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 ; Sun, 12 Nov 89 01:25:29 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sun, 12 Nov 89 01:25:07 -0500 (EST) Subject: SPACE Digest V10 #236 SPACE Digest Volume 10 : Issue 236 Today's Topics: RE: SPACE Digest V10 #233 Re: finally! Re: Vax to ride space shuttle. Re: Geostationary vs. Equatorial orbits Re: NASA Headline News for 10/26/89 (Forwarded) Re: Future Space Missions Re: Space Elevator fragility of life support Re: Geostationary vs. Equatorial orbits Re: Future Space Missions Re: COBE Press Kit (long) Re: Geostationary vs. Equatorial orbits ---------------------------------------------------------------------- Date: Sat, 11 Nov 89 16:21:23 -0900 Sender: Reply-To: From: "This sentence has thre erors." Subject: RE: SPACE Digest V10 #233 On the thread of "living in basements" The moon is both more and less hospitable than the place where I am living. As I type, it is -51'F outdoors with a WCF making it close to -70. To get on my bicycle and ride to work (a 90 minute ride) takes about 2 hours to dress and prepare. (I ride a bicycle because it is a much mroe reliable form of transportation for me in the winter...batteries don't die of exposure, the engine doesn't icce up, the radiator doesn't freeze....) Under that situation, the moon and interior Alaska are about as pleasant as one another. However, if one of my life support systems dies (woodstove, insulation, etc...) there is usually enough time for me to fix the problem without serious injury. On the Moon, there is no guarentee. There are two general reactions to a fragile personal environment. One is the "machismo" reaction espoused by so many of my fellow alaskans, the other is simply quiet acceptance... Yes, people can survive on the Moon, given the proper living quarters... No, I don't think we're anywhere close to being able to do it yet... Please remember, most of NASA's engineers live in beastly, uninhabitable places like Florida or Texas or Washington D.C. They don't have any intuitive grasp of climactic extremes, or the need for insulation...just like I personally, have no intuative feel for dealing with 100 degree weather with high humidity. It can be learned, however. On to some more details of building L-City: Vacuum makes a beautiful thermal insulator. It will be needed UNDER L-City...Such as a honeycomb of unpressurized cells under the city "foundation". One of the great difficulties of living in Alaska is that the ground saps heat MUCH faster than ambient air temperature. I have no idea if any analagous problems would exist on the Moon. However, you do have the advantage of virtually unlimited power on the moon for heating....and no wind chill factor. Ramblings courtesy of Ken Burnside/FSKWB@ALASKA/FSKWB@acad3.fai.alaska.edu ------------------------------ Date: 1 Nov 89 17:04:50 GMT From: littlei!nosun!snidely@uunet.uu.net (David Schneider) Subject: Re: finally! In article <1949@cs-spool.calgary.UUCP> rossd@acs-sun-fsf.UUCP (David Ross) writes: > The whole point of this meaningless tirade is, in short, that even if Mr. >Spencer is NOT the absolutely first person to tell _YOU_ about something, >and even if he is not the first person to tell most people, there are still >going to be a few of us who do appreciate hearing about it from SOMEBODY. > It also adds to the sense of completeness for those reading the progress of the preparation, launch, and mission. And some of us do lose track of news on the conventional media (radio, TV). Dave Schneider Intel Scientific Computers ------------------------------ Date: Sat, 11 Nov 89 22:51:33 EST From: "Keith F. Lynch" Subject: Re: Vax to ride space shuttle. To: "gateh%CONNCOLL.BITNET@VMA.CC.CMU.EDU"@MINTAKA.lcs.mit.edu Cc: KFL%AI.AI.MIT.EDU@MINTAKA.lcs.mit.edu, space@andrew.cmu.edu > It ... is cooled by convection. How can that work in microgravity? Warm air wouldn't rise. ...Keith ------------------------------ Date: 11 Nov 89 17:55:48 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Geostationary vs. Equatorial orbits In article <23892@cup.portal.com> lsheldon@cup.portal.com (Laurence Larry Sheldon) writes: >OK, a question from the "F" row--I am not anything that starts with >"astro-" but I thought geostationary orbits _were_ equatorial orbits! Any