Date: Fri, 30 Oct 92 05:00:06 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #357 To: Space Digest Readers Precedence: bulk Space Digest Fri, 30 Oct 92 Volume 15 : Issue 357 Today's Topics: "Earth gains a retinue of mini-asteroids" (2 msgs) A career in Aerospace? Apollo - Southern Style with a side of grits Comet Collision Mini-asteroids part two. orbit code needed Post WARC Putting volatiles on the moon (2 msgs) QUESTIONS: Apollo, Earth, Moon Re:Swift-Tuttle Comet a threat to earth? Scenario of comet hitting Earth Solar Sails (3 msgs) Swift-Tuttle Comet a threat to earth? UFO EVIDENCE VS. Carl Sagan What does the "P/" mean in P/Swift-Tuttle? (3 msgs) 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: 29 Oct 92 17:07:29 GMT From: Paul Dietz Subject: "Earth Gains a Retinue of Mini-Asteroids" Newsgroups: sci.astro,sci.space Science (10/16/92, page 403), reports that Gehrels and colleagues in the Spacewatch program have detected 8 very near earth asteroids over the last two years with sizes from 5 to 100 meters. This implies that at any time, there are as many as 50 mini-asteroids passing between the Earth and Moon every day. This figure is some 100 times larger than had been inferred from observations of the number of larger bodies. Since the Tunguska event is thought to have been due to a 40 meter body, and such events were calculated to occur once every 2 to 3 centuries, something is screwy here. The orbits of the bodies are unexpectedly similar to Earth's. Two have orbits more like earth's than any known body; one was that asteroid that was mistaken for a spent rocket body. These couldn't be Frank's minicomets, could they? His putative objects are supposedly in prograde, earth-like orbits, to reduce the impact velocity enough to avoid observational constraints. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Thu, 29 Oct 92 13:11:40 -0600 From: pgf@srl05.cacs.usl.edu (Phil G. Fraering) Subject: "Earth gains a retinue of mini-asteroids" >The orbits of the bodies are unexpectedly similar to Earth's. >Two have orbits more like earth's than any known body; one was that >asteroid that was mistaken for a spent rocket body. >These couldn't be Frank's minicomets, could they? His putative >objects are supposedly in prograde, earth-like orbits, to reduce the >impact velocity enough to avoid observational constraints. I think Frank's minicomets, although I don't have the ref. with me, were supposed to be a little faster than this, but still prograde. And a lot dimmer. I'd bet Frank will claim that these bodies represent the "larger" members of his mini-comet population, but I don't know. I do know that Dr. Louis Frank has an e-mail address. Proof is left as an exercise for your local Gopher server. And I'm sure he's better qualified to tell you his opinions than I am. I'm not sure I agree with him, but his book was pretty good... -- Phil Fraering pgf@srl0x.cacs.usl.edu where the x is a number from 1-5. Phone: 318/365-5418 SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560 --------------------- Disclaimer: Some reasonably forseeable events may exceed this message's capability to protect from severe injury, death, widespread disaster, astronomically significant volumes of space approaching a state of markedly increaced entropy, or taxes. The world will end tomorrow. NASA scientists note that this was the way the system was designed to operate. - From the Nov. Focus in Sky and Telescope, on a hypothetical NASA press release on something hitting the Earth... ------------------------------ Date: Thu, 29 Oct 1992 10:59:33 -0500 From: jaj1@cornell.edu (John Judge) Subject: A career in Aerospace? I am a college freshman considering a career in aerospace. What are the chances that the job market will improve by the time I graduate? John Judge ------------------------------ Date: 29 Oct 92 18:55:03 GMT From: Spiros Triantafyllopoulos Subject: Apollo - Southern Style with a side of grits Newsgroups: sci.space In article <1992Oct28.200115.11690@iti.org> aws@iti.org (Allen W. Sherzer) writes: >In article Wales.Larrison@ofa123.fidonet.org writes: >>Bill Higgins proclaims: >>>>>It worked, too. Southerners put us on the Moon... > >>>> At Lewis there is a persistant rumor that they could not have >>>>done it without some help from North of the Mason-Dixon line... > >> And