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, 19 Feb 90 01:47:11 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 19 Feb 90 01:46:39 -0500 (EST) Subject: SPACE Digest V11 #62 SPACE Digest Volume 11 : Issue 62 Today's Topics: Re: Why we would need a planet. The SPACE Digest -- an explanation Re: Why we would need a planet. Re: Launcher Deelopment Costs (Was Fun Fact) Re: Space Station Costs Re: HST damage in orbit Re: metric vs. imperial units Re: Recreation in Space Re: Why we would need a planet. Re: Why we would need a planet. Re: Why we would need a planet. Re: Why we would need a planet. ---------------------------------------------------------------------- Date: Sun, 18 Feb 90 12:53:34 PST From: pjs@aristotle.Jpl.Nasa.Gov (Peter Scott) Subject: Re: Why we would need a planet. rochester!dietz@rutgers.edu (Paul Dietz) writes: >>>(3) It is cheaper to maintain Earth than to disassemble it, but the >>>habitable surface you could produce by disassembly would be greater. >>>A future civilization running up against the resource limits of the >>>solar system might find disassembly worthwhile. >> >>See expansion argument above. I simply cannot believe that we'd know >>how to bust and rearrange planets but not how to do other stuff like >>steal from Jupiter or the Sun or the Oort cloud. > >Jupiter and the Sun have deeper gravity wells (and lots of fairly >useless hydrogen and helium). This has to be the first time I have heard Paul Dietz refer to hydrogen and helium as "useless"... :-) Isn't it much more likely that this future civilization will use these two elements for power generation and possibly large-scale transmutation? You were proposing dismantling the Sun, that's a considerable gravity well and amount of hydrogen and helium! If the BIS Daedalus Project considered that the cheapest way to get He3 for their Barnard's Star probe was to mine it from Jupiter, this planet-munching culture should be capable of scaling up the same operation. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 18 Feb 90 21:29:28 GMT From: tm2b+@andrew.cmu.edu (Todd L. Masco) Subject: The SPACE Digest -- an explanation This time, I'll post here, rather than emailing to individuals. My apologies to readers of sci.space who aren't interested in these "overhead" details. The newsgroup sci.space is distributed along with the other USENET groups, passed from host to host, along "USENET feeds." Without a mail redistribution of some sort, direct connections to those sites are the only means by which those groups can be read. There is an extremely large number of sites that can be reached by mail that cannot get a direct feed, the majority of which can be reached by mail along the internet or the BITNet (For the purposes of this explanation, just consider them two different networks along which mail can be sent; It's really a little more complicated than that, though). The SPACE Digest exists primarily to serve those who can receive mail but do not get a USENET feed (strangely enough, many of these sites are with NASA). A newsfeed at the University of California at Berkeley sends new messages from the sci.space newsgroup to andrew.cmu.edu, the site from which the Digest is sent. Mail to space+@andrew goes two places: to UCB to be posted, and to the same directory to which incoming sci.space message go. Every night, the digest is put together from those messages. It's then sent out to subscribers. All subscription requests should go to space-request+@andrew.cmu.edu; Mail to space+ goes straight to the sci.space newsgroup, and subscription requests are generally not welcome there (I'm working on a way to filter these out; It's not trivial, with the way the digest is written). I took over the Digest about half-way through the last summer; Before then, it was run by Ted Anderson, the author of the digest code. Past issues of both the Digest and Marc Ringuette's space-tech list are available by anonymous ftp from the directory 'space', the SPACE archives, at fed.expres.cmu.edu (one 's' in expres). There is also a directory called 'inbox' to which anonymous ftp has write access. Please feel free to drop anything related to the space effort there; I'll probably post another message to the newsgroup, requesting entries for the archives. Hope this has been helpful; Please email any further questions to me (tm2b+@andrew.cmu.edu) or to space-request+@andrew.cmu.edu. -- Todd Masco Moderator, SPACE Digest ------------------------------ Date: 18 Feb 90 21:48:43 GMT From: thorin!cassatt!leech@mcnc.org (Jonathan Leech) Subject: Re: Why we would need a planet. In article <21039@watdragon.waterloo.edu> jdnicoll@watyew.waterloo.edu (Brian or James) writes: > Using the Earth for industrial raw materials is probably going to irk the >population still using it as a homeland. So strip off the outer kilometer of the planet, move it to the inside of a cylinder, and spin it up to 1 G. Not enough raw material there to matter, and the Earthers will have the only part that's interesting to them. -- Jon Leech (leech@cs.unc.edu) __@/ ``The experiment must be wrong'' - Richard Feynman (as quoted by Eugen Merzbacher), upon hearing that experimental data did not agree with theoretical predictions. Feynman was correct :-) ------------------------------ Date: 17 Feb 90 16:20:56 GMT From: thorin!grover!beckerd@mcnc.org (David Becker) Subject: Re: Launcher Deelopment Costs (Was Fun Fact) In article <9002161511.AA00675@crash.cs.umass.edu> ELIOT@cs.umass.edu writes: > > Hogwash - *Anyone* can blow up seven people when playing with rockets. > You get 1000 "fly by night" companies