truly geostationary orbit is equatorial. Other orbits, with equal 23:56 periods but nonzero inclinations, will have figure-8 shaped ground tracks centered at the equator and with a length that increases with inclination. Anyway, someone may have misread the discussion. We were talking about the cosmic background explorer (COBE) satellite which has a SUN SYNCHRONOUS, *not* geostationary, orbit. Sun synchronous is a near-polar orbit tweaked just enough so that the orbital plane precesses a degree/day to track the sun rather than the stars. The ground track of a sun-syncronous orbit zips all over the place. (However, it's always the same time of day underneath the satellite, which is why s-s orbits are popular with photo spysats.) -- "UNIX should be used :: Tom Neff or as an adjective." -- AT&T :: ...uunet!bfmny0!tneff (UUCP only) ------------------------------ Date: 11 Nov 89 23:09:05 GMT From: jarvis.csri.toronto.edu!utgpu!utzoo!henry@rutgers.edu (Henry Spencer) Subject: Re: NASA Headline News for 10/26/89 (Forwarded) In article <1745@syma.sussex.ac.uk> nickw@syma.susx.ac.uk (Nick Watkins) writes: >Now my question. CRRES is to ride an Atlas 1. What is the difference >between this and current Atlas Centaurs, and also what is an Atlas 2? This is the latest silly marketingspeak from General Dynamics. Fact is, almost nobody ever uses just a plain Atlas any more -- the Centaur is a standard fixture now. "Atlas 1" is the new marketing name for essentially an ordinary Atlas Centaur. Atlas 2 is a slightly souped-up version planned for the near future. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 12 Nov 89 00:17:20 GMT From: gem.mps.ohio-state.edu!wuarchive!mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!henry@apple.com (Henry Spencer) Subject: Re: Future Space Missions In article <5569@cbnewsh.ATT.COM> lmg@cbnewsh.ATT.COM (lawrence.m.geary,ho,) writes: >I have heard that Cassini will also use an Earth flyby to gain speed. >I assume this means that these probes are using underpowered boosters >and launching from the shuttle, as was the case with Galileo... > WHY in heavens name is JPL sticking to this method for probes planned > for far in the future?... >... Why aren't there plans to use appropriate boosters? Because there are none. Although it is fashionable to malign the Shuttle as a planetary launcher, the Shuttle/IUS combination is the heaviest booster available (outside the Soviet Union). Titan/Centaur is in second place by a considerable margin. Shuttle/Centaur would be better, Shuttle-C/Centaur would be still better, and a stretched-tank Centaur fuelled in orbit would be better yet... but the first was cancelled, the second is just a gleam in the planners' eyes, and the last isn't even being planned. The only available-now launcher that could do a better job on Cassini would be Energia. The Soviets have no superstitious fear of cryogenic upper stages, and they will happily quote a price to put 200 tons -- eight times the Shuttle payload, enough for a lot of Centaurs -- in low orbit using an 8-strapon Energia. If you're absolutely determined not to use something that hasn't flown, they'll quote a price for 75 tons or so using the off-the-shelf 4-strapon Energia. NASA is not going to ask. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 11 Nov 89 18:00:29 GMT From: mailrus!jarvis.csri.toronto.edu!me!radio.astro!helios.physics!neufeld@tut.cis.ohio-state.edu (Christopher Neufeld) Subject: Re: Space Elevator In _The Endless Frontier_ edited by Jerry Pournelle (Ace books, 1979) there is an article by Hans Moravec called "Cable Cars in the Sky". He discusses the currently available materials for making a geosynchronous skyhook, allowing for taper of the skyhook so that each segment of cable is just strong enough to hold the weight of the cable below plus payload. I quote without permission: p. 307 "Single crystal graphite whiskers with 50 times the strength to weight of steel have been grown in laboratories. Bulk material as strong would permit a synchronous cable with a taper of only 10, and a mass ratio of 400. Half this strength is perfectly adequate for an Earth synchronous skyhook." Sorry I don't have a more recent reference which might tell whether we can make these things in bulk now. A taper of 10 means