Date: Thu, 12 Nov 92 05:10:46 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #415 To: Space Digest Readers Precedence: bulk Space Digest Thu, 12 Nov 92 Volume 15 : Issue 415 Today's Topics: Hubble's mirror IS SWIFT-TUTTLE THE REAL THREAT? Japanese X-ray satellite: Astro_D Jimmy Carter and Gerald Ford TV Commercial Lunar "colony" reality check Mars Simulation in Antarctica (3 msgs) NASA Coverup (2 msgs) Positioning Satellites? Study says: Space research spinoffs marginal Swift-Tuttle Comet a threat to earth? The story on Oxygen Was Re: Lunar "colony" reality check What kind of computers are in the shuttle? 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: 11 Nov 92 14:52:35 GMT From: "William H. Jefferys" Subject: Hubble's mirror Newsgroups: sci.astro,sci.space In article <1992Nov8.232547.27419@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: # #According to the NASA investigation of the Hubble mirror problem, there #was nothing wrong with the specs. The backup mirror built to the same #specs by Kodak is *perfect*. The problem was that Perkin-Elmer bollixed #up the testing of the figure of the mirror and ignored the results of #a Foucault test that showed the mirror to have spherical abberations #because their primary test was supposed to give more accurate results. #Unfortunately, they installed a fixture backwards when making the #primary measurements and got the *wrong* result. I'm pretty sure there was never a Foucault test; that there hadn't been one became an issue after the mistake was discovered. This was brought up at NASA reviews I attended. After all, the interferometric test was supposed to be so accurate that a crude test such as the Foucault test wouldn't tell you anything you didn't already know (or so they thought). The "fixture" that was used backwards was the Invar rod; It was indeed used backwards, but that was not the chief reason for the mis-manufactured null corrector. This was, as I posted earlier, the laser return from the end cap, which had had a fleck of black paint scraped off. Bill ------------------------------ Date: Thu, 12 Nov 1992 02:23:55 GMT From: Paul A Daniels Subject: IS SWIFT-TUTTLE THE REAL THREAT? Newsgroups: sci.astro,sci.space In <1992Nov6.092734.1@uwovax.uwo.ca> pbrown@uwovax.uwo.ca writes: >========================================================================= >The Comet Swift-Tuttle saga : an addendum - Duncan Steel, 1992 November 6th >One thing that no-one has picked up on so far, it seems, is that it is more >likely that an asteroid or comet big enough to wipe out mankind will hit >the Earth before P/ST may perchance clobber us on 2126 August 14th than >the probability of that comet itself doing the job. That was a mouthful, >but think about it: what I am saying is that even IF P/ST does hit the >Earth on that date there is a chance that we may have already been hit by >some other as-yet undiscovered object. >A very crude estimate of the chance of P/ST hitting, a priori (that is at >this stage without the observations to be made over the next decade) is >about 1 in 10,000. That is, the perihelion date is uncertain by about >25 days, and if it does come back so as to pass its node on 2126 August 14th >then since it takes about 3.5 minutes to cross the Earth's path and >24 hours = 400 x 3.5 minutes, more-or-less, the probability is about 1 in >25 x 400 = 10,000. >However, if there are about 3,000 Earth-crossing asteroids larger than 1 km >in size (that is about the size limit for a global catastrophe, depending upon >mass and impact speed) and these have a mean collision probability with our >planet of about 6 x 10^(-9) per year (see Steel & Baggaley, MNRAS, 212, 817, >1985) then one expects one impact by such an object every ~50,000 years. >[See also the discussion in the Spaceguard Survey report, ed. D. Morrison]. >That figure may be a little on the high (frequent) side, but I would plump >for one per 100,000 years as being in the right ball park. >This means that in the next century there is about a 1 in ~1,000 chance of >a 1 km asteroid dropping in to play (havoc). This is 10 times our current >estimate that mankind will be stuffed by P/ST in 2126. Note that no comets >(either SP or LP) have been included in my sum, and these may comprise >about 25% of the total risk (i.e. asteroids 75% of the hazard). Does that mean that we have a close flyby by one of these