a few California drawls too, dude.... How about a few Milwakee-ans? Delco (AC Electronics at the time) built computer hardware for the Apollo program. The automotive electronics program started with many of the Apollo hardware folks from Milwakee. I've seen Apollo project reunions in our internal literature. The moon rover was built by GM, but I believe it was done in dude country (Southern California). Spiros -- Spiros Triantafyllopoulos c23st@kocrsv01.delcoelect.com Software Technology, Delco Electronics striantafyll@kosds1.gm.hac.com GM Hughes Electronics, Kokomo, IN 46904 [A Different Kind of Disclaimer] ------------------------------ Date: 29 Oct 92 15:43:35 GMT From: gawne@stsci.edu Subject: Comet Collision Newsgroups: sci.space In article <1992Oct28.181745.11840@afit.af.mil>, morlan@afit.af.mil (Bruce W. Morlan) writes: > rsb@mcc.com (Richard S. Brice) writes: > >>Would anyone care to comment on how probability plays a role in the >>future interactions of earth and comet P/S-T and how much of the >>script is already written into the clock? > > Sure. The script is nearly totally written. The Heisenberg uncertainty > associated with the objects in question (Earth, comet, Sun, other > planets, etc.) is practically 0 over the time frame in question. On the > other hand, the _uncertainty_ in the measurements leave much room for > surprises. I cannot comment on the measurement errors. Just what does Heisenberg uncertainty have to do with this? We're not talking about a system small enough or fast enough to need any of the tools of Quantum Mechanics. -Bill Gawne, Space Telescope Science Institute ------------------------------ Date: Thu, 29 Oct 92 13:33:32 -0600 From: pgf@srl05.cacs.usl.edu (Phil G. Fraering) Subject: Mini-asteroids part two. >Since the Tunguska event is thought to have been due to a 40 meter >body, and such events were calculated to occur once every 2 to 3 >centuries, something is screwy here. I've done some more thinking about this. Let's fudge the properties of these objects so that they don't conflict with what we've already seen: Specifically, let's make them low density, so they don't hold together well, or last long enough in the atmosphere to cause a big show. Snow would be an ideal candidate. Of course, if they were bare ice, they'd be bright, so let's give them a coating of that gooey stuff that was on the rings of Uranus and Neptune, to make them more reasonably dark. Now they also absorb radar signals. But this sounds too much like _that_ guy's theory, so it can't be right... >The orbits of the bodies are unexpectedly similar to Earth's. >Two have orbits more like earth's than any known body; one was that >asteroid that was mistaken for a spent rocket body. >These couldn't be Frank's minicomets, could they? His putative >objects are supposedly in prograde, earth-like orbits, to reduce the >impact velocity enough to avoid observational constraints. Now that I think about it, Frank has (again going from memory) specified the orbital parameters of these hypothetical bodies pretty closely... These might be the _slower_ members of the population... > Paul F. Dietz > dietz@cs.rochester.edu Disclaimer: I don't know; I'm just guessing. Anyone here read _The Big Splash_? -- Phil Fraering pgf@srl0x.cacs.usl.edu where the x is a number from 1-5. Phone: 318/365-5418 SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560 --------------------- Disclaimer: Some reasonably forseeable events may exceed this message's capability to protect from severe injury, death, widespread disaster, astronomically significant volumes of space approaching a state of markedly increaced entropy, or taxes. The world will end tomorrow. NASA scientists note that this was the way the system was designed to operate. - From the Nov. Focus in Sky and Telescope, on a hypothetical NASA press release on something hitting the Earth... ------------------------------ Date: 29 Oct 92 18:18:46 GMT From: Douglas Strickland Subject: orbit code needed Newsgroups: sci.space Hello: I am in need of an orbit code for satellite altitude approximately at 800 km (period is about 100 minutes, I think). It has to be fairly accurate so I can not use codes written for amateurs. Does anyone know about the availability of such software, public or commercial, perhaps in FORTRAN? Thanks