that it is ten times thicker at synchronous orbit than at the ground and the ballast. A mass ration of 400 means that it can lift payloads weighing up to one four hundredth of the total mass of the cable. The taper is exponential in the weight to strength ratio. So, something with "half this strength" would have a taper of 100. The mass ratio would also roughly square. Other references: "Sky Stalk" by Charles Sheffield in _The Endless Frontier Vol II_ _The Inventions of Daedalus_ by David E. H. Jones p. 168 J. D. Isaacs, A. C. Vine, H. Bradner, G. E. Backus _Science_ 151, 682 (1966) Lvov _Science_ 158, 946 (1967) J Pearson Acte Astronautica 2, 785 (1975) J Pearson IAF Congress, Anaheim, Ca., Oct. 1976. AIAA paper IAF 76-123 J Pearson European Conference on Space Settlements and Space Industries London, England, Sept. 20, 1977 H. P. Moravec 23rd AIAA Meeting, The Industrialization of Space, San Francisco, Ca., Oct 18-20, 1977 also Journal of the Astronautical Sciences 25, Oct-Dec 1977 J Pearson AIAA/AAS Astrodynamics Conference, Palo Alto, Ca., August 7-9, 1978, AIAA paper 78-1427 H. P. Moravec _Skyhook!_, L5 News, August 1978 Most of these references reproduced from the bibliography in Moravec's article. So, what say we start now? -- Christopher Neufeld....Just a graduate student | "Out of my way, cneufeld@pro-generic.cts.com | I'm a scientist!" neufeld@helios.physics.utoronto.ca | - War of the Worlds "Don't edit reality for the sake of simplicity" | ------------------------------ Date: 12 Nov 89 04:05:18 GMT From: jarvis.csri.toronto.edu!utgpu!utzoo!henry@rutgers.edu (Henry Spencer) Subject: fragility of life support In article writes: >... Under that situation, the moon >and interior Alaska are about as pleasant as one another. However, if >one of my life support systems dies (woodstove, insulation, etc...) there >is usually enough time for me to fix the problem without serious injury. >On the Moon, there is no guarentee... The answer to this is obvious: systems which can suddenly "fail hard" must be fixed to either fail more slowly or fail soft. (Just hoping they won't fail is not acceptable for long-term habitation; they will.) Actually, most life-support system failures for a lunar colony *are* either slow or soft, just like on Earth. The bad ones are catastrophic loss of pressure (use multiple walls and compartmentalization), sudden major loss of hard-to-replace fluids (gas or liquid) into vacuum (same solutions), and sudden massive contamination of the rather small ecosystem by toxic materials (compartmentalization, plus extra precautions in areas handling toxic materials). It should be possible to handle most everything else with the same approach used on Earth, i.e. repair of broken systems plus sufficient reserves to survive transient failures. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 11 Nov 89 22:02:11 GMT From: cs.utexas.edu!ut-emx!walt.cc.utexas.edu!wastoid@tut.cis.ohio-state.edu (Feulner ... Matthew Feulner) Subject: Re: Geostationary vs. Equatorial orbits This is just for completeness: In article <14899@bfmny0.UU.NET> tneff@bfmny0.UU.NET (Tom Neff) writes: >In article <23892@cup.portal.com> lsheldon@cup.portal.com (Laurence Larry Sheldon) writes: >>OK, a question from the "F" row--I am not anything that starts with >>"astro-" but I thought geostationary orbits _were_ equatorial orbits! > >Any truly geostationary orbit is equatorial. Other orbits, with equal >23:56 periods but nonzero inclinations, will have figure-8 shaped >ground tracks centered at the equator and with a length that increases >with inclination. Right, There is a difference between geostationary and geosynchronous. Geosynchronous orbits just have the proper period. Geostationary orbits are geosynchronous with zero inclination. >Anyway, someone may have misread the discussion. We were talking >about the cosmic background explorer (COBE) satellite which has a >SUN SYNCHRONOUS, *not* geostationary, orbit. Sun synchronous is a (not necessarily) >near-polar orbit tweaked just enough so that the orbital plane "tweaked" meaning being at a certain inclination and altitude orbit so that the non-spherically-symmetric part of the gravitational potential acts to give it the correct precession rate. Mainly, J2 (the flattening) & J3 (the pear