potential killers every 10 years? I would say that there is a good case for a fair bit of funding then.. Paul. ------------------------------ Date: Thu, 12 Nov 1992 04:09:21 GMT From: Robert W Murphree Subject: Japanese X-ray satellite: Astro_D Newsgroups: sci.astro,sci.space nousek@astro.psu.edu (John A. Nousek) writes: >The instruments consist of four conical foil X-ray telescopes >built by Pete Serlimitsos of Goddard Space Flight Center, two >X-ray CCD cameras built by George Ricker of MIT (with Penn State >Co-I's) and two gas scintillation proportional counters built >by Prof. Makashima of Tokyo University. The four telescopes >are coaligned and will simultaneously point at the observing >target, allowing both CCD cameras and both GIS counters to >collect data. Each mirror detector system has an effective >area around 400 cm^2, giving a total effective area greater >than Einstein, ROSAT or AXAF over most of the energy range. >Moreover the graze angle is smaller for these mirrors so they >retain large effective area up to 12 keV! (For reference >the Einstein mirrors dropped off at 3-4 keV, ROSAT at 2 keV >and AXAF at 9 keV). >The major limitation of these mirrors is that they are not >true imagers (i.e. they are right cone segments and not para- >boloid-hyperboloid pairs). This limits the spatial resolving >power to 1.3 arc min half power radius [although there is >a sharp core to the PSF which has been demonstrated to resolve >point source 36 arc sec apart.] The spectral resolution >of the detectors is quite good. The GIS has 8% energy resolution >at 5.9 keV, and CCDs have 120 eV resolution at 5.9 keV. The >energy band pass runs from 0.4 keV up to 12 keV. I gather that Astro-D is a superlative x-ray spectrometer. Is it "the first x-ray spectrometer" or only the first wiht with this wide and bandwidth, resolution, and apeture? Is the 1 arc minute resolution a significant handicap for many objects? What new capacities for doing science will it result in? Is this a "major" observatory like ROSAT and/or AXAF. I'm not the one to say, but for spectrometry it seems it may be a "major" observatory. Of course, it doesn't have to be a "major" observatory to do good science, and the fact that the japansese have launched 3-4 small missions in the x-ray band in 10 years may actually be much more significant in terms of science than a behemoth like AXAF that gets launched every 10-15 years or not at all. The US hasn't launched any free-flyers in the X-ray since HEAO or Eistein 10 years ago, have they? A few detectors on other people's satellites of course, but nothing big since Einstein. ` ------------------------------ Date: Thu, 12 Nov 1992 03:15:35 GMT From: Wesley D Scott Subject: Jimmy Carter and Gerald Ford TV Commercial Newsgroups: talk.politics.space,sci.space I saw a commercial with Jimmy Carter and Gerald Ford advertising the National Space Foundation last weekend. Does anyone have any more information? wesley@ecn.purdue.edu ------------------------------ Date: Thu, 12 Nov 1992 03:05:13 GMT From: "J. Lewis" Subject: Lunar "colony" reality check Newsgroups: sci.space,alt.sci.planetary In article fiddler@concertina.Eng.Sun.COM (steve hix) writes: >In article <1drh9aINN91n@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes: >> ... Yes, nitrogen has narcotic effects at high pressure, but so does >>oxygen. > >I think it's worse than that for O2: above two atmospheres or so, it's very >toxic. I don't have references to hand, but, from memory: above 2 atm or so, O2 is an acute and chronic neurotoxin; toxic, but in a different way than N2. Remember that O2, unlike N2, has some of the chemical properties of a free radical. Below *about* 2 atm, nearly all of the oxygen in the blood is complexed as oxyhemoglobin; above about 2 atm, the hemoglobin is saturated with oxygen, and O2 is present dissolved in the blood plasma. It is apparently this dissolved O2 that does the damage. As I say, from memory. I distinctly remember, though, seeing a paper about 20 years ago on chick embryos in hyperbaric O2, perhaps 20 atm; the effects of the O2 were comparable to those from high doses of gamma radiation. O2 is nasty, dangerous stuff; should be banned. ------------------------------ Date: Wed, 11 Nov 1992 22:45:44 -0500 From: Samuel John Kass Subject: Mars Simulation in Antarctica Newsgroups: sci.space "The Tartan", our school newspaper, has