Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Mon, 30 Oct 89 03:25:27 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 30 Oct 89 03:24:58 -0500 (EST) Subject: SPACE Digest V10 #174 SPACE Digest Volume 10 : Issue 174 Today's Topics: Re: Try thinking before stinking RE: SPACE Digest V10 #157 Re: Neptune images on CD-ROM from NASA Re: Halley's Comet Re: Asteroids as Weapons... Re: Asteroids as weapons of mass destruction Exhaust velocity ---------------------------------------------------------------------- Date: 22 Oct 89 14:18:00 GMT From: mirror!frog!john@CS.BU.EDU (John Woods) Subject: Re: Try thinking before stinking In article <2524@uceng.UC.EDU>, dmocsny@uceng.UC.EDU (daniel mocsny) writes: > In article <2137@frog.UUCP>, john@frog.UUCP (SuperUser) writes: > > In article , cr10+@andrew.cmu.edu (Christopher John Rapier) writes: > > > Face it, mans greatest accomplishment pales in comparison to the > > > beauty and marvel of a leaf of grass. > > > > Does it? Why do you say that? > > No human artifact equals the living cell in information storage > density, and the abilities to self-repair and self-replicate. I first want to point out that my basic desire was to point out an oft-repeated but never-examined assumption, in hopes of getting some examination. To continue playing Devil's Advocate, however: a blade of grass has had two billion years to get it right; if it didn't work so well, it wouldn't work at all. I tend to marvel at the unexpected, not at the required. As far as beauty goes, it is simple arrogance to state that a blade of grass MUST BE more "beautiful" than the Shuttle, because beauty is a question of definition, not of natural law. If you want to demand that beauty and marvel are equivalent to complexity, (not at ALL an obvious specification) then I respectfully request that the judging be delayed for two billion years, to give the newcomers a chance to catch up. And I demand that the newcomers HAVE that chance to catch up. -- John Woods, Charles River Data Systems, Framingham MA 508-626-1101 ...!decvax!frog!john, john@frog.UUCP, ...!mit-eddie!jfw, jfw@eddie.mit.edu ------------------------------ X-Delivery-Notice: SMTP MAIL FROM does not correspond to sender. Date: Sun, 22 Oct 89 21:20 CST From: BAWOLTERS%UALR.BITNET@VMA.CC.CMU.EDU Subject: RE: SPACE Digest V10 #157 Please remove me from this list... Thank you! ------------------------------ Date: 23 Oct 89 13:19:21 GMT From: gem.mps.ohio-state.edu!ginosko!shadooby!terminator!um.cc.umich.edu!Gavin_Eadie@tut.cis.ohio-state.edu (Gavin Eadie) Subject: Re: Neptune images on CD-ROM from NASA In article <8145@microsoft.UUCP> brianw@microsoft.UUCP (Brian Willoughby) writes: > I read in a recent computer weekly rag that NASA has released the images > that were downloaded from the recent Voyager flyby of Neptune. Which "computer weekly rag" was it and what date? I think we'll find that, though the Voyager Uranus and Satern encounter pictures are available on CD-ROM (and very nice they are too), the Neptune and Jupiter images are not yet printed. --- Gavin Eadie, Associate Director/Software Engineer The University of Michigan Computing Center 535 West William Street, Ann Arbor, Michigan 48109-4943 (313) 936-0816 ------------------------------ Date: Mon, 23 Oct 89 14:57:47 From: Lutz Massonne (+49-6151-886-701) Subject: Re: Halley's Comet The results of the Halley Space Probes can be found in several scientific publications. The first results had been published in Nature, Vol. 321 (1986), No. 6067, pages 259-366. These pages had later been published separately by Nature as a supplement. The results contained therein are the very first and mostly straightforward findings, some of which have later been corrected or re-investigated. The next source I am aware of the the proceedings of the 20th ESLAB symposium on the exploration of Halley's comet held in Heidelberg, W.Germany on October 27-31, 1986. These proceedings have been published by the European Space Agency as Special Publication ESA SP-250, a three-volume set of papers. (I think these papers have also been published as a book, but I will dig out the reference later.) In the near future Ellis Horwood limited (a British publisher) will publish "Comet Halley - Investigations, Results, Interpretations", a book which will (hopefully) contain some more recent information about Halley. In between there had been a conference in Brussels on comets which also gave rise to an ESA SP-xxxx publication, but I am not aware of its number. Regards, Lutz Massonne | | | Dr. Lutz Massonne, mbp