Date: Fri, 12 Feb 93 18:21:16 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #161 To: Space Digest Readers Precedence: bulk Space Digest Fri, 12 Feb 93 Volume 16 : Issue 161 Today's Topics: Book Computers/AI in Shuttle-SSF hardware on the moon (2 msgs) Honorary Names (was: Today in 1986-Remember the Challenger) HST repair mission Ideal fuel for 'anti-matter' engine Insurance/Liability slush Fun/Dividend kerosene/peroxide SSTO Launching in a Winter Wonderland (was Re: Polar Orbit) (2 msgs) NASA Space Plane New russian solar sail+ Orbital Mechanics--Careers? Payload Hit For Polar Orbit Polar Orbit (2 msgs) Pt 1/2: FREE-ENERGY TECHNOLOGY For Spacecraft Russian Solar Sail experiments ends Sabatier Reactors. Space Station Freedom Fighters Using Off the shelf/incase them! 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: 9 Feb 93 06:23:52 GMT From: nsmca@acad3.alaska.edu Subject: Book Computers/AI in Shuttle-SSF Newsgroups: sci.space That is an idea.. Design the parts of the SSF as cargo spaces.. BAsically have the parts of the new space station as parts of the rocket to refuel other projects.. once the feul tank is in orbit and empty then use it as part of SSF!! Other idea if there is a sattellite that is currently in orbit and is about to die, maybe try to send it up to an orbit where SSF can retrieve it and use its parts and such.. One way to learn about space metallurgy and such. I had an idea that is in the future.. Maybe give astronauts a book computer, have an internal modem where it sends info to the main shuttle/Station computer so that all info that the astronaut wants or can give is put into the computer..Make the book/hand held a writable one where the astronauts can take notes. It might have to be able to handle space walks(?).. Make the Shuttle Computer a AI or a node for a earth bound AI.. Michael Adams Alias: Morgoth/Ghost Wheel nsmca@acad2.alaska.edu ------------------------------ Date: Tue, 9 Feb 1993 01:28:57 GMT From: Bill Goffe Subject: hardware on the moon Newsgroups: sci.space henry@zoo.toronto.edu (Henry Spencer) writes in response to an earlier question: >The later lunar modules were deliberately crashed on the lunar surface >for the benefit of the lunar-surface seismometer network. One or two >of the early ones weren't; I forget whether they were just abandoned >in lunar orbit (from which they almost certainly would have crashed >by now) [further material deleted] Why would they have crashed? With no atmosphere, wouldn't the orbit have been stable? Further, I'd think any orbit would be close to the moon, so it'd be relatively free of perturbations from the earth or sun. Not a big point, just curious what I might be missing. Bill Goffe bgoffe@seq.uncwil.edu ------------------------------ Date: Tue, 9 Feb 1993 02:43:50 GMT From: Dave Michelson Subject: hardware on the moon Newsgroups: sci.space In article <1993Feb9.012857.2251@seq.uncwil.edu> bgoffe@seq.uncwil.edu (Bill Goffe) writes: > >Why would they have crashed? With no atmosphere, wouldn't the orbit >have been stable? Further, I'd think any orbit would be close to the >moon, so it'd be relatively free of perturbations from the earth or sun. > >Not a big point, just curious what I might be missing. The mascons which lie underneath the lunar maria perturb low altitude orbits rather badly. After a number of years, the probability that the perturbed orbit will intersect the lunar surface is apparently rather high. --- Dave Michelson University of British Columbia davem@ee.ubc.ca Antenna Laboratory ------------------------------ Date: Tue, 9 Feb 1993 01:33:56 GMT From: Mary Shafer Subject: Honorary Names (was: Today in 1986-Remember the Challenger) Newsgroups: sci.space,sci.space.shuttle They renamed 10th St East, the street they used to tow the Shuttles between Palmdale and Edwards, Challenger Way. There's also a very nice painting of Dick Scobee in the Test Pilot School auditorium and I think it's now the Scobee Auditorium. (Los Angeles County made a park called Apollo Park out by Fox Field and named the three ponds Armstrong, Aldrin, and Collins, but it's a dubious distinction since they're filled with recycled water from the nearby sewage plant.) -- Mary Shafer DoD #0362 KotFR NASA Dryden Flight Research Facility, Edwards, CA shafer@rigel.dfrf.nasa.gov Of course I don't speak for NASA "A MiG at your six is better than no MiG