reported that the problem "can be fixed easily, but until it is, the project cannot be approved. Consequently, the date of departure for California en route to Antarctica will continue to be pushed back." Basically, Dante looks like a big, purple bug. It's transport counterpart, "Virgil" (which was dropped from the Antarctica mission due to manpower and time constraints) looked like a high-tech purple dune buggy with lots of extra wheels. The project was concieved of a year ago, and has already completed most final testing. It has some pretty neat features, including the ability to repel down steep slopes, and look around with a laser scanner. It's being worked on as a joint project with NASA and the NSF, who are interested in Mt. Erebus' analog to alien landscapes. If our newspaper reports anything new and exciting, I'll be sure to post again. --Sam -- Disclaimer: Everything is true. - sk4i+@andrew.cmu.edu -- -- A Math/CS major at Carnegie Mellon University -- Beward the fnords. -- ------------------------------ Date: Wed, 11 Nov 1992 23:24:24 -0500 From: Lawrence Curcio Subject: Mars Simulation in Antarctica Newsgroups: sci.space Is this rover the same robot we at CMU call, AMBLER? Big red sucker? Legs arranged like eggbeaters? ------------------------------ Date: Thu, 12 Nov 1992 02:05:15 GMT From: Frank Crary Subject: Mars Simulation in Antarctica Newsgroups: sci.space In article <1ds2aoINN1hp@gap.caltech.edu> kwp@wag.caltech.edu (Kevin W. Plaxco) writes: >> Later this season, NASA plans to send an eight-legged robot into the >>crater of Antarctica's Mount Erebus, the world's only easily-reached volcano >>with a permanent lava lake. >This is obviously some new definition of the phrase "easily-reached". How about, "within 25(?) miles of a United States Navy base?" Mt. Erebus is right next to MacMurdo station, which is a fairly sizeable establishment providing all the logistical support for American research stations in the Antarctic. Frank Crary CU Boulder ------------------------------ Date: Thu, 12 Nov 92 04:13:41 GMT From: amon@elegabalus.cs.qub.ac.uk Subject: Nasa Coverup > However,evidence gathered by the Apollo missions indicates that the > moon and earth differ greatly in composition. Scientists now tend to > lean toward the third theory - that the moon was "captured" by the > Earth's gravitational field and locked into orbit ages ago. There are > Not true. Current theory is based on supercomputer simulation that shows a final Mars sized planetisimal collision with earth created the Moon. Don't argue that here, go to the literature. There is loads of stuff on it. > planets in the solar system , is known to harbor life and a satellite > with this peculiar quality . The theory that the moon was placed here by > intelligent being(s) as a sort of "planet marker " , is only a theory . > As we all know , theories are not necessarily the same thing as > "Science." > True. There is no such theory and never has been. > 99 percent of moon rocks brought back turned out upon analysis to be > older than 90 percent of the oldest rocks that can be found on earth . If > we assume that the moon came from a different area of the solar system, > where the component material might have been different ,this assumption > would still not account for the disparity in the average age of the > matter composing the two bodies. > True, the rocks are older. The moon does not have plate tectonics. Very little of it's crust has been turned over since the late bombardment period. The Earth turns over oceanic crust in 100MY or so; other crust is bent, twisted, turned over, scraped along continental margins, uplifted, downlifted, sedimented, covered with lava, eroded by wind and water... Other than some central canadian; Australian; Greenland and central CSR(?) areas, very little old crust is available at the Earth's surface. > The dark areas on the moon are known as "maria" ,some of which form the > familiar "man in the moon". Maria are significantly absent on the far > side of the moon. The ones on the near side area consist mainly of lunar > soil and smaller rocks. Astronauts found it extremely difficult to drill > > Gravitational focusing is certainly one reason. There are other dynamical reasons as well. I'll let some astronomers explain it more accurately than I can. > Samples brought back to earth by both Soviet and American Space Probes > contain