Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.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, 16 Jun 91 02:34:23 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sun, 16 Jun 91 02:34:15 -0400 (EDT) Subject: SPACE Digest V13 #657 SPACE Digest Volume 13 : Issue 657 Today's Topics: Re: Self-sustaining infrastructures Re: satellite refuelling Re: Calculating delta-V Re: Extra Terrestrial Intelligence Re: Calculating delta-V Re: Pregnancy in space (was Re: Rational next station design process) Re: Rational next station design process Re: Astrolabes Re: Moonbase movie *Plymouth* to air Sunday? Re: The Long Term Complete and utter nonsense from Nick Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 27 May 91 16:19:00 GMT From: sun-barr!newstop!exodus!concertina.Eng.Sun.COM!fiddler@apple.com (Steve Hix) Subject: Re: Self-sustaining infrastructures In article <1991May27.013344.27771@agate.berkeley.edu> fcrary@lightning.Berkeley.EDU (Frank Crary) writes: >> >I think refueling would be easier to do, even if it might be a less effecient >way to extend the lifetime of satellites. Replacing the station keeping >system would invlove, at least, screwing in bolts. Refueling just requires >connecting a hose. This would be easier to do teleroboticly, and may even >be possible with a satellite not designed for refueling (or failing that, >it would require very little re-design.) Refueling doesn't address the previously-mentioned problems with hydrazine catalysts. (So use something besides hydrazine...) There *are* other connectors besides bolts. Special tools to deal even with bolts reasonably in 0-g shouldn't be all *that* hard to come up with, though. How are electric thrusters coming along? -- ------------ The only drawback with morning is that it comes at such an inconvenient time of day. ------------ ------------------------------ Date: 27 May 91 02:42:30 GMT From: van-bc!rsoft!mindlink!a752@uunet.uu.net (Bruce Dunn) Subject: Re: satellite refuelling > dlbres10@pc.usl.edu writes: > Person: Fraering Philip > > Doesn't the design of some resistojets involve feeding the hydrazine > itself into an arcjet, without prior decomposition? I don't know about this. If you are going to dump a liquid into a resistojet, you are better off from a specific impulse point of view to use ammonia rather than hydrazine. Ammonia can be stored in tanks under its own pressure, eliminating the hardware associated with hydrazine tank pressurization. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: 29 May 91 01:44:16 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!uflorida!mailer.cc.fsu.edu!prism!ccoprmd@ucbvax.Berkeley.EDU (Matthew DeLuca) Subject: Re: Calculating delta-V In article <98181@lll-winken.LLNL.GOV> loren@tristan.llnl.gov (Loren Petrich) writes: > In "English" units, there is a unit of mass called the "pound" >and a unit of force called a "pound". Their ratio is the acceleration >of gravity, about 9.8 m/s^2. In this type of system, the ratio of >force to mass rate is measured in seconds, when it is really a >velocity, the effective exhaust velocity (EEV). Actually, the unit of mass in the English system is the slug. At one g, the weight of this unit is 32.2 pounds. -- Matthew DeLuca Georgia Institute of Technology "I'd hire the Dorsai, if I knew their Office of Information Technology P.O. box." - Zebadiah Carter, Internet: ccoprmd@prism.gatech.edu _The Number of the Beast_ ------------------------------ Date: 28 May 91 22:12:40 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!nic.csu.net!csun.edu!corona!swalton@ucbvax.Berkeley.EDU (Stephen Walton) Subject: Re: Extra Terrestrial Intelligence In article dlbres10@pc.usl.edu (Fraering Philip) writes (in reference to advance warning of supernovae): >Well, the combination of proximity given by interstellar travel and >more advanced science will probably give the colony plenty of warning >if the star is indeed about to blow up. It won't. The post-helium-burning stages of fusion in massive stars (fusion of carbon, neon, oxygen, and silicon) last less than 1,000 years each, much less than the Kelvin-Helmholtz time scale for the star's envelope. The time from the start of iron production to core collapse is less than 24 hours. At most, they'd get a few hours warning if they had neutrino detectors, because the neutrinos come straight from the core while the explosion has to propagate through the star's outer layers. References: "Supernovae" by Woosley and Weaver, _Annual Reviews of Astronomy and Astrophysics_, 1987 volume. "Supernova 1987A" by Arnett, Bahcall, Kirshner, and Woosley, _ibid_ 1990. -- Stephen Walton, Dept. of Physics & Astronomy, Cal State Univ. Northridge "Lately it occurs to me/What a long, strange trip it's been" ------------------------------ Date: 