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 ; Tue, 12 Jun 1990 01:44:50 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 12 Jun 1990 01:44:21 -0400 (EDT) Subject: SPACE Digest V11 #518 SPACE Digest Volume 11 : Issue 518 Today's Topics: Re: Missing mass Re: Lichens on Mars? 10 psi overpressure Incoming asteroids, how to move them with nukes. Re: T.A.F. -- Tough Apollo Trivia Re: Lichens on Mars? Nimbus-7 Update - 06/11/90 Re: Public Perception Of Space (was Re: US/Soviet Planetary Activity) Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 11 Jun 90 16:27:00 GMT From: sdd.hp.com!apollo!rehrauer@ucsd.edu (Steve Rehrauer) Subject: Re: Missing mass In article FORTMENU@tudsv1.tudelft.NL ("Nick A. van Goor") writes: >Here's the solution to the problem of the (until now) >missing matter in the universe. At long last, a logic, >yet subtle theory has emerged..... > >The mising matter all exists of disappeared socks..... Along those lines, I once read a rather amusing SF short story, in which a man tried to convince the world that we were being invaded by aliens which could perfectly mimic mundane items like paperclips, rubberbands, socks, etc. "Think of it," he would say, "No one pays heed to how many paperclips they have, nor raises an eyebrow when they turn up in odd places." In the end, he was discovered dead, with a coat-hanger wrapped tightly around his throat... You have been warned... :-) -- >>"Aaiiyeeee! Death from above!"<< | (Steve) rehrauer@apollo.hp.com "Spontaneous human combustion - what luck!"| Apollo Computer (Hewlett-Packard) ------------------------------ Date: 11 Jun 90 16:55:49 GMT From: mcgill-vision!quiche!calvin!msdos@BLOOM-BEACON.MIT.EDU (Mark SOKOLOWSKI) Subject: Re: Lichens on Mars? In article <4ae22b5c.20b6d@apollo.HP.COM> rehrauer@apollo.HP.COM (Steve Rehrauer) writes: > >Ah, no. Lichens would not grow under the conditions that various space >probes have shown us to (actually) exist on Mars, but that was back before >Dan Quayle revealed how habitable the planet wishfully is. > In fact, some alguaes and some worms can very well live on VEEEENNNUUUSSSS!!! Venus is certainly not the hostile hell our current mediatic propaganda and the mars/moon missions lobbyists are portraying! Mark S. ------- ------------------------------ Date: 11 Jun 90 14:47:18 GMT From: usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123!David.Anderman@ucsd.edu (David Anderman) Subject: 10 psi overpressure I seem to recall that the Challenger was destroyed by air pressure, rather than an explosion of the external tank. Wouldn't that indicate the overpressure in the payload bay was somewhat higher than 10psi? --- Opus-CBCS 1.12 * Origin: Universal Electronics, Inc. (1:103/302.0) -- uucp: David Anderman Internet: David.Anderman@ofa123.fidonet.org BBS: 714 544-0934 2400/1200/300 ------------------------------ Date: 11 Jun 90 22:06:13 GMT From: ox.com!kitenet!russ@CS.YALE.EDU (Russ Cage) Subject: Incoming asteroids, how to move them with nukes. [This thread comes from sci.astro, follow-ups are directed back there.] This is inspired by John Smith, ccopsjss@cc.brunel.ac.uk. [Speaking of whom, the less said the better, except that I have received mail from his site admin which indicates that we are not likely to be hearing too much from him in the future. I hope he takes a physics class.] Novice's Guide To Moving Your Asteroid (or, Nuke It Till It Goes). This is a treatment of the diversion of asteroids or other objects using nuclear explosives. It assumes knowledge of basic physics, such as conservation of energy and momentum. There is some guesswork involved here, since I do not have figures on everything; this guesswork is marked with "###". Perhaps some of the readers can fill in the holes with numbers. Footnotes are marked with numbers in parens, and follow the body of the text. BASIC METHOD The velocity of a small asteroid in space can be changed using nuclear explosives. Detonating a bomb nearby will cause the part of the asteroid exposed to the blast to be heated violently, vaporized, and ejected into space at high speed. The asteroid is pushed away from the bomb by the reaction. The push from any one bomb is small, but many can be used to effect significant changes in velocity. This can be used to, for example, change the orbit so that it misses, rather than strikes, the Earth. PART 1: THE BOMB Fission bombs release energy in many forms. CRC publishes these numbers for energy release from fission: Kinetic energy of fission fragments 82.5% < Blast Instantaneous gamma rays 3.5% < Blast Kinetic energy from fission neutrons 2.5% < Lost Gamma-rays from fission products 3.0% < Delayed Beta particles from fission products 3.5% < Delayed Neutrinos 5.0% < Lost In a bomb, only the blast energy is useful. Energy from neutrons, neutrinos and fission-product decay do not contribute to blast effects. This portion totals 14%. 