particles of pure iron. The Soviets announced that pure iron > particles brought back by the remote controlled lunar probe Zond 20 have > not oxidized even after several years on earth. Pure iron particles that > Ah, yes. Stainless steel. Iron and Nickel. That's what some asteroids are made of. You can buy pieces from the Barringer crater that are considerably older than that and are not rusted. I've held one in my hand. About 40KY old isn't it? > When the Apollo 15 astronauts used thermal equipment to measure > temperatures below the surface , they got unusually high readings, which > indicated high subsurface temperatures near the Apennine mountains. It > was speculated that , since the presumed density of the moon would > preclude the possibility of lava flows, magma and the like (volcanism has > never been observed on the moon) that the high readings could be > explained by highly radioactive elements just under the surface. > Actually, the amount of radioactive materials on the SURFACE of the moon > is "embarrassingly high" . Where did all of this hot ,radioactive > material ( uranium and thorium ) come from ? And if it came from the > interior of the moon (very unlikely) ,how did it get to the moon's > surface? > I know nothing about this, but if you are right, maybe I'll get rich before Nick Szabo :-) Nothing like fissionables for power and active magmatics for creating useable veins of minerals. > The few lunar excursions indicate that the moon is a very dry world. > One Lunar expert said that the moon was "a million times as dry as the > Gobi Desert" . The early Apollo missions did not even find the slightest > trace of water. But after Apollo 15, NASA experts were stunned when a > cloud of water vapor more than 100 square miles in size was detected on > the moon's surface. NASA officials suggested that two tiny tanks, > The lunar materials brought back are indeed hyperdry. There is no reason to believe that volatiles do not exist in permanently dark craters at the lunar poles. This has been a subject of debate on this digest for years. We all hope to see results from a lunar orbitting gamma ray spectrometer to settle it once and for all. As to clouds: there is an amateur astronomy group that studies Transient Lunar Phenomena. There could be lunar volcanic activities, venting and such. It is not the prevalent idea, but it does not break anyones models too badly if TLI prove to be real. That is the caveat. They might be venting or they might be lighting effects. We probably won't really know until we get "ground truth" from some of the areas where they are most commonly seen. It really is neither spectacular nor embarrassing. Again, if true, it would be damned useful. > Lunar explorations have revealed that much of the lunar surface is > covered with a glassy glaze , which indicates that the moon's surface has > been scorched by an unknown source of intense heat . Expert's analysis > shows that this did not result from massive meteorite impactings . One > explanation forwarded was that an intense solar flare, of awesome > proportions , scorched the moon some 30,000 years ago. Scientists have > remarked that the glaze is similar to the glaze created by atomic weapons > on earth soil. > I have heard no such thing. I have seen many pictures and have seen no such thing. The surface is grey dust that has been gardened by micrometeorite impacts for aeons. Again, the literature on this is wide and deep and has been much discussed here over the years because it is relevant to lunar resource extraction. I would suggest you start with the proceedings from the first Lunar Base Symposium. > In 1968 ,tracking data of lunar orbiters first indicated that massive > concentrations (mascons) existed under the surface of the circular lunar > maria. NASA even reported that the gravitational pull caused by themwas > so pronounced that the spacecraft overhead dipped slightly and > accellerated when flitting by the lunar plain , thus revealing the > existence of these hidden structures, whatever they are. Calculations > show that they are enormous concentrations of dense heavy matter centered > like a bull's eye under the lunar maria. NASA has never offered an > explanation of their existence. > You haven't been reading very much then. There is discussion of it in a number of texts I have read. I think "The New Solar System" was one with