Software & Systems GmbH, OAD, | | European Space Operations Centre, Robert-Bosch-Str.5 | | D-6100 Darmstadt, FRG | ------------------------------ Date: 23 Oct 89 17:27:23 GMT From: mm79+@andrew.cmu.edu (Mark Madsen) Subject: Re: Asteroids as Weapons... I forwarded this because it seems to have some relevance to the topic: From: Brian Preble Subject: Well Dressed for Disaster (forwarded from William Shotts) 15-Oct-89 3:20:58-GMT,6190;000000000001 Return-Path: <@po2.andrew.cmu.edu:ws1r+@andrew.cmu.edu> Received: from PO2.ANDREW.CMU.EDU by EDDIE.MIT.EDU with SMTP (5.61/25-eef) id AA07943; Sat, 14 Oct 89 20:20:51 EST Received: by po2.andrew.cmu.edu (5.54/3.15) id for dave-barry@eddie.mit.edu; Sat, 14 Oct 89 21:20:26 EDT Received: via switchmail; Sat, 14 Oct 89 21:20:15 -0400 (EDT) Received: from mms.0.1.401.MacMail.0.5.CUILIB.3.45.SNAP.NOT.LINKED.pcs6.andrew.cmu.edu.rt.r3 via MS.5.6.pcs6.andrew.cmu.edu.rt_r3; Sat, 14 Oct 89 21:19:40 -0400 (EDT) Message-Id: Date: Sat, 14 Oct 89 21:19:40 -0400 (EDT) From: William Geoffrey Shotts Well Dressed for Disaster By Dave Barry I was going to do my Annual Fall Fashion Outlook, until I found out about these asteroids that might crash into the Earth and extinguish the human race. So I've decided to cover both topics, because we definitely want to "look our best" for fall even though it appears that DEATH ASTEROIDS ARE COMING. You probably think I'm kidding about this, but that's because you didn't read Page 3 of my August 19 newspaper. If you had, you'd have noticed a series of small brown spots where I spat my coffee out when I saw a headline that said: "Asteroid will fly close to Earth." This was followed by a short Associated Press story stating that a semi-large asteroid was going to barely miss the Earth by 2.5 million miles on the following Thursday. The story quoted Dr. Eleanor Helin, a planetary scientist at the Jet Propulsion Laboratory in Pasadena, Calif., as saying this was the third serious asteroid to whiz past us this year, possibly indicating that there's a "sizable population" of asteroids heading our way, which could be "devestating." The story ended with this cheerful quote from Helin: "It's the one we don't see that's going to kill us." I'm sure that your immediate reaction to this story is the same as mine, namely to ask: Who's making the journalism decisions these days? Radishes? I mean, here we have a reputable scientist announcing that the Earth is an upthrust target in an astronomical game of Whack-a-Mole, and the story gets stuck on PAGE 3. You want to know what was all over the fron pages that very same week? NEPTUNE. The news media and the scientific community were engaging in one of their periodic joy spasms over Voyager 2, the plucky little robot spacecraft that travels through the galaxy beaming back the exciting news that every planet it encounters is basically The Toxic Waste Dump From Hell. In this case, scientists were calling urgent press conferences to announce that Neptune has a lot of -- get ready -- methane. Yes. The very same gas that Mel Brooks used to film the legendary beans-eating scene in "Blazing Saddles." So what we have is scientists and journalists dancing far into the night to celebrate the thrilling news that Neptune is a large orbiting clot of flatulence, and meanwhile, on Page 3, the human race is coming within 2.5 million miles of Extinction City. You're probably saying, "Yeah, but 2.5 million miles is a long way." Well, Mr. or Ms. Smarty Pants, it just so happens that 2.5 million miles is "almost a whisker," in the words of the Jet Propulsion Laboratory's Helin, whom I called up in an effort to get even more depressed about this story. She assured me that "near-Earth asteroids" come along regularly, and that eventually there could be a collision. "Certainly it could happen," she said. "We continue to find more and more objects that are a threat to civilization." What happens if a big asteroid hits the Earth? Judging from realistic simulations involving a sledge hammer and a common laboratory frog, we can assume it will be pretty bad. Helin said that if we got hit by an asteroid the size of the one that just missed us, "it would be a pretty unpleasant time for mankind. It could be an extinction time." The good news, Helin says, is that if we see an asteroid coming, and we act quickly, we might be able to send a rocket out there armed with a bomb to destroy it. This made me fell a lot better, realizing that we have the competence and intelligence to pull off such a feat, until I remembered that the space program