in advance. Mike Shen shen@euler.cpi.com ------------------------------ Date: 28 Oct 92 10:48 PST From: Public Service Telecommunications Consortium Subject: Post WARC Newsgroups: sci.space On the assumption there are people on the conference concerned with telecommunications and space, I would like to solicit some views, especially from European readers. The World Administrative Radio Conference (WARC) provided a variety of allocations for new services. I am especially interested in LEOs, and the set asides for their operation. The U.S. delegation to WARC came home claiming victory; it had obtained what was wanted for Motorola's IRIDIUM and others like it. The European post- WARC view was that the U.S. should not be so sure of itself; one delegate was quoted as saying, "the devil is in the details." The "details," in this case, were the many footnotes and reservations not seen by all when the Final Acts were signed in a frenzy of late night activity. I know it is difficult to make predictions, especially about the future, but I'd be interested in informed views of how things are going to shape up, especially in light of European displeasure with the results the U.S. thinks it obtained. If you'd care to answer via e-mail, many thanks and I'm Bert Cowlan, Public Service Telecommunications Corporation, a nonprofit thinktank. Address . ------------------------------ Date: 29 Oct 92 02:28:51 GMT From: "John A. Weeks III" Subject: Putting volatiles on the moon Newsgroups: sci.space In <1992Oct27.050516.5867@rvgs.vak12ed.edu> abond@rvgs.vak12ed.edu writes: > As a method of steering the comets, a few large nukes could give a comet > enough of a push to do the job. Also a good usefull way of turning swords > into plowshares! I find that it is a wonder that man is so hesitant to use > his most powerful tool for anything except as a weapon. Eeek! I was looking for a smiley at the end of your post, but I didn't find one. While I don't know about using nukes to nudge comets, I have recently heard a few stories about the Soviet Union using nuclear bombs for peaceful purposes. They reportedly dug canals with a-bombs, seriously polluting several rivers in the process. They also used a-bombs as a mining explosive--then sent unprotected workers into the mine only hours after the explosion. Please try to refrain from using nukes for anything other than blowing up people, and I really hope we don't use them for that purpose either. -john- -- ============================================================================== John A. Weeks III (612) 942-6969 john@newave.mn.org Newave Communications, Ltd. ..!uunet!tcnet!newave!john ------------------------------ Date: 29 Oct 92 18:18:33 GMT From: Henry Spencer Subject: Putting volatiles on the moon Newsgroups: sci.space In article <178@newave.newave.mn.org> john@newave.newave.mn.org (John A. Weeks III) writes: >> As a method of steering the comets, a few large nukes could give a comet >> enough of a push to do the job. Also a good usefull way of turning swords >> into plowshares! ... > >... Please try to refrain from using nukes for anything >other than blowing up people, and I really hope we don't use them for >that purpose either. Far more people have been blown up by conventional explosives than by nuclear weapons. Should we therefore refuse, on high moral principles, to use dynamite for construction? This is silly. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 29 Oct 92 17:56:24 GMT From: Henry Spencer Subject: QUESTIONS: Apollo, Earth, Moon Newsgroups: alt.sci.planetary,sci.astro,sci.space In article <1cnihlINN59s@uwm.edu> wlee@csd4.csd.uwm.edu (Wan Ngai Wayne Lee) writes: > ... the astronauts passed through a "dead man's zone" during > which a descent stage failure could not be solved by using > the ascent stage to return to orbit... > a. Did this only apply to the early missions or did the "dead > man's zone" possibility apply to all of the moon shots? All of them. Such zones are also known as "black zones". In the case of the lunar landings, as far as I know there was only one: a descent-stage failure at very low altitude would not leave enough time for staging and ascent-stage ignition before the crash. As far as I know, if they could get the ascent stage lit and if it stayed lit for a while, they always had an abort