86% of the total fission energy is available to drive blast effects. Of this portion, 96% is in the form of kinetic energy of the plasma and 4% is gamma rays. Most of the energy transferred to the asteroid (96%) will be as an extremely hot plasma, the vapor of the bomb itself. 4% of the energy will arrive as high- energy gamma rays(2), immediately before the plasma wave. A 100 kiloton explosion releases approximately 4.2e14 joules of energy. About 4.0e14 joules is plasma energy, and 1.7e13 joules is gamma-ray energy. PART 2: THE ASTEROID The asteroid is likely to be made of stone; stony asteroids comprise the majority of the ones known. This treatment will assume a density of 3.5 g/cc. Numbers for gamma-absorption will be assumed to be the same as for concrete(3) ###. Nickel-iron asteroids will be denser, carbonaceous chondrites and comets less dense. PART 3: THE EXPLOSION REACHES THE ASTEROID We will assume that the bomb explodes 100 m from the asteroid. (This may not be the optimal distance; it is used for the sake of argument.) To simplify the calculations, it will be assumed that a disc 100 m in radius on the asteroid is affected (where the bomb is up to 45 degrees from the zenith). 3/16 of the explosion energy strikes this disc. The gamma rays, moving at the speed of light, arrive first. They are absorbed very near the surface, 90% in the first 25 cm. At 100 m, the surfaces nearest the explosion will receive 1.4e8 J/m^2 of gamma energy. The top 25 cm absorb 5.4e2 J/cc of energy, or 1.6e2 J/gm. 3/16 of the total gamma energy hits the asteroid, or 3.2e12 joules. If the specific heat of the stone is the same as silicon dioxide (.3 cal/gm.deg C or less), this amount of energy will heat the stone by 500 degrees C or more. Silicon dioxide melts at ~1700 C. Therefore, the gamma rays from a single bomb will heat the top 25 cm of the asteroid's surface to glowing red heat. The gammas from further bombs will melt and then vaporize this hot material. On the heels of the gamma rays comes the plasma wave. The plasma deposits 3.3e9 J/m^2 of energy on the heated or molten stone. Plasma is absorbed in a very thin layer; ions do not penetrate deeply. Assuming that a layer 2 cm thick is heated uniformly ###, the surface rock (which will be molten, after the first few bombs) will absorb this energy, approximately 4.8e4 J/gm. This it is 30 times the energy required to melt the rock; the vapor expands into space. If the expansion is 50% efficient in con- verting heat to velocity ###, the "exhaust velocity" will be 6900 m/sec. The total energy is 7.5e13 Joules, and the mass of the vaporized rock is 1.6e9 gm (1600 tons). These quantities are all per bomb. By the time the 2 cm thick layer of rock plasma has become 2 meters thick, it has expanded by a factor of 100 and dropped in pressure by a similar amount. Since it loses almost all its starting pressure before becoming anywhere near as thick as its 100 meter radius, it can be assumed to expand as a plane wave rather than isotropically. This increases its propulsive efficiency. PART 4: THE EFFECTS The total impulse delivered to the asteroid per bomb is 1.6e6 kg * 6.9e3 m/sec = 1.1e10 kg-m/sec. A billion-ton asteroid will change its velocity by 1.1 cm/sec in response to this impulse. To change its velocity by 10 m/sec requires about 900 bombs of 100 kilotons yield each. PART 5: FEASIBILITY We have this many bombs. We have several times this many bombs. Delivering them is much more of a problem than availability. For instance, modern fusion bombs weigh about a ton per megaton of yield. This gives a total mass of about 90 tons for the 900 bombs. Add in booster rockets, radar and radio gear, and shields, and we are talking several hundred tons which must be launched from the ground into low-earth orbit. It's a big job, but not impossible. Call it a couple tens of Titan 4 launches, or a Saturn V or two. In other words, given the necessity and time to plan, we can do it. --- Footnotes: (1) CRC Handbook of Tables for Applied Engineering Science, 2nd ed. p. 433 (2) In the real world, some of the energy will be radiated as X-rays. These are absorbed in a thin layer at the surface, however, so it seems reasonable to count this X-ray enery with the plasma energy. The inaccuracy introduced will not be large enough to seriously affect the results of these calculations. (3) CRC Handbook of Tables for Applied Engineering Science, 2nd ed. p. 439 -- I am paid to write all of RSI's opinions. Want me to write some for you? (313) 662-4147 Forewarned is half an octopus. Russ Cage, Robust Software Inc. russ@m-net.ann-arbor.mi.us ------------------------------ Date: 11 Jun 90 13:15:50 GMT From: mcsun!ukc!icdoc!syma!nickw@uunet.uu.net (Nick Watkins) Subject: Re: T.A.F. -- Tough Apollo Trivia From article <1990Jun5.163718.23719@utzoo.uucp>, by henry@utzoo.uucp (Henry Spencer): > "Trouble plagued"? The F-1 development was, on the