is currently under the leadership of the vice president ("Okay, sir, let's say this golf ball is the Earth, and this nine-iron..."). So the situation is still worrisome, extinctionwise, but I remain optimistic, and I'll tell you why: LEGS ARE BACK FOR FALL. Yes. This is the word from the Highest Fashion Authority, Vogue magazine, which describes legs as "The Body Part of the Year" in an article accompanied by photographs of extremely short designer outfits that look terrific on your typical professional model weighing slightly less that a box of Rice Krispies but that will of course make any normal woman look like the Queen of the Hooker Rhinoceroses. We're sorry, ladies, but this is what Vogue wants, and you're just going to have to accept it, the way you accepted giant clown pants, Herman Munster Model shoulder pads and extremely short hair apparently styled by Monsieur Henri's House of Intense Radiation. As regards the Fashion Outlook for us men, I was paging through GQ magazine, and it appears taht we're supposed to continue slicking our hair straight back and grimacing as though we had just been offered a nice steaming bowl of leech soup. Also, I noticed an advertisement for Old Spice that said -- I'm not making this up -- "Now your underarms can be where your head is at." Which could actually be true, when the asteroid gets here. (Reprinted from The Washington Post Magazine 10/1/89) ------------------------------ Date: 23 Oct 89 00:03:37 GMT From: cs.utexas.edu!mailrus!jarvis.csri.toronto.edu!me!radio.astro!helios.physics!griffin@tut.cis.ohio-state.edu (Prof. A. Griffin) Subject: Re: Asteroids as weapons of mass destruction Disclaimer: I am NOT professor Griffin. If you use "F", please check the attribution against the signature. In article <2643@ibmpa.UUCP> szabonj@ibmpa.UUCP (Nick Szabo) writes: >In article <1989Oct18.022646.17827@helios.physics.utoronto.ca> griffin@helios.physics.utoronto.ca (Christopher Neufeld) writes: > >> So, to use it as a weapon, you would have to arrange for it to hit the >>ground directly, without spiraling in through the atmosphere. Current >>technology couldn't put that sort of delta-v on an asteroid, unless it was >>already on a worrisome course. > >It's not a matter of delta-v. It's simply a matter of finding a trajectory >that directly intersects that of Earth. This involves timing and fine >adjustment, which we do very well today. > >The energy needed for collision-course is much less than the energy for >delivering an asteroid into Earth orbit. In fact, it probably lies well >within the current art: find an asteroid that is within .001 km/s delta-v of >collision course with Earth (just a matter of thorough search with ground- >based telescopes), nudge it with a few well-placed nuclear explosives, and >fine-tune the course with a few small chemical rockets. > Well, by my calculations, an object which is in a circular orbit at a distance of 1 astronomical unit from the sun will, after applying .001 km/s of delta-v, be in a slightly eccentric elliptical orbit. The maximum deviation of the ellipse from the original circular path is 20000 km, which is only half-way to geostationary orbit. I could believe 0.1 km/s, for which the original impact parameter would be about 2 000 000 km, which is roughly the margin of miss we got on that asteroid a few months ago. What's the best delta-v one could put on a 100m asteroid? Based on this, I don't believe that a mass large enough to be dangerous could be aimed to within 1000 km on the earth's surface, and that is clearly too large a miss to make a useful weapon. The guidance in this problem would be much different than that used in the planetary flybys. Anyway, we are postulating a booster capable of rendezvous with an earth-approaching asteroid, and delivering nuclear charges to aim it at a target on the ground, a project which would require several years from launch to impact at the target. It seems to me that it would be simpler just to take the nuclear charges, put them on the booster, and fire them into your target directly. It would take less time, have a lower chance of failure, cost an order of magnitude less, and would have higher accuracy. >A vertical, as opposed to a grazing or "spiralling" approach, is also easy. >The orbit needs to be reasonably eliptical compared to Earth's, and the >delta-v should be large enough (3-4 km/s?) to give a swift approach. > I don't understand this last sentence. What is your definition of delta-v here? Mine is the amount by which the asteroid's velocity is changed. >Legal and/or