an excellent technical summary of lunar geology. Besides which, as was pointed out, the Earth has MASCONS too. There are gravity anomalies anywhere the crust is a bit thicker. Central mare are the impact sites of some rather large objects and were thereafter the site of massive flood basalts. Read that as: a great thickening of the crust. > 10. Is there anything "funny" about the moon? Yes. We should have bases there by now. ------------------------------ Date: Thu, 12 Nov 1992 00:25:35 GMT From: "Gregory N. Bond" Subject: NASA Coverup Newsgroups: sci.space,alt.conspiracy >>>>> On Sat, 7 Nov 1992 23:42:20 GMT, jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) said: Josh> Did you know that fully _half_ of all babies are born within one Josh> week of a full Moon! No kidding. And what is worse, half of those babies born within a week of a full moon have below-average intelligence! Obviously, the radiation from the alien artifact that is holding the moon up is affecting them. -- Gregory Bond Burdett Buckeridge & Young Ltd Melbourne Australia ``There is Faith, Hope and Charity. But greater than these is Banking.'' - 1492 ------------------------------ Date: 12 Nov 92 04:49:13 GMT From: Rich Kolker Subject: Positioning Satellites? Newsgroups: sci.space In article <1992Nov11.193843.8381@spuddy.uucp> chris@spuddy.uucp (Chris Allen) writes: > >Can anybody help me? (perhaps by telling me which group this *should* be in :) > >I have heard people mention a satellite or satellites whose signal enables >you to find your position wherever you happen to be. > >Can anybody tell me more - or point me to papers or references? > >many thanks, > > >chris allen. > >-- > > * Meeeow ! Call Spuddy on (0203) 638780/682331 for FREE mail & Usenet access * The Global positioning system will do just that. You can buy a receiver at any nautical supply or aviation supply house. I'm sure others will fill you in on the theory. ++rich ------------------------------------------------------------------- rich kolker rkolker@nuchat.sccsi.com It's been a long, long time -------------------------------------------------------------------- ------------------------------ Date: 12 Nov 92 04:48:04 GMT From: Gregory Aharonian Subject: Study says: Space research spinoffs marginal Newsgroups: sci.space,sci.econ Chance spin-offs are not a good enough reason for investing in space research, reports Germany's Fraunhofer Institute for Systems and Innovation Research, the ISI, in Karlsruhe. The ISI's analysis of patent citations concludes that space research produces no more - and perhaps fewer - advances in earth-bound technology than other areas of research. "Politicians have used spin-offs to justify funding for manned space flight", says Ulrich Schmoch, who led the project. "But the study's results mean they must now rely more heavily on direct, scientific arguments for space flight, like its usefulness in observing the Earth or repairing satellites". ISI researchers identified 3000 patents for advances in space technology filed since 1988, and then looked for patents that cited one or more of the source patents. Those that were for spin-offs into other fields numbered between 20 and 30 per cent of the original 3000. "It's difficult to express in percentages because the definition of a spin-off is subjective", says Smooch. The researchers used patent citation analysis because they thought it would be less biased than other methods, such as asking companies if they use space research. "The officials issuing the patents didn't know we were going to do a study", says Schmoch. When the ISI used the same method to investigate transfers from research on sensors for robots, it found three times as many spin-offs. According to the report, some space research, such as fittings for remote-controlled telescopic arms, heat-resistant materials and control technologies, did find other uses. Gas turbines, for example, can now operate at higher temperatures because the surface of the blades is treated by a process developed for space flight. The air-cooled motorcycle helment is an even more down-to-earth example, says Schmoch. The project was commissioned by the Federal Ministry of Research and Technology, but in 1990 responsibility for it was transferred to the German Space Agency, DARA. Although the study was completed in April, it remained under wraps until this month. Franz-Peter