whole, fairly smooth, > and apart from a bit of a problem with pogo oscillation -- not uncommon > in new rockets -- it never gave the slightest trouble in flight. "Apollo", by Murray & Cox, now out in paperback, begs to differ and devotes a fair part of Chapter 10 to describing the efforts made at Rocketdyne in dealing with combustion instabilities in the F-1. Excellent book btw, as has been said already in this group. No trouble in flight though, as you say. Covers role of ex Avro Canadians (inc John Hodge ), among other many other little known aspects of Mercury/Gemini/Apollo history ... :-) Nick P.S. Anybody know how long it takes to fix an RL10 ... ? (the CRRES community waits with bated breath). -- Dr. Nick Watkins, Space & Plasma Physics Group, School of Mathematical & Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND JANET: nickw@syma.sussex.ac.uk BITNET: nickw%syma.sussex.ac.uk@uk.ac ------------------------------ Date: 12 Jun 90 04:10:52 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Subject: Re: Lichens on Mars? In article <1990Jun11.233553.19649@helios.physics.utoronto.ca> neufeld@physics.utoronto.ca (Christopher Neufeld) writes: >> Dream on!! Name me one Earth-based life form that lives at temperatures >>several hundred degrees above the boiling point of water. >> > Let's see if I can beat Mark to the 'answer.' How about that >ubiquitous example in the popular science press, the deep sea vent >micro-ecosystem? But the deep sea vent life *doesn't* live several hundred degrees above the boiling point of water. It exists in the surrounding, somewhat cooler water. There was a report some years back (in Nature) claiming that organisms had been found that grew in the vents themselves, at very high temperature. This proved to be an artifact. It is very unlikely that terrestrial life could exist at that temperature. Common biochemicals like glycine are destroyed in minutes under the conditions that exist in the vents. The upper limit of known terrestrial life is a few degrees above 100 C (certain archaebacteria that live in boiling pools). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 11 Jun 90 16:41:22 GMT From: swrinde!cs.utexas.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Nimbus-7 Update - 06/11/90 Nimbus-7 Update June 11, 1990 The Nimbus project declared a spacecraft emergency over the weekend when the project was unable to command the spacecraft transponder off due to antenna problems. The 9 meter antenna at Wallops was stuck in the Y-axis, and the 26 meter antenna (DSS16) in Goldstone, California, was then used to fix the problem, at which time the spacecraft emergency was lifted. The Hipparcos project was originally scheduled to use the 26 meter antenna, but with the European Space Operation Agency's (ESOC) concurrence, the antenna was freed up to support the Nimbus-7 emergency. _ _____ _ | | | __ \ | | Ron Baalke | baalke@mars.jpl.nasa.gov | | | |__) | | | Jet Propulsion Lab | baalke@jems.jpl.nasa.gov ___| | | ___/ | |___ M/S 301-355 | |_____/ |_| |_____| Pasadena, CA 91109 | ------------------------------ Date: 11 Jun 90 18:34:33 GMT From: att!cbnewsh!lmg@ucbvax.Berkeley.EDU (lawrence.m.geary) Subject: Re: Public Perception Of Space (was Re: US/Soviet Planetary Activity) In article <416@newave.UUCP> john@newave.mn.org (John A. Weeks III) writes: > >The only hope NASA has to rescue it's new Moon program would be to >send a mission to "the dark side" of the Moon. Maybe they could con >the public on this. After all, the commies have never seen the dark >side of the moon! 8-) In fact, they photographed it before we did. >Recently I was talking with a co-worker about the early history of the >shuttle. Another co-worker butted in and told me the "real" story >as he remembered it. NASA was dropping Shuttles off of a 747, but >they kept crashing because they couldn't fly. So they added rockets >to it to make it work. He knew this was true because he watched two >of the early lanuch attempts on TV. He obviously was confused with the >Enterprise glide tests. Oh well... And there are people today convinced that space launches cause rain, and that the Challenger was destroyed by God because they were searching for heaven. Such is the level of education in this country. >One thing that NASA could try is a TV show on network tv. How about >a 15 minute weekly or hour monthly show to give NASA news, mission updates, >behind the scenes views, and review past missions. NASA has their own cable channel. Who watches? You want a NETWORK show? You'll have to make it compete with "America's Funniest Home Videos". It's difficult to convey scientific subtleties when you have to degrade material to retain the attention of ill educated lamebrains. -- Larry Geary: 74017.3065@compuserve.com | Dislexics of the world, untie! lmg@mtqub.att.com | ------------------------------ End of SPACE Digest V11 #518 *******************