at all." Unknown US fighter pilot ------------------------------ Date: Mon, 8 Feb 1993 23:45:34 GMT From: "Paul A. Scowen" Subject: HST repair mission Newsgroups: sci.space In article , steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes: |> There's a faint rumour that the "return-to-Earth" option |> for the HST mission has been re-opened and that a committee [sic] |> has been set up to look at that option [again]. |> |> Anyone know whatsup? Are there new concerns over the EVA |> schedule or is this out of the blue. This rumour apparently came from the recent Users Committee meeting at Goddard. I heard that Goldin is being pressured by some Space Station types to minimise the EVA role in the repair mission, because they fear a drop in credibility with the Hill if the mission goes awry. The ST people I've spoken too think that if it does come down it almost certainly won't go back up, because that would be an excellent way to massively reduce the MONDA, wouldn't it (re: Goldin's AAS speech)? Anyway, most people in the know seem to think that it's a pretty ludicrous idea and are hoping that sanity will prevail, especially since we've come this far down the repair mission path. -- ------------------------------------------------------------------------------- Paul A. Scowen INTERNET: scowen@wfpc3.la.asu.edu Department of Physics & Astronomy uk1@spacsun.rice.edu Arizona State University Tel: (602) 965-0938 Box 871504 FAX: (602) 965-7954 Tempe, AZ 85287-1504 ------------------------------------------------------------------------------- ------------------------------ Date: Tue, 9 Feb 1993 06:43:35 GMT From: Adrian Hassall Lewis Subject: Ideal fuel for 'anti-matter' engine Newsgroups: sci.space mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: >The subject pretty much says it all. If you had close to unlimited >energy for input to the fuel (say from anti-matter reactions) as you >exhausted it, what would be the best fuel to carry from a performance >standpoint? Would you go for something relatively dense like mercury >and superheat it to a plasma, do something like a buckyball >massdriver, or still go for the light-weight atoms like hydrogen for >maximum exhaust velocity? >-- >"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. This doesn't really answer your question. But you may like to look up the following reference - Electrostatic propulsion using C60 molecules S. D. Leifer, D. Rapp, and W. A. Saunders Journal of Propulsion and Power Vol.8, no.6, Nov-Dec 1992, pp1297-1300. ajax ------------------------------ Date: 9 Feb 93 06:47:33 GMT From: nsmca@acad3.alaska.edu Subject: Insurance/Liability slush Fun/Dividend Newsgroups: sci.space In article , ewright@convex.com (Edward V. Wright) writes: > In <1993Feb5.141720.1@acad3.alaska.edu> nsmca@acad3.alaska.edu writes: > >>Maybe the US can start their own >>Lloyds for space related projects.. >>Use the money left over in the "Insurance" >>fund for the next year.. > > Uh, what money left over? The record of the space-insurance > industry is that they pay out more money than they take in. I mean take a few million and put it in a fund, use most for "insurance" the rest for investments and take the money left over each year (yes if there is any) and use it to fund next years Insurance.. Kind of liek the permenant fund here in Alaska.. Maybe also take the inventions that have been made or so some said by NASA and the shuttle and sell them for royalties,. Take the royalties and invent them and use part of the interest/dividends for "insurance"... Maybe make NASA into a semi-money making project.. It can still be a government agency, but it is tiem the US sold the inventions made at government labs and such.. They the labs are government property and such, but that does not mean they can't support themselves andf save the tax payers money.. Why must the big corps make big money on products given them for "free" and then sell them to us the population for high prices and run the medical cost up with them.. Michael Adams Alias: Morgoth/Ghost Wheel nsmca@acad2.alaska.edu ------------------------------ Date: 8 Feb 93 19:57:24 GMT From: Craig Meyer <01crmeyer@leo.bsuvc.bsu.edu> Subject: kerosene/peroxide SSTO Newsgroups: sci.space > Also of note were the peroxide monopropellant rocket engines used in the > NF-104 rocket-boosted aircraft flown by NASA and the