shape) of the spherical harmonic expansion. The Earth itself is the source of the precession. >precesses a degree/day to track the sun rather than the stars. >The ground track of a sun-syncronous orbit zips all over the place. >(However, it's always the same time of day underneath the satellite, >which is why s-s orbits are popular with photo spysats.) Matthew ------------------------------ Date: 8 Nov 89 14:16:09 GMT From: att!cbnewsh!lmg@ucbvax.Berkeley.EDU (lawrence.m.geary) Subject: Re: Future Space Missions In article <2086@jato.Jpl.Nasa.Gov> baalke@mars.jpl.nasa.gov (Ron Baalke) writes: > Future Space Missions > > o Cassini > Possible launch in 1996, orbiter would spend 4 years studying Saturn and > send an atmospheric probe into the moon Titan. > > o Fire and Ice > Possible launch in 2001, will use a gravity assist flyby of Earth in > 2003, and use a final gravity assist from Jupiter in 2005, where the > probe will split into its Fire and Ice components: The Fire probe > will journey into the Sun, taking measurements of our star's upper > atmosphere until it is vaporized by the intense heat. The Ice probe > will head out towards Pluto, reaching the tiny world for study by 2016. I have heard that Cassini will also use an Earth flyby to gain speed. I assume this means that these probes are using underpowered boosters and launching from the shuttle, as was the case with Galileo. This was done with Galileo because it was too late - or would cost too much, or the probe was too heavy - to refit the probe for launch on an ELV with a Centaur upper stage. But WHY in heavens name is JPL sticking to this method for probes planned for far in the future? Galileo will take six? years to reach Jupiter this way; it should have taken two. The other probes will likewise take years longer to reach their destinations by using this technique. Why aren't there plans to use appropriate boosters? --Larry -- lmg@hoqax.att.com Think globally ... Post locally att!hoqax!lmg ------------------------------ Date: 11 Nov 89 23:37:42 GMT From: jarvis.csri.toronto.edu!utgpu!utzoo!henry@rutgers.edu (Henry Spencer) Subject: Re: COBE Press Kit (long) In article <236@cfa.HARVARD.EDU> willner@cfa.HARVARD.EDU (Steve Willner) writes: >The one thing I wonder about is that the press release mentioned >eclipses; I don't see why there should be any in the IRAS-type orbit. >Maybe COBE is using a slightly different orbit (i.e. not exactly 90 >degrees to Earth-Sun line) for some reason... For a sun-synchronous orbit at a given altitude, ignoring one or two details, the inclination with respect to Earth's equator is fixed. A sun-synch orbit at practical altitudes is a few degrees retrograde. (If anyone is really interested, I can post the formula.) The orbital precession that makes the orbit sun-synchronous is caused by Earth's equatorial bulge, so orientation to the Earth is crucial. HOWEVER... that is with respect to the Earth's axis and equator, not with respect to the Earth-Sun line... and Earth's 23+ degree axial tilt means the two are *not* the same. A sun-synchronous orbit does have eclipses, especially in summer and winter when one of the Earth's poles is tilted well away from the Sun and satellites passing near it are therefore in shadow. I *think* there would be times in spring and fall when the bird would be in continuous sunlight -- I can't visualize it quite well enough to be sure -- but this definitely doesn't happen year-round. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 10 Nov 89 19:05:49 GMT From: portal!cup.portal.com!lsheldon@uunet.uu.net (Laurence Larry Sheldon) Subject: Re: Geostationary vs. Equatorial orbits OK, a question from the "F" row--I am not anything that starts with "astro-" but I thought geostationary orbits _were_ equatorial orbits! As I pondered-while-typing it dawned on me that I guess you could have a geostationary orbit at any latitude, but somehow is seems like an "orbit" directly over a pole would be undefined, so there must be some limit to how high a (in terms of latitude) a geostationary orbit can be. Is it possible to explain all that in terms that a survivor of high-school geometry and trigonometry, and college algebra can handle? ------------------------------ End of SPACE Digest V10 #236 *******************