launching cheap rockets and > soon enough one of them will land in New York City. A Columbian 747 recently landed in the wrong spot in New York. Commercial aviation continued without missing a beat. True, it didn't have any fuel left on board but the DC-10 that 'landed' in Chicago after take off in the '70s in Chicago had mucho fuel on board. Again commercial aviation just kept on flying. Commercial rocket companies should be able to keep on truckin' after a failure. David Becker Have you crashed your machine today? beckerd@cs.unc.edu ------------------------------ Date: Sun, 18 Feb 90 12:59:39 PST From: pjs@aristotle.Jpl.Nasa.Gov (Peter Scott) Subject: Re: Space Station Costs bfmny0!tneff@uunet.uu.net (Tom Neff) writes: >You know, the wall of a space station is neither a tin can nor a paper >bag -- it's a complex sandwich of thin layers enveloping a lot of wiring >and tubes. Anything that holes the enclosure with sufficient enthusiasm >to make an interior stowed "quick patch kit" worth a shirtsleeved >astronaut's time to deploy is also likely to play hell with Station >systems, and possibly spew some dangerous stuff around. Hmm, you'd hope that they designed the thing by routing essential conduits through interior walls... anyone know details? If they didn't, then one would presume that they possess evidence that either (a) the risk of significant meteor damage is minimal, or (b) anything that would hole an outer skin would also punch its way through at least a few interior walls as well, so that there wouldn't be any advantage to interior routing. I doubt this latter possibility, though. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 18 Feb 90 06:23:17 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: HST damage in orbit In article <316@cfa.HARVARD.EDU> wyatt@cfashap.harvard.edu (Bill Wyatt) writes: > There was an interesting article on ablation by atomic oxygen in Earth orbit >in a recent Scientific American. The corrosion rates they mentioned made HST >look *extremely* vulnerable - has this been considered in the HST design, and >if so what has been done to combat it? ... The HST design dates back to before the problem was understood. However, the exterior materials are mostly things that are not seriously affected, and I believe observation planning now includes a constraint reading roughly "do not point forward along the orbital velocity vector for any length of time" to protect the optics. -- "The N in NFS stands for Not, | Henry Spencer at U of Toronto Zoology or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 18 Feb 90 23:29:00 GMT From: mailrus!umich!caen.engin.umich.edu!stealth@tut.cis.ohio-state.edu (Mike Peltier) Subject: Re: metric vs. imperial units In article <1990Feb12.010632.12891@sics.se> pd@sics.se (Per Danielsson) writes: >In article <1294@otc.otca.oz>, gregw@otc (Greg Wilkins) writes: >> - To some extent, when designing physical systems, recurring decimal >> places can be avoided, hence round off errors can be reduced. > >This I don't understand. Why is any measurement system better than >another here? > >> - To do any sort of calculation by computer, metric is by far better than >> imperial, thus reducing the possibility of program error. > >This, too, I fail to understand. Computers don't care about >measurement systems. > >-- >Per Danielsson UUCP: pd@sics.se (or ...!enea!sics!pd) >Swedish Institute of Computer Science >PO Box 1263, S-164 28 KISTA, SWEDEN The units don't matter at all, you're right, but it's the numbers that count, so to speak. When you start getting funky numbers going into a calculation, such as 5280, 12, 212, 32, etc, instead of 1000, 10, 100, 0, etc, you start introducting the potential for computational errors caused by the facts that computers can only represent numbers with limited significance, and use mantissa/exponent notation. Seeing as how you're at an institute of Computer Science, you should know about this stuff -- dividing 5 by 212 gives you: 0.023584905... Which a computer could only represent to a certain number of significant digits, and if you pile up those approximations, they will eventually throw your result off by a significant degree. However, if you divide 5 by 100, you get, very simply, 0.05, which is well within any computer's capability to represent exactly. Subtractive cancellation, round off errors, etc... Anytime you get long strings of decimal numbers, these little mosters are bound to catch up with you. -- - - - - - - - - - Michael V. Peltier | Computer Aided Engineering Network 1420 King George Blvd. | University of Michigan, Ann Arbor Ann Arbor, MI 48104-6924 | stealth@caen.engin.umich.edu ------------------------------ Date: 19 Feb 90 04:31:02 GMT From: calvin.spp.cornell.edu!richard@cu-arpa.cs.cornell.edu (Richard Brittain) Subject: Re: Recreation in Space In article <13883@cit-vax.Caltech.Edu> jerbil@csvax.caltech.edu (Joseph Beckenbach) writes: > ... and when it first happens in space, think of the list of journals >waiting for the resultant papers... :-) A little judicious work with more >popular magazines could even help highlight the romance (;-) of space. :-) :-) >"Marital Relations and Relationships in Zero Gravity" rewritten as >"Playboy/Playgirl Exclusive: Out-of-this-world Lovemaking" :-) ^3 > A few months ago a rather good spoof of a NASA technical report on the subject appeared in alt.sex. From the ensuing discussion of whether or not it was real, I decided there must be very little common readership between the two groups. Richard Brittain, School of Elect. Eng., Upson Hall Cornell University, Ithaca, NY 