USAF, which worked > quite well and were serviced and fuelled by ordinary USAF technicians. I, the space-dunce, would like to know how H2O2 could serve as a monopropellant when the decomposition of H2O2 is an endothermic reaction (takes up energy). Could someone please explain the chemical reaction? > As mentioned elsewhere, Mitch went so far as to sketch out a design for > a pressure-fed reusable SSTO, although Bruce Dunn has cast some serious > doubts on Mitch's weight estimates for pressurization gas. The space-dunce's instincts say that eliminating a mechanical fuel-delivery system would greatly simplify a launch vehicle. Thicker tanks SEEM to be worth it, but I don't know the numbers. -- Craig Meyer 01CRMEYER@LEO.BSUVC.BSU.EDU Indiana Academy for Science, Mathematics, and Humaities. Muncie, IN 47306 317-285-7433 Opinions expressed are mine alone, and not necessarily shared by the Indiana Academy. ------------------------------ Date: Mon, 8 Feb 1993 23:47:59 GMT From: kjenks@gothamcity.jsc.nasa.gov Subject: Launching in a Winter Wonderland (was Re: Polar Orbit) Newsgroups: sci.space nsmca@acad3.alaska.edu wrote: : In article , gnb@baby.bby.com.au (Gregory N. Bond) writes: : > And did you hear that researchers in Fairbanks, Alaska have developed : > room-temperature superconductors? : I have not heard that.. I will check it out.. Unles this is a hoax? It's a joke, son. Think about it. Of course, we don't get winter here in Houston. It just rains a little more. My wife has Renault's Syndrome [sp?], a problem with blood flow to the hands which gives her perpetually cold fingers. Her doctor back in Illinois told her to move someplace warm. It's a darned good thing that most of the space program is located where it's warm -- Texas, California, Florida, Alabama (not in any particular order). It's be hell on her to live in Alaska. -- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office kjenks@gothamcity.jsc.nasa.gov (713) 483-4368 "We choose to go to the moon not because it is easy, but because it is fun." -- John F. Kennedy, as [mis]quoted by Scott Brigham, scotbri@rosemount.com, in alt.folklore.urban ------------------------------ Date: Tue, 9 Feb 1993 01:04:33 GMT From: Leigh Palmer Subject: Launching in a Winter Wonderland (was Re: Polar Orbit) Newsgroups: sci.space In article <1993Feb8.234759.7988@aio.jsc.nasa.gov> , kjenks@gothamcity.jsc.nasa.gov writes: >My wife has Renault's Syndrome [sp?], a problem with blood flow to the >hands which gives her perpetually cold fingers. I think that's Reynaud's Syndrome (but I'm not sure, either); it is not uncommon. I've got it, too. Renault's Syndrome is indicated when an otherwise sane person suddenly buys a French car. Leigh ------------------------------ Date: 9 Feb 93 06:48:00 GMT From: Avatar Subject: NASA Space Plane Newsgroups: sci.space Dear friends, What is the present status of the NASA Space Plane? I am aware that the NASA Space Plane is designed to use some sort of scramjet/ramjet (?) propulsion system in the atmosphere, but what sort of propulsion system is it designed to use in space? . .'|`. ___________________________________.'-{*}-`.____________________________________ Zerxes M. Bhagalia '----|----` INT: v064lnev@ubvms.cc.buffalo.edu State University of New York .---------------. bhaga-z@acsu.buffalo.edu at Buffalo .' `. News Director, WFFT 104.9 FM Political Science .' `. Justice, SA Judiciary (SWJ) Computer Science .'________MDCCLXXVI________`. Computer Consultant (UCS) ---------------------N O V U S O R D O S E C L O R U M---------------------- ------------------------------ Date: 9 Feb 93 06:09:33 GMT From: nsmca@acad3.alaska.edu Subject: New russian solar sail+ Newsgroups: sci.space In article <729180028.AA00000@blkcat.UUCP>, Keith.Stein@f118.n109.z1.fidonet.org (Keith Stein) writes: > The separation of the sail and PROGRESS was a scheduled event. They both > will reenter and burnup very soon I heard. > Any idea when they will burn up and where should we watch?(I know Im out of the pale, but others might liek to know)... == Michael Adams alias Ghost Wheel/Morgoth NSMCA@acad2.alaska.edu ------------------------------ Date: Mon, 1 Feb 1993 22:51:33 GMT From: " John O. Bell II " Subject: Orbital Mechanics--Careers? Newsgroups: sci.aeronautics,sci.research.careers,sci.space,soc.college.grad >In <1993Jan28.005309.674@chpc.utexas.edu> byab314@chpc.utexas.edu (Srinivas Bettadpur) writes: > >> * I know of UT-Austin, MIT, Stanford, UC-Boulder, VPISU, U. Mich-Ann >>Arbor, U. Ill.