military steps will need to be taken as space development >progresses, to protect Earth from the high-energy activities of space. >Robert Heinlein started to discuss this 25 years ago in _The Moon is a Harsh >Mistress_. I don't know of any solution. This is a big problem. > Assume that we have a real space presence for this scenario. We'll have space telescopes much more capable than ground based ones available at present. A nuclear explosion anywhere in the line of sight of earth is likely to be seen, and the radio pulse from the explosion would probably be obvious if detonated anywhere in the solar system. A drive flare from a plasma thruster (MHD etc.) would also be obvious. So, it would be difficult to deflect an asteroid without anyone knowing. Question: would space telescopes like the HST be able to detect a 100m asteroid at distances, say, of 50 000 000 km, assuming it was deflected without anyone knowing? If not, would the HST be able to track an asteroid whose initial position was pinpointed by a nuclear flash? >On the constructive side, we might use collision with other objects (the Moon >or other asteroids) to radically decrease the amount of energy we need to >move asteroids into various desired orbits. Question: if two asteroids collide >at high speed, do they shatter, vaporize, or remain for the most part intact? >If good chunks of them remained intact, and the resulting trajectories could >be reasonably predicted, collision would be an inexpensive technique for >moving asteroids and comets into Earth, Mars, Jupiter, or whatever orbits we >desired. > At typical approach velocities for two independent objects in space, asteroids which collided head-on would be shattered. Anyway, predicting the trajectory of fragments would be utterly impossible. It depends intricately on the internal structure and fractures of the two asteroids, their rotations, their initial shapes, and several other parameters. A more practical scenario is a plasma thruster at continual low thrust, which is bounced off a few planets for most of the delta-v, for eventual injection into terrestrial or lunar orbit. My understanding is that the expected path of such a powered asteroid would run it past venus, and would take twenty years to bring it to high earth orbit. >There are an estimated c. 100,000 asteroids with a delta-v closer than the >lunar surface. > OK, I'll bite, what's the delta-v to the lunar surface in this definition? >Only a few of these have been discovered, and none are >regularly tracked. 100,000 gives us a large population of trajectories to >work with. The sensor and computational power needed to find and track all >these is large but should be undertaken to forestall a tragedy. I just >lived through a scary 7.0 earthquake. Some other folks in the Bay Area weren't >so lucky. Compared to an asteroid strike, the earthquake was incredibly >trivial. > Absolutely. >-- >-------------------------------------------- >Nick Szabo >uunet!ibmsupt!szabonj >These opinions are not related to Big Blue's > All right, I've been making sweeping statements on a topic about which I know very little. I am ready to be corrected. Ought I to be worried about the possibility of somebody sending an asteroid to collide with the earth, and hitting a target with no prior warning? By that question I mean, is it a plausible scenario? -- Christopher Neufeld....Just a graduate student | "Scotty..now _would_ cneufeld@pro-generic.pnet01.crash | be a good time!" griffin@helios.physics.utoronto.ca | - Pavel Chekov "Don't edit reality for the sake of simplicity" | ------------------------------ Date: 23 Oct 89 13:20:44 GMT From: eru!luth!sunic!mcsun!ukc!inmos!conor@bloom-beacon.mit.edu (Conor O'Neill) Subject: Exhaust velocity In article <1989Oct18.174154.23242@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In general, correct. For one thing, it's easier to build solid motors >in large sizes (i.e. high thrusts). For another, the average molecular >weight of the exhaust is higher, which is bad for getting maximum velocity >but good for getting maximum thrust. I've seen this said before (many times) but never with a simple explanation. My school physics seemed to imply that it is exhaust momentum which matters, not simply velocity nor molecular weight. Could someone please elaborate. -- Conor O'Neill, Software Group, INMOS Ltd., UK. UK: conor@inmos.co.uk US: conor@inmos.com "It's state-of-the-art" "But it doesn't work!" "That is the state-of-the-art". ------------------------------ End of SPACE Digest V10 #174 *******************