Spaunhost of DARA says the delay had nothing to do with the agency. "This is not a DARA study", he says. "It is something we inherited from the federal ministry". "In 1988, Germany didn't have the budgetary problems it does today", Schmoch says. "That's a recent addition to the discussion on whether to stop funding space flight". [New Scientist 10/31/92, 6] --------------------------------- Gregory Aharonian Source Translation & Optimization -- ************************************************************************** Greg Aharonian Source Translation & Optimiztion P.O. Box 404, Belmont, MA 02178 ------------------------------ Date: Thu, 12 Nov 1992 02:11:07 GMT From: Paul A Daniels Subject: Swift-Tuttle Comet a threat to earth? Newsgroups: sci.astro,sci.space If a comet like ST did strike the earth, what would the after effects be geologically? Would you end up with a large area of vulcanism? Would you end up with a hot spot? What would the the result of say a 5km dia. hole in the mantle? Paul. ------------------------------ Date: Thu, 12 Nov 1992 01:16:47 GMT From: David Knapp Subject: The story on Oxygen Was Re: Lunar "colony" reality check Newsgroups: sci.space In article <1992Nov11.222130.8652@infodev.cam.ac.uk> sl25@cus.cam.ac.uk (Steve Linton) writes: >In article <1992Nov11.143433.18514@news.weeg.uiowa.edu>, jboggs@umaxc.weeg.uiowa.edu (John D. Boggs) writes: >|> From article <1992Nov11.005151.15358@jpl-devvax.jpl.nasa.gov>, by jenkins@fritz (Steve Jenkins): >|> > >|> > Oxygen, like many gases, has narcotic effects at very high pressures, >|> > such as in deep-sea diving. It can cause blindness in newborns >|> > >|> >|> Yes to blindness in newborns, but it is the *nitrogen* that has the narcotic >|> effect in deep sea diving -- hence the use of helium for the really really >|> deep dives. > >Oxygen causes drunkenness-like symptoms above around 2atm. Any inert gas (except >helium, which I'll come back to) causes narcosis (anaesthesia) at sufficient >partial pressure. Roughly, the larger the molecule, the lower the pressure >needed. For nitrogen it's about 10atm, for ether or chloroform, less than 1. >Helium, presumably because of its very small molecule, causes the opposite effect >at very high pressure (> 50atm), causing trembling and over-excitation of the >nerves. Hence divers at great depths breathe mostly helium, with a few % >nitrogen to balance the effect of the helium, and less than 1% oxygen. Hydrogen >is also used, but I'm not sure of the details. Oxygen Poisoning: Oxygen is essential for life, so it may seem surprising that it can have poisonous effects; but this is important for divers to understand. The normal partial pressure of oxygen in air is 0.21 atm, equivalent to 21 percent oxygen at sea level. Above about 1/2 atmosphere (e.g., 50% oxygen at surface or 25% oxygen at 33ft), lung damage will develp within hours or days depending on the oxygen "dose". This is a recognized problem in treating hospital patients who need extra oxygen, but it seldom affects divers except in prolonged periods at depth in saturation diving or in extended recompression with oxygen breathing. More important for most divers is the fact that oxygen can cause convulsions, like th efits or seizures of grand mal epilepsy. Drowning is the usual result of an underwater convulsion, but the risk of convulsion selfom arises unless the partial pressure of oxygen approaches 2 atmospheres. Such a dose is reached with pure oxygen at 33 ft, 50% at 99ft, 20 % at 297 ft, etc. Convulsions may occur at lower pressures with excess carbon dioxide either inhaled or retained. There shoud be no possibility of oxygen poisoning in the use of open-circuit scugba unless charged with something other than compressed air. In most closed-circuit scuba, only pure oxygen can be used; and the depth of safe diving is severely limited. Special closed- and semiclosed- ciruit apparatus designed for gas mixtures must be used with great care to avoid oxygen poinsonin. The severity of the limits is illustrated by U.S. Nave rules which normally restrict the use of 100 % oxygen for working dives to no more that *25 ft* (the emphasis mine), with a 75 minute time limit at that depth. Limits permitted for unusual circumstances extend to 40 ft, where only 10 minutes are allowed. Taken from The New Science of Skin and Scuba Diving, by the Council for National Cooperation in