14853 ARPA: richard@calvin.spp.cornell.edu UUCP: {uunet,uw-beaver,rochester,cmcl2}!cornell!calvin!richard ------------------------------ Date: 19 Feb 90 00:58:06 GMT From: stan!katmandu!stevem@uunet.uu.net (Stephen Matson) Subject: Re: Why we would need a planet. In article <1533.25ded66c@csc.anu.oz> dxb105@csc.anu.oz writes: >In article <26033*@rpi.edu>, jimcat@itsgw.rpi.edu (Jim Kasprzak) writes: >> People who considered our planet of origin >> to be useless and disposable would probably no longer be human. > >In your experience, how do most people feel about the East African grasslands? And we are no longer four foot tall apes, are we ? -- E-mail == stevem@Solbourne.COM "FRODO LIVES" "COLORADO!!" -------------------------------------------------------------------------------- U.S. OUT OF NORTH AMERICA ------------------------------ Date: 18 Feb 90 19:39:38 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!watserv1!watdragon!watyew!jdnicoll@tut.cis.ohio-state.edu (Brian or James) Subject: Re: Why we would need a planet. Using the Earth for industrial raw materials is probably going to irk the population still using it as a homeland. There could well be more people living in non terrestrial habitats in a millenium or so (Although I doubt it myself, if the "It's raining chicken soup" crowd is correct about the wealth of NT habitat cultures. Rich people don't have kids.) but if there *are* more Habitat types than terrans, I would bet that most of the significant population growth occured because of habitat birth rates rather than the hordes of terrans emigrating up the gravity well. The logic of totalling the planet to make way for a 'higher' civilization may not be as self obvious to people who have lived their entire lives on a planet as it is to orbiting foreigners looking for a few decades of fast growth material. It's a lot like North Americans telling England "So sorry, but we're going to grind up Great Britain because we need the raw materials to feed our Detroit car factories. Hope you don't mind moving" or Japan saying the same to North America. A perfectly logical point of view, but only for people who don't come from the place they want to destroy.nd as I said earlier, most people's kids probably won't get to go upstairs. There are also places that are regarded as holy ground even for those who don't live there. How likely is it that space living Islamics would consent to dismantling Mecca? James Nicoll ------------------------------ Date: 19 Feb 90 00:56:13 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Subject: Re: Why we would need a planet. In article <9002182053.AA12315@aristotle.jpl.nasa.gov> pjs@ARISTOTLE-GW.JPL.NASA.GOV (Peter Scott) writes: >>Jupiter and the Sun have deeper gravity wells (and lots of fairly >>useless hydrogen and helium). > >This has to be the first time I have heard Paul Dietz refer to hydrogen >and helium as "useless"... :-) Isn't it much more likely that this >future civilization will use these two elements for power generation and >possibly large-scale transmutation? You were proposing dismantling the Sun, >that's a considerable gravity well and amount of hydrogen and helium! Well, I was thinking of raw materials for building structures. Hydrogen and helium are, by themselves, pretty useless for that (although compounds containing hydrogen might very well use material mined from the outer planets at that point). Large scale transmutation would necessarily involve even more energy than mining matter from the sun, so (by that measure) would be less practical. Transmutation does look to me to be feasible for making some rarer isotopes, though, even with current physics, given a sufficiently large spacefaring civilization. >If the BIS Daedalus Project considered that the cheapest way to get He3 for >their Barnard's Star probe was to mine it from Jupiter, this planet-munching >culture should be capable of scaling up the same operation. 3He is a special case, since the earth has almost none of it. The alternative in the Daedalus Project study was to make the 3He by nuclear reactions. The situation is reversed for heavy elements: on Earth they can be stripped from the surface, while on Jupiter they are in the core. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 19 Feb 90 00:54:23 GMT From: stan!katmandu!stevem@uunet.uu.net (Stephen Matson) Subject: Re: Why we would need a planet. In article <1990Feb17.224335.26238@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes: >(3) It is cheaper to maintain Earth than to disassemble it, but the >habitable surface you could produce by disassembly would be greater. >A future civilization running up against the resource limits of the >solar system might find disassembly worthwhile. > Aw C'mon, Your talking like the Earth was an old Ford or something. You know it is MUCH cheaper to dump toxic waste in the local pond then to try to refine it. Don't bring the birth place of countless millions of species down to a level of costs, products and efficiency. I know this is a hypothetical situation we are talking about but you scare me. I hope you don't pass your ideas about the dispensability of earth to your kids. Besides you ideas are a little off. By the time we could use up ALL the resources in the solar system we would be traveling hundreds of light years from this little place called home. -- E-mail == stevem@Solbourne.COM "FRODO LIVES" "COLORADO!!" -------------------------------------------------------------------------------- U.S. OUT OF NORTH AMERICA ------------------------------ End of SPACE Digest V11 #62 *******************