-UC, Purdue, Auburn U. as offering any significant ^^^^^^^^^^ >>graduate programs in CM in the US. If you ever get the chance, take a very close look at the Aero Engineering grad program at the U of Illinois... especially for concentration in the field of Orbital/Celestial Mechanics. The university is getting gobs of money poured into it, the dean (Prof. Solomon) is on a mission to make it the top AAE grad school in the country, and if you're lucky and say your prayers :-) you'll get to work with either Prof. J. E. Prussing or Prof. B. A. Conway, both highly respected contributors to the field and quite pleasurable to work with. I know, I know, my check's in the mail... :-) (but believe me, they are _excellent_ teachers at an excellent school). John Bell Applied Computing Devices, Inc. jbii@hdfs1.acd.com P.S. Yes, I graduated from U of I with a degree in Aeronautical Engineering (how did you _ever_ guess :-) ). ------------------------------ Date: Tue, 09 Feb 1993 03:00:26 GMT From: Dave Rickel Subject: Payload Hit For Polar Orbit Newsgroups: sci.space In article , "UTADNX::UTDSSA::GREER"@utspan.span.nasa.gov writes: |> We know that kinetic energy varies with the square of the velocity. Orbital |> velocity at 300 km altitude is about 7700 meters/second, while the velocity of |> the surface of the Earth at the equator is about 460 m/s... OK, what is important is delta-V. Using your numbers: Equator launch - equatorial orbit 7240 m/s Equator launch - retrograde equ. orbit 8160 m/s Equator launch - polar orbit 7714 m/s Pole launch - polar orbit 7700 m/s Pretty clearly, the differences in velocity needed for polar orbit from the equator or polar orbit from a pole are pretty insignificant. Anyway, plucking numbers out of the air, let's assume that you always need an additional 1.5 km/sec to make orbit (atmospheric effects), and that your effective exhaust velocity is 4.4 km/sec. So the table now goes Launch delta V effective required type (km/sec) delta V mass ratio (km/sec) E - E 7.24 8.74 7.29 E - RE 8.16 9.56 8.78 E - P 7.714 9.214 8.12 P - P 7.7 9.2 8.09 Using these numbers, the penalty for equatorial launch into polar orbit vs polar launch into polar orbit is on the order of 0.4%. david rickel drickel@sjc.mentorg.com ------------------------------ Date: 9 Feb 93 02:34:23 GMT From: "David M. Faubert" Subject: Polar Orbit Newsgroups: sci.space >"In projecting a satellite into Earth orbit, the launch vehicle is invariably >tilted after liftoff in an easterly direction. Launching to the east is done >to take advantage of the Earth's eastward surface velocity. This rotational >surface velocity is about 1500 feet (450 metres) per second at the equator and >1370 feet (400 metres) per second at the latitude of Cape Kennedy. It would be >perfectly possible to launch a satellite on a westerly orbit, but an additional >2000 feet (600 metres) per second would be required for an orbit of the same >altitude compared with an easterly one. > If the satellite is launched in a northerly or southerly direction, a polar >orbit is obtained. The easterly surface velocity launch advantage is lost" >It's just a guess, but I think it would be more advantageous to look for a high >mountain from which to launch rather than a northerly latitude. That way you'd >have less of that thick air to punch through. >Chris Jones clj@ksr.com OK, I'm not a space scientist or an academic but an engineer with a reasonable background in physics. Agreeing with the Brittanica excerpt, I ask you: Since polar orbits have no "easterly" or "westerly" velocity, wouldn't it be most advantageous to launch near one of the poles? If you launch an object from the equator, say, you would have to lose all of that "easterly" velocity in order to put the thing in a polar orbit at all. Ideally, launching from one of the poles, all of your delta-v would go into the orbit and not into compensating for the rotation of the earth. I was recently at the ESA facilty in Kiruna, Sweden at 68 degrees north latitude. One of the selling points of this sight for future development is the relative ease with which satellites can be launched into polar orbits. Dave Faubert . ------------------------------ Date: Tue, 9 Feb 1993 05:10:20 GMT From: Dave Michelson