procedure available (although some required CSM cooperation). > b. If the descent stage would have failed, would the procedure > have been for the astronauts to continue dropping to the > surface or attempt an abort to orbit? Without the descent stage, landing was not possible. The descent stage carried the landing gear. It also had the throttlable engine needed for a soft landing. (Making a rocket engine throttlable is not simple and is done only when necessary; the ascent-stage engine was not throttlable.) Even if you could land with the ascent stage, you wouldn't have the fuel to return thereafter. > During the Apollo missions, was it ever possible for Earth-based > radar to determine where moon-orbiting craft were? It is my > impression that the answer was no... Wrong, in fact very wrong. All the precision navigation was done by Earth-based tracking. However, this tracking did rely heavily on the transponders (which, speaking sloppily, basically amplify the received signal and retransmit it) carried by the spacecraft. "Skin tracking" -- tracking an uncooperative object by its radar reflection -- was not practical for objects of that size at that distance, and still isn't. > Has the prehistoric "flip" of Earth's magnetic field been proven? It's about as well proven as it can be, although the geologists are still arguing about details. > What may cause this in the future? It seems to happen periodically. Just how quickly it happens, and whether it is spontaneous or triggered by something, is unclear. > Does the Moon has its own magnetic field? If I had a compass on > the moon, how would it behave? The Moon's magnetic field is feeble and confused. A compass would not be useful. > In the 1970's, I read that Apollo 12 & 14 ALSEP sensors (ION) picked > up what seemed to be a water vapor emission near Fra Mauro. What > would be an alternative explanation for such readings? Nobody seriously doubts that the Moon still outgasses a little here and there. Whether substantial deposits of volatiles still exist in reachable places is another question. > How respectable is the notion that frozen water may exist on the moon > and how would such a discovery related to moon's origin & history? Very respectable, but it would have to have arrived after the Moon's formation and early volcanic period. There is considerable suspicion that volatiles deposited on the Moon by comet impact may still exist, frozen in polar craters which never get direct sunlight. Suspicions have been strengthened considerably of late because radar mapping has discovered what is probably ice at the poles of Mercury (!). Flying a gamma-ray spectrometer in low lunar polar orbit, which would (among other things) let us survey the entire Moon for near-surface ice, is a very high priority for lunar scientists. > By the way, Arthur C Clarke has put moon water in his 2061 novel. Lunar water, either as fossil ice or water of hydration, has been a staple of science fiction for a long time. It came as a bit of a shock when Apollo samples showed that the Moon was very thoroughly baked early in its history, which means no fossil ice and no water of hydration. Any volatiles on the Moon are more recent arrivals. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 29 Oct 92 18:00:38 GMT From: James Davis Nicoll Subject: Re:Swift-Tuttle Comet a threat to earth? Newsgroups: sci.astro,sci.space I was noodling around with impact energy estimates for S-T, and got a value of about 30 million megatons. *IF* the energy were distributed like a nuke's (Which it wouldn't be, but maybe it's good enough for my purposes), you could expect buildings to be seriously damaged over an area about 4200 km wide, and windows to be shattered over an area 12,000+ km wide. Fires should extend out to the horizon,whatever that is in this case. While fallout would be non-radioactive, there'll be gigatons of the crap blocking sunlight. The crater should be very impressive: ~50 km wide and 25km deep, although I expect it wouldn't stay that way for long. James Nicoll ------------------------------ Date: Thu, 29 Oct 1992 17:03:49 GMT From: hathaway@stsci.edu Subject: Scenario of comet hitting Earth Newsgroups: sci.astro,sci.space In article <92302.164139C09630GK@wuvmd.wustl.edu>, Gary Kronk writes: > [...stuff deleted...] > > WHAT MIGHT HAPPEN IF