25 GMT From: Steinn Sigurdsson Subject: Goldin's future Newsgroups: sci.space,talk.politics.space In article <1jk1jmINN5vh@mirror.digex.com> prb@access.digex.com (Pat) writes: >In article hagen@owlnet.rice.edu (Jeffrey David Hagen) writes: >>Besides, catch a clue about JPL. It is widely considered to be the single most >>bloated, pig-headed, and inefficient part of NASA among industry folks I have ... In fact, the big push on now is to design probes that bypass NASA infrastructure. NO TDRSS, No SHuttle, NO JPL. direct comms back to the PI's. Does that mean a lot of Universities can look forward to 70m class radiotelescopes on their campuses or are they going to stick very large high power antennas on future probes that go beyond Earth orbit. (I'll grant you easy 9600 baud cellular links to Earth orbit probes via Iridium or other system of your choice!). Just think, the grad students could watch HBO most of the night and then retarget for a high speed download from the Pluto orbiter during the comedy hour... | Steinn Sigurdsson |I saw two shooting stars last night | | Lick Observatory |I wished on them but they were only satellites | | steinly@lick.ucsc.edu |Is it wrong to wish on space hardware? | | "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 | ------------------------------ Date: Wed, 20 Jan 1993 21:40:30 GMT From: shanleyl@ducvax.auburn.edu Subject: Great stuff at NASA and D. WINGO is "why we now" Newsgroups: sci.space In article <1993Jan7.130053.1@fnalo.fnal.gov>, higgins@fnalo.fnal.gov (Bill Higgins-- Beam Jockey) writes: > In article <72528@cup.portal.com>, BrianT@cup.portal.com (Brian Stuart Thorn) writes: > [responding to Allen Sherzer's question:] >>>This is not the case. There is lots of great stuff going on at NASA. I >>>criticize the unproductive things NASA does so that we can have more of >>>the good stuff. Why does that bother you so much? >> >> Because very seldom does anyone ever mention the great stuff >> going on at NASA. > > Emphatically *not* true. That's why God made Dennis Wingo. THAT IS HISTERICAL!!! not that I am disagreeing with you but this^ was a very funny quip. Curiosity? How many people got it? I know Dennis Wingo (I am from Huntsville) but is he known everywhere? Hopefull not like "Dr." Wayne Matson. Oh well, couldn't resist this post...thanks for the chance to chortle. Paul Shanley > > Bill Higgins | Favorite carol around Higgins house: > Fermi National Accelerator Laboratory| Glooooooooooooooria > Internet: HIGGINS@FNAL.FNAL.GOV | In excelsis Deo > Bitnet: HIGGINS@FNAL.BITNET | Deo > SPAN/Hepnet: 43011::HIGGINS | Daylight come and me wanna go home ------------------------------ Date: 20 Jan 93 18:59:28 GMT From: fred j mccall 575-3539 Subject: Let's be more specific (was: Stupid Shut Cost arguements) Newsgroups: sci.space In article <1jc78dINNafi@mirror.digex.com> prb@access.digex.com (Pat) writes: >In article <1993Jan12.171525.7437@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >> >>are a preferred solution. Honeycomb composite structures are another good >>solution, but remain very expensive to fabricate. >> > > >Too the best of my understanding, the chinese use Bamboo heat shields >on their rocket capsules. The bamboo carbonizes, and becomes an almost >perfect insulator. A friend of mine watched a thermite lance get halted >by a piece of plywood. the carbon just sucked up the heat. I believe that what the Chinese are reported to be using is oak, not bamboo. they are also reported to produce a lot of their space hardware in a refrigerator factory, or soemthing like that. So much for Western requirements for Level 100 cleanrooms. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 20 Jan 93 23:29:31 GMT From: Del Cotter Subject: Lunar Rotation (was: Earth's rotation rate...) Newsgroups: sci.space In article "UTADNX::UTDSSA::GREER"@utspan.span.nasa.gov writes: >The moon does spin. Its rotational period is equal to its orbital period >about the Earth, so it always presents the same face to the Earth. This >happened because the distribution of the Moon's mass is not perfectly >spherical; it's a little lumpy. Originally, the Moon was spinning more >quickly than today, but over time, tidal forces working on the lumps in the >Moon slowed it down until the lump with the greatest angular moment became >"locked" into place, so that it always points toward the Earth. The >technical term for this is Gravity Gradient Stabilization. >Dale M. Greer You're right that the lumps determine *which* side of the Moon finally wound up facing us, but it would have slowed down even if it had been a homogeneous fluid mass. The tidal forces deformed the spinning satellite, so that it became an ellipsoid. The satellite swept round, deforming all the while, so that kinetic energy of rotation was dissipated as heat. Incidentally, the angular momentum of rotation was conserved by increasing the angular momentum of revolution (ie. the Earth-Moon distance). The same story can be told a completely different way, using torque on the lagging bulge of the ellipsoid, with no mention of energy. The two descriptions are equivalent, with friction/viscosity the key factor in both. A body made of an *inviscid* fluid would keep spinning forever. BTW, I heard that the Moon is actually *bistable*. Aren't we lucky we got the pretty face? -- ',' ' ',',' | | ',' ' ',',' ', ,',' | Del Cotter mt90dac@brunel.ac.uk | ', ,',' ',' | | ',' ------------------------------ Date: 20 Jan 93 17:49:34 GMT From: Pat Subject: Shuttle safety margins Newsgroups: sci.space In article roberts@cmr.ncsl.nist.gov (John Roberts) writes: > >This is in part a reply to a comment by Pat several weeks ago. Pat was >concerned by mechanical safety margins, and felt