Subject: Polar Orbit Newsgroups: sci.space In article <4015@mdavcr.mda.ca> faubert@mdavcr.mda.ca (David M. Faubert) writes: > >OK, I'm not a space scientist or an academic but an engineer with a reasonable >background in physics. Agreeing with the Brittanica excerpt, I ask you: Since >polar orbits have no "easterly" or "westerly" velocity, wouldn't it be most >advantageous to launch near one of the poles? If you launch an object from the >equator, say, you would have to lose all of that "easterly" velocity in order >to put the thing in a polar orbit at all. Ideally, launching from one of the >poles, all of your delta-v would go into the orbit and not into compensating >for the rotation of the earth. Try working out the math. The penalty for launching from the equator appears to be fairly small because the velocity that you're trying to kill is both fairly small and at right angles to the desired velocity. Unless I'm missing something. >I was recently at the ESA facilty in Kiruna, Sweden at 68 degrees north >latitude. One of the selling points of this sight for future development >is the relative ease with which satellites can be launched into polar orbits. It certainly appears to be a commonly held belief... --- Dave Michelson University of British Columbia davem@ee.ubc.ca Antenna Laboratory ------------------------------ Date: Sat, 06 Feb 1993 13:17:01 From: Bogdan Eremia Subject: Pt 1/2: FREE-ENERGY TECHNOLOGY For Spacecraft Newsgroups: sci.space mm> One other energy source should be mentioned mm>here, mm> despite the fact that it does not fit the mm>definition of Free mm> Energy. A Bulgarian-born American Physicist named mm>Joseph mm> Maglich has invented and partially developed an atomic FUSION mm> reactor which he calls 'Migma', which uses NON-radioactive mm> deuterium as a fuel [available in nearly UNLIMITED quantities mm> from sea water], does NOT produce radioactive waste, can be mm> converted DIRECTLY into electricity (with-OUT energy-wasting mm> steam turbines), and can be constructed small enough to power mm> a house or large enough to power a city. And UNLIKE the mm> "Tokamaks" and laser fusion MONSTROSITIES that we read about, mm> Migma WORKS, already producing at least three watts of power mm> for every watt put in. ["New Times" (U.S. Just one question....why aren't we using these already? * Origin: Empire BBS +61(3)592-5662 (3 lines) (3:635/550) ------------------------------ Date: Tue, 9 Feb 1993 04:24:29 GMT From: Glenn Chapman Subject: Russian Solar Sail experiments ends Newsgroups: sci.space The Russian solar sail Znamya experiment ended yesterday (Sunday, Feb. 7th) when the sail entered the atmosphere. Current reports indicate that initial results went well after it was deployed from the Progress TM-15 cargo craft at the Mir space station about 4 am UTC (11 pm PST) Feb. 4th. The solar sail illumined several areas in Europe, especially in Toulouse France. Apparently in that southern French city, near the Spanish boarder, the streets were noticeably brighter during the pass as seen by several town people. Shortly after it crossed the day/night terminator in Europe the solar sail was released from the Progress. Observations here in Vancouver suggested that it fell about 95 Km (60 mi) to about 300 km altitude in just about 30 hours, by Friday (Feb. 5th) morning. Since such orbital decays would increase rapidly so it would seem that by Feb. 6th it would have been down to a 200 km orbit, and renter shortly there after on Feb. 7th as reported. This is not unreasonable for a 20 metre (85 ft) diameter very light sail. Some reports indicate that the Znamya was set free after the rotation which was to stabilized its shape caused problems with the Progress' guidance. However, note that the original experimental plan called for only about 3 days of flight, consistent with this same time frame. Until more reports come out it is not possible to tell which was the reason for the release. Dr. Leigh Palmer here observed the Mir space station on Feb. 7th, but the Progress was no longer near it, so that has probably deorbited by now as well. That would be consistent with standard operations. (Radio Moscow, BBC, CBC) Certainly this ranks as one of the more noticed Russian/CIS space experiments in recent years. Yours truly Glenn Chapman Simon Fraser U. glennc@cs.sfu.ca ------------------------------ Date: Mon, 8 Feb 93 17:59:21 PST From: Brian Stuart Thorn Subject: Sabatier Reactors. Newsgroups: sci.space >And the Soviets have had an unmanned resupply craft, launched on a >cheap, Atlas-class launcher, available for such refullings. As >far as I know, NASA has no plans to develop such a craft, and as >a cargo/fuel transport the Shuttle isn't exactly cost-effective... >By the way, how do they plan to get around the no-liquid-fuel-payload >requirement imposed on the Shuttle after the Challenger accident? > > Frank Crary There is no such requirement. What did happen was that Centaur was banned from Space Shuttle operations, but this was a case of Centaur being too heavy and carrying too much fuel to dump in an emergency. Liquid fuels are still okay, but the U.S. has no other liquid-fuel upper stages (Agena being dead and gone.) Most satellite carried aloft by the Shuttle have liquid fueled propulsion systems, such as TDRS, Galileo, Magellan, UARS, and EURECA. Also, Shuttle EDO pallets carry a significant amount of cyrogenic fuels in the payload bay. -Brian ------------------------------------------------------------------------- Brian S. Thorn "If ignorance is bliss, BrianT@cup.portal.com this must be heaven." -Diane Chambers, "Cheers" ------------------------------------------------------------------------- ------------------------------ Date: Tue, 9 Feb 1993 01:56:00 GMT From: gawne@stsci.edu Subject: Space Station Freedom Fighters Newsgroups: sci.space In article <1993Feb8.033933.1868@aio.jsc.nasa.gov>, munoz@sweetpea.jsc.nasa.gov (tomas o munoz 283-4072) writes: > This message is posted as a favor to the Space Station Freedom Fighters. Who will no doubt become known as Space Station Terrorists in unsympathetic venues... > Engineers think equations are an approximation of reality. > Physicists think reality is an approximation of the equations. > Mathematicians never make the connection. But only Physicists can assume a bridge and go home. -Bill Gawne, Space Telescope Science Institute "Forgive him, he is a barbarian, who thinks the customs of his tribe are the laws of the universe." - G. J. Caesar ------------------------------ Date: 9 Feb 93 06:07:33 GMT From: nsmca@acad3.alaska.edu Subject: Using Off the shelf/incase them! Newsgroups: sci.space Why can't off the shelf items be used in space, you might have to incase them in soemthing that meets the specs (namely outgassing and such), and have some form of interface (remember boy in the bottle). So that you can use off the shelf equipment, you just put them in a position where there dangers are neutralized.. == Michael Adams alias Ghost Wheel/Morgoth NSMCA@acad2.alaska.edu ------------------------------ Received: from crabapple.srv.cs.cmu.edu by VACATION.VENARI.CS.CMU.EDU id aa14013; 9 Feb 93 0:46:56 EST To: bb-sci-space@CRABAPPLE.SRV.CS.CMU.EDU Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!ogicse!uwm.edu!cs.utexas.edu!torn!utzoo!henry From: Henry Spencer Newsgroups: sci.space Subject: Re: hardware on the moon Message-Id: Date: 9 Feb 93 01:59:30 GMT Article-I.D.: zoo.C25s78.LD4 References: <6752@rosie.NeXT.COM> <1993Feb9.012857.2251@seq.uncwil.edu> Organization: U of Toronto Zoology Lines: 18 Sender: news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU In article <1993Feb9.012857.2251@seq.uncwil.edu> bgoffe@seq.uncwil.edu (Bill Goffe) writes: >>... early ones weren't; I forget whether they were just abandoned >>in lunar orbit (from which they almost certainly would have crashed >>by now) [further material deleted] > >Why would they have crashed? With no atmosphere, wouldn't the orbit >have been stable? Further, I'd think any orbit would be close to the >moon, so it'd be relatively free of perturbations from the earth or sun. But not from the Moon itself. The Moon's gravitational field is very lumpy, thanks to the mascons (heavy spots in its crust). It is not particularly well mapped, but so far as we know there is no such thing as a stable lunar orbit in the long term. They all get perturbed enough to intersect the surface eventually. Designs for lunar orbiters have to include quite substantial amounts of orbit-correction fuel. -- C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology effect since OS/360. | henry@zoo.toronto.edu utzoo!henry ------------------------------ End of Space Digest Volume 16 : Issue 161 ------------------------------