COMET SWIFT-TUTTLE HIT EARTH > [...stuff deleted...] > Perhaps it is comforting to know that we are aware of the chances > for Swift-Tuttle hitting the Earth in 134 years. Maybe sometime in > the future something could be done to help protect Earth from this > comet, like a couple of space probes carrying nuclear warheads which > could destroy the comet if its recovery in 2125 or 2126 reveals the > threat of collision with Earth still exists. [...stuff deleted...] Just because a nuclear explosion could 'destroy' a comet, does not mean that the material making up the comet would thereby _disappear_ (conservation of matter), nor would the rubble necessarily not continue on the same trajectory as it did before being nuked (conservation of momentum and energy). A pile of debris hitting the earth at 60 km/sec could make a mess just as surely (if not as effectively) as an intact comet. (This is one of the SDI falacies of 'shooting down' ballistic missles. They be coming down no matter what. Like the SCUDs - hitting a missle ain't enough.) What we have to do is ensure the orbit is a safe one - don't matter if it's broken apart, just so it misses. And a small, steady thrust over a long period of time could be just as effective, if not as spectacular, as a last-minute explosion. BTW, other than that minor quibble, the original posting answerd the question well. WHH - still here %-) ------------------------------ Date: 29 Oct 92 15:12:01 GMT From: Brad Whitehurst Subject: Solar Sails Newsgroups: sci.space In article <1992Oct28.235558.1187@ucsu.Colorado.EDU> fcrary@ucsu.Colorado.EDU (Frank Crary) writes: >In article <1992Oct28.202753.10814@murdoch.acc.Virginia.EDU> rbw3q@rayleigh.mech.Virginia.EDU (Brad Whitehurst) writes: >>>Well, so solar sails are just "driven by radiation pressure". I'd heard >>>that (as well as solar wind) before. > >> Well, I don't have any numbers, but don't forget the "solar >>wind" of particles streaming from the sun. I would think it would >>have a significant contribution. > >The particle momentum is less than 1% that of the radiation pressure. >However, there is a idea for using it (Zubrin's Magsail): The particles >are charged, and interact with magnetic fields. In theory, a loop of Interesting. NPR had a bit this AM about the solar sail "regatta" to the moon. I didn't listen closely, but they did speak of using the solar particle wind. Is this an error on their part, or is the particle flux in the earth-moon system stronger somehow? (acceleration in the magnetosphere or some such?) -- Brad Whitehurst | Aerospace Research Lab rbw3q@Virginia.EDU | We like it hot...and fast. ------------------------------ Date: Thu, 29 Oct 1992 17:16:04 GMT From: Frank Crary Subject: Solar Sails Newsgroups: sci.space In article <1992Oct29.151201.8187@murdoch.acc.Virginia.EDU> rbw3q@rayleigh.mech.Virginia.EDU (Brad Whitehurst) writes: >>The particle momentum is less than 1% that of the radiation pressure. > Interesting. NPR had a bit this AM about the solar sail >"regatta" to the moon. I didn't listen closely, but they did speak of >using the solar particle wind. Is this an error on their part, or is >the particle flux in the earth-moon system stronger somehow? An error on their part: The radiation pressure at the Earth is of order P/c = 1.4E3/3E8 = 5E-6 newtons/m^2. The particle pressure is of order Nmv^2 = 9E6*1.6E-27*5E5^2 = 3E-9 newtons/m^2. Frank Crary CU Boulder ------------------------------ Date: 29 Oct 92 17:58:26 GMT From: Henry Spencer Subject: Solar Sails Newsgroups: sci.space In article <1992Oct29.151201.8187@murdoch.acc.Virginia.EDU> rbw3q@rayleigh.mech.Virginia.EDU (Brad Whitehurst) writes: > ... NPR had a bit this AM about the solar sail >"regatta" to the moon. I didn't listen closely, but they did speak of >using the solar particle wind. Is this an error on their part, or is >the particle flux in the earth-moon system stronger somehow? It's an error on their part, and a common one. A solar sail should use the solar wind, right? Except that the analogy isn't valid. Particle thrust is minor in the Earth-Moon system like it is everywhere else. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 29 Oct 92 16:45:07 GMT From: Gerald Cecil Subject: Swift-Tuttle Comet a threat to earth? Newsgroups: sci.space In article MGr@news.cso.uiuc.edu, jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: [ consequences of impact deleted ] >estimates, but it's important to remeber that as a comet, S/T has a much lower >mass and is much more fragile than a similarly sized asteroid. As such, it's >much less dangerous than an asteroid of the same size. According to Shoemaker & Shoemaker in ``The New Solar System'', Chap 21 ``Earth-crossing asteroids are rarely more than 3 km across, [so] most craters larger than 60 km [on Earth] probably result from cometary impact.'' But, this is obviously in disagreement with the K/T iridium detection, which implies an asteroidal origin if extraterrestrial. The Yucatan impact structure is estimated to be ~160 km across I recall. They also state that ``we suspect that the largest craters on Venus have been produced by comet hits.'' so the atmosphere doesn't appear to help much. Finally, S/T comes in at a much higher velocity -- 50 km/s vs 17.5 for an Earth-crossing asteroid (this from Shoemaker & Shoemaker). Well actually the vector sum, but still more energetic. Crater size still estimated at ~20x the diameter of the impacting fragment. --- Gerald Cecil cecil@wrath.physics.unc.edu 919-962-7169 Physics & Astronomy, U of North Carolina, Chapel Hill, NC 27599-3255 USA ------------------------------ Date: 23 Oct 92 02:21:00 GMT From: wlmss@peg.pegasus.oz.au Subject: UFO EVIDENCE VS. Carl Sagan Newsgroups: sci.space Marinov and the Jelly Fish > Robert E. McElwaine B.S., Physics and Astronomy, UW-EC < Reminds me of Stefan Marinov of Austria who ran a 3 page ad on pp 48-50 of New Scientist of 18 December 1986. Marinov had elegant maths to show how his unique machines worked. His ideas centered around truth, relativistic physics, gravity and electromagnetism. He had a great deal to say about prejudiced science and blind scientists - "jelly fish". It makes great reading. Several weeks later a brief letter to the editor convincingly showed the basic flaws in Marinov's science and politely and generously showed the author to be an eccentric crank. It is in fact unfair to compare Marinov with R McElwaine B.S. or indeed Marinov's work with R McElwaine's B.S.. Marinov has much more class. _Marinov to the World's Scientific Conscience_ gives good insight into the rare mind of the intelligent misfit. If lateral thinking gives results surely if these fruit loops were harnessed to logic they could drag productive research into unexpected new dimensions. Thank goodness I'm normal. How about you? Lawrie Williams ------------------------------ Date: 29 Oct 92 15:35:26 GMT From: John Black Subject: What does the "P/" mean in P/Swift-Tuttle? Newsgroups: sci.astro,sci.space I've been wondering why the names of comets are prefixed by 'P/'. What does the 'P/' signify? John Black. ------------------------------ Date: 29 Oct 92 15:23:59 GMT From: pbrown@uwovax.uwo.ca Subject: What does the "P/ " mean in P/Swift-Tuttle? Newsgroups: sci.astro,sci.space The P/ in P/Swift-Tuttle stands for Periodic. This class of comets includes all comets with periods less than 200 years (if I recall correctly). A small point about the possiblity of impact with the Earth - if we take ST to be about 10 km in diameter and friable in makeup the fact that the relative Earth-Comet speed at impact would be about 60km/s is worth noting. I think most estimates for comet-sized objects impacting the Earth assume prograde orbits - hence the energy involved in an ST collision would be something like 10 times as much as for a prograde comet of the same size. This I think could cause a K-T like event. While there saromany models of what will happen in such an event, ST is such an oddball comet (n terms of outgassing) that there is noo guarantee that it will have a makeup like P/Halley. Hence there is much uncertainty as to what might happen in a direct impact. Peter Brown peter@canlon.physics.uwo.ca ------------------------------ Date: Thu, 29 Oct 1992 15:07:02 GMT From: pbrown@uwovax.uwo.ca Subject: What does the "P/" mean in P/Swift-Tuttle? Newsgroups: sci.astro,sci.space In article , black@breeze.rsre.mod.uk (John Black) writes: > I've been wondering why the names of comets are prefixed by 'P/'. What does the > 'P/' signify? > > John Black. ------------------------------ End of Space Digest Volume 15 : Issue 357 ------------------------------