that the Shuttle operates >within 5% of destruction for its major mechanical and structural systems. >It's difficult to find anything authoritative on this subject, but there >was mention of one safety factor in the STS-54 post-flight press conference >Wednesday morning. > John Please be very careful of what NASA pulicizes as to their expected margins versus real margins. >It turns out that with the measured wind patterns, if one of the SSMEs had >failed (it didn't) right when the Shuttle was passing Mach 1.55, three of >the struts in the structure would have had a safety factor of 1.36 (36%), >while the target safety factor under those conditions is a minimum of >1.4 (40%). Analysis of the situation and of the particular orbiter indicated >that this safety factor was acceptable, so permission was granted to proceed >with the launch. > NOTE: The phrase measuered wind patterns. In higher strength winds, the vehicle would have lower margins. Post challenger, NASA tightened up the Launch criteria giving a larger margin, not improving the design by 35%. >It should be noted that under normal flight conditions (all three engines >working, which was the case) the safety factor would be greater. > Under normal flight conditions you dont launch in freezing weather. >One of the questions during the press conference was "what if something >additional had happened, and the stress was increased another 36%, so that >zero safety margin was passed?". The spokesman (Brewster Shaw, Deputy >Director of the Space Shuttle Program) replied that the safety margin >stated is not to the point of destruction - you'd get local yielding, >and the load would be redistributed to the surrounding members. (Of course, >orbiter repairs would be needed afterward.) > Local yielding maybe. I'd be worried by such a blithe answer. If local yielding is 1", how much gap does that entail at the ET/ORbiter Feed flange? How much fuel spill will now be observed from this flange? If local yielding increases a moment of torque, will that overstress another member? The mechanical complexity of the Shuttle system is very high, and i doubt NASA still knows it's exact behavior. JOHN my problem with the shuttle is that they used Military safety amrgins. Now when one flys a 747, one does not usually put the vehicle past 1.25 G. The vehicle is rated for 4 Gs. The failure limit is around 6 Gs. 99% of the time you will be below 1.25 Gs. an emergency manuever may require you to pull 4 Gs, everytthing is sized for this. if something unusual occurs you can exceed the limit. Hence 747's have ridden out hurricanes and supersonic dives. Now an F-15 is rated for 9 Gs. THe pilots will routinely pull 9 Gs. but at 10 Gs, structural damage is assumed and the vehicle is overhauled. Now F-15 pilots will pull these high G forces in Training, in operations, in Combat and in emergencies. Which is the Safer airplane? That is engineering judgement. Now the 747 is less likely to break up in an emergency, but on the other hand the 747 is pate to a IR Missile. Just because NASA has now gone and said, we wont launch in heavy weather, doesn't mean that the vehicle may still find itself in extreme conditions. Probably in the post challenger re-design, the struts were improved, having been criticized as weak points, but there are still numerous weak points. Engineering judgement is a funny one. There was a bridge down south, that was hit by a speeding camaro. The bridge collapsed and the state sued the driver. He argued, that a bridge should expect car accidents. THe state won on a negligence issue. but nevertheless, the original point is correct. Certain things must expect certain conditions. Now i dont expect a bridge to withstand the North AMerican Fat ladies precision Hop SCotch squad :-) but i do expect it to withstand 3 cement trucks in close order. Same thing with aircraft. i dont expect nuclear detonations, but i do expect the occasional hurricane. in short, i think NASA has underestimated the expected envelope of shuttle performance areas. Do i have many facts to back it up. not really, just gut feel and the occasional article. pat ------------------------------ Date: 20 Jan 93 22:04:20 GMT From: shanleyl@ducvax.auburn.edu Subject: Territorial conquest? Pishaw!! Newsgroups: sci.space In article <1993Jan19.175517.12514@sunova.ssc.gov>, faught@berserk.ssc.gov (Ed Faught) writes: > In article 18084TM@msu.edu (Tom) writes: >> >>>>>The urge to colonize the universe seems to come from an urge for >>>>>territorial conquest that has been with us for a long time. It is >>>>>interesting how old themes are constantly repeated in the present. >> > IMHO, territorial conquest was the politcal reason used to obtain funding. Yes, much like the authors employers and supporting politicians conquest for large chunks of land in Texas to bury huge tubes to accelerate small things to very fast rates in order to see what happens. Nothing wrong with the premise, learn to learn (plus spin-offs) but cost to learn might have been a worthy consideration. :] Also, the urge to colonize the universe is doubtfully conquestial (word?) in impetus. If it is, it hasn't worked. Seventeen Billion dollars ain't much in the scheme of theings, especially when a small percentage of it is actually for exploring this solar system much less the universe. Just a thought or two, no flame intended. Paul S. Shanley Auburn University pshanley@humsci.auburn.edu or shanleyl@ducvax.auburn.edu ad astra per MYLANTA "Remember, wherever you go, there you are..." ly (word?) l > -- > Ed Faught WA9WDM faught@berserk.ssc.gov > Superconducting Super Collider Laboratory ------------------------------ End of Space Digest Volume 16 : Issue 068 ------------------------------