Aquatics, New Century Publishers, 1980. Oxygen Poisoning: ...an excess of oxygen is just as bad as too little. If you breathe an excess of oxygen for an extended period of time, the outcome can be harmful. Excess oxygen can injure lung tissues and can adversely affect the central nervous system. Parial Pressures: How much oxygen is too much? This depends on three things: the amount, its pressure, and the exposure time. Ordinarily, we breathe a mixture of 78% nitrogen and 21 %g oxygen at atmospheric pressure (14.7 psi). Dalton's Law states that the total presssure of a gas mixture equals the sum of the partial pressures that make up the mixture. In other words, the sea level partial pressure of nitrogen equals 78 % of 14.7 psi, or 11.6 psi. The parital pressure of oxygen is 21 % of 14.7 psi or 3.09 psi. Now, oxygen poisoning can occur when the partial pressure of pure oxygen equals two atmospheres absolute, or 29.4 psi (two times 14.7 psi). This could happen if you were breathing pure oxygen (not air) at a depth of 33 feet. It could also happen by breathing ordinary air at a depth of 297 feet (this is where He-Ox mixes are used, with lower partial pressures of oxygen -d.k.), or 10 atmosphere (10 time 3.09 psi). Taken from Open Water Certification Sport Diver Manual by Jeppeson Co (used by PADI diver training) The bottome line is that we don't dive much beyond 100 ft on air. If we're going to go deeper, we get life insurance and use a helium oxygen mix with much lower fraction of oxygen. Helium is used as a buffer because it is not chemically reactive when it dissolves in the blood. I'm not sure if it dissolves less into blood than N2 but I know that decompression is still an issue using heliox mixes. Note that at Steve's upper limit of 50 atm, most people would have been long dead if they were using pure oxygen, so there's no need to worry about convulsions. All spelling errors are mine. -- David Knapp University of Colorado, Boulder Perpetual Student knapp@spot.colorado.edu Looks like hate *is* a family value after all and Colorado families are for it. ------------------------------ Date: 12 Nov 92 00:10:47 GMT From: Rich Kolker Subject: What kind of computers are in the shuttle? Newsgroups: sci.space In article <1992Nov11.175336.22450@access.usask.ca> choy@skorpio.usask.ca (I am a terminator.) writes: >The computers used to control the shuttle use very complex programs >that people don't want to rewrite for newer computers. Has any >upgrades been done or are the computers still the same old beasts? > >Henry Choy >choy@cs.usask.ca The shuttle computers have been upgraded. The joke around is that 1960's technology h has been replaced with 1980's technology, but they are a giant step forward. Now, if we can just get the money for the glass cockpit... ++rich : ------------------------------------------------------------------- rich kolker rkolker@sccsi.com It's been a long, long time -------------------------------------------------------------------- ------------------------------ id aa02875; 11 Nov 92 22:57:57 EST To: bb-sci-space@CRABAPPLE.SRV.CS.CMU.EDU Xref: crabapple.srv.cs.cmu.edu sci.space:51202 alt.sci.planetary:300 Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!drycas.club.cc.cmu.edu!pitt.edu!zaphod.mps.ohio-state.edu!caen!uvaarpa!murdoch!fermi.clas.Virginia.EDU!gsh7w Newsgroups: sci.space,alt.sci.planetary Subject: Re: Lunar "colony" reality check Message-Id: <1992Nov11.002243.20606@murdoch.acc.Virginia.EDU> From: Greg Hennessy Date: 11 Nov 92 00:22:43 GMT Sender: usenet@murdoch.acc.Virginia.EDU References: <1992Nov9.192439.1354@iti.org> <1992Nov10.152154.9709@eng.ufl.edu> Organization: University of Virginia Lines: 14 Source-Info: Sender is really news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU Henry Spencer writes: #Even so, nobody would have been rash enough to *predict* ice there. #Recent radar-mapping work shows strong echos from Mercury's poles which are #very difficult to explain as anything but ice deposits. The late Axel Firsoff has predicted ice on the caps of Mercury. However, Firsoff was known to have some "non-mainstream" ideas also. -- -Greg Hennessy, University of Virginia USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA Internet: gsh7w@virginia.edu UUCP: ...!uunet!virginia!gsh7w ------------------------------ End of Space Digest Volume 15 : Issue 415 ------------------------------