29 May 91 17:43:50 GMT From: prism!ccoprmd@gatech.edu (Matthew DeLuca) Subject: Re: Calculating delta-V In article <7585@mace.cc.purdue.edu> dil@mace.cc.purdue.edu (Perry G Ramsey) writes: >In article <30042@hydra.gatech.EDU> ccoprmd@prism.gatech.EDU (Matthew DeLuca) writes: >>Actually, the unit of mass in the English system is the slug. At one >>g, the weight of this unit is 32.2 pounds. >Well, sort of, but not really. Nobody uses the slug. Well, the only reason that I even know about the existence of the slug is that I learned a bunch of equations in one of my aerospace classes using slugs...the density of air was given in units of slugs per cubic foot. Gads. >Doesn't all this just make you want to puke? Hear hear. :) -- Matthew DeLuca Georgia Institute of Technology "I'd hire the Dorsai, if I knew their Office of Information Technology P.O. box." - Zebadiah Carter, Internet: ccoprmd@prism.gatech.edu _The Number of the Beast_ ------------------------------ Date: 29 May 91 18:51:43 GMT From: news-server.csri.toronto.edu!utzoo!kcarroll@uunet.uu.net (Kieran A. Carroll) Subject: Re: Pregnancy in space (was Re: Rational next station design process) In article <1991May28.174504.12087@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <1991May28.163205.12863@linus.mitre.org> sokay@cyclone.mitre.org (S. J. Okay) writes: >>... I would think that given the the fetus is already >>floating weightless inthe amniotic sac during its development, the absence of >>gravity wouldn't be that much of a problem (but then, I'm no MD either). > >Floating in fluid produces only approximate weightlessness. For example, >bones are still heavier than soft tissues, and have some small tendency >to try to sink. For that matter, the whole fetus probably doesn't exactly >match the average density of the amniotic fluid, and consequently will >feel some gravity. Whether any of this matters to development, nobody knows. An additional factor to consider crops up during labour and delivery. The presence of gravity is a perhaps-crucial factor involved in an about-to-be-born baby becoming "engaged" --- that is, the baby's head dropping down into the mother's pelvic cavity. Once this happens, the baby's head puts pressure against the mother's cervix. I was told in pre-natal class that this pressure is instrumental in triggering hormonal releases in the mother, that result in "effacement" (thinning) of the cervix, and eventually the beginning of cervical dilation (i.e. labour). Thus, gravity is instrumental in bringing on labour. This is a strong enough effect that particular postures and exercises are recommended for women whose babies don't become engaged naturally. If engagement doesn't occur properly, the result is usually a very long, hard labour, and/or a Ceasarian-section delivery. -- Kieran A. Carroll @ U of Toronto Aerospace Institute uunet!attcan!utzoo!kcarroll kcarroll@zoo.toronto.edu ------------------------------ Date: 29 May 91 23:39:16 GMT From: agate!lightning.Berkeley.EDU!fcrary@ucbvax.Berkeley.EDU (Frank Crary) Subject: Re: Rational next station design process In article <1991May29.123453.17598@eagle.lerc.nasa.gov> ecaxron@ariel.lerc.nasa.gov writes: >Well, there were a load of alternate designs looked into prior to signing >on to the original dual-keel, balanced (in terms of solar arrays), multi- >purpose, multi-module configuration. And that has been mentioned here >before. Most notably by Mr. Sheppardson, who will no doubt accuse me of >spreading misinformation again. I was unaware of these configurations. How funadmentally different from the final (or current) design were they? Were they all, for example, launched and supported/supplied by the space shuttle, used long sections of truss structure, etc? > ...And, if you want detailed design studies of all >proposed alternative concepts, the database would be *huge*. > While I agree agree that such a database would be too large to compile or use, this does not mean that it cannot be comprehensive. If, for example 20 possible designs, and thier estimated preformances/costs/etc..., were to be considered a reasonable sized database to work with, then these 20 designs should be as different as possible. If they are all permutations of the same basic concept (as for example, the "different" mission concepts in NASA's 90-study of manned Mars missions were,) then the full range of studied designs is too small for a good trade-off study. >...And keep in mind, although this is only my harmless >opinion, Lewis Research Center has gone a long way toward delivering a >working electrical power system for Fred: working end-to-end test beds, >a design selected for actuation of solar arrays, etc. The arrays themselves >have been designed and re-designed, and could be built - but proximity >operations considerations will delay this process for some time. To what extent are the Lewis solar pannels/power supply tied down to the specific design of Freedom? Would it be possible to use them, with only slight modifications, on totally different space systems? Frank Crary ------------------------------ Date: 30 May 91 00:39:50 GMT From: agate!lightning.Berkeley.EDU!fcrary@ucbvax.Berkeley.EDU (Frank Crary) Subject: Re: Astrolabes In article <5412@network.ucsd.edu> dmb@inls1.ucsd.edu (Doug Brownell) writes: >I was just introduced to a reproduction of a 13th century astrolabe >(I think that's what it's called), and was mightily impressed when it >accurately predicted the hour (to within +/- 5 minutes) based upon a >sighting of the sun (at ~3:30 pm) and knowledge of the date. Does >anyone know where such marvels can be purchased for less than a small >fortune? The one I saw was nearly $300 (gold electroplated), but the >design is so simple that there's got to be one for under $100, and >maybe even $50. I'd really apprecieat any leads as to where I might >search for one. As well as predicting the hour of the day, an astrolabe can do many other things: Calculate the time and azimuth of sunrise and sunset. Calculate the phase of the moon on any given date. Find the location of any star (but, unfortunatly not planets) marked on it, at any given time. Etc. The accuracy of the device depends on its size and quality. From your discription of the one you saw, I would guess that it was about 20cm in diameter. Astrolabes exist (or did once exist...) of up to 5 METERS in diameter, these were accurate to on the order of 10 min. of arc. As far as buying one, I do not know about the prices. But there are a few things to look for: The circles on the tympan (the part you hold in your hand) that mark lines of elevation above the horizon should NOT have a common center. The center of the 0 or 10 degree elevation line should be well above the center of the 70 or 80 degree elevation line. This is the easist way to see if the astrolabe was correctly constructed. If all these circles have a common center, then the maker did not know what he was doing. Also, the on the rete (the part that turns) there is a inner circle, with the dates of the year marked on it. The lengths of the months on this circle should NOT be of equal size (the ANGLES from the center of the astrolabe , not the center of the cricle, should be equal.) Good astrolabes are hard to find (at a good price espacially) these days. If you are into function as opposed to appearance, it is usually easier to construct your own using drafting tools and stiff cardstock. The following may be helpfull: Chaucer, Geoffrey (father of the poet) _A Treatise on the Astrolabe_ Ed. Walter W. Skeat, Oxford, 1872. Reprinted 1968. Gunther, Robert T., _Astrolabes of the World_ Oxford, 1932 North, John D., "The Astrolabe" Scientific American, January 1974 (96-106). Frank Crary ------------------------------ Date: 30 May 91 21:48:29 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!jarthur!petunia!zeus!jgreen@ucbvax.Berkeley.EDU (James T. Green) Subject: Re: Moonbase movie *Plymouth* to air Sunday? One piece of non-reality about "Plymouth" was the fact that so many people with absolutely no relevant background were sent to the Moon. It seemed that Plymouth was the only moonbase, or perhaps one of a few. With so many people here on Earth so willing to go into space, and dedicating their lives and careers to that goal, I find it extremely unbelieveable that a bunch of hicks would be sent. I was very annoyed by all the "was it right to come here" BS dialog that was being bantered about by some of the characters. I don't believe anyone who wasn't absolutely positive about the rightness of going would be *ALLOWED* to go (at least anytime in the next century). However, there was one character (the kid with the super moon buggy) who said that he "couldn't be pried (sp) out of here... every time an airlock opens, you're making history." I would have like a lot more of that kind of positive attitude throughout. Technically, it seemed OK. We could probably do it within 20 years (or less) if it could only get funded :-( -------------------------------------------------------- James T. Green, Innocent Bystander jgreen@eros.calpoly.edu ------------------------------ Date: 31 May 91 14:37:14 GMT From: usc!cs.utexas.edu!cse!texas!csl.dl.nec.com!baker@ucsd.edu (Larry Baker) Subject: Re: The Long Term henry@zoo.toronto.edu (Henry Spencer) writes: |> In article <1348@argosy.UUCP> kevin@locke.UUCP (Kevin S. Van Horn) writes: |> But what do you call it when a group of |> >venture capitalists finances a startup (like the one I'm working for -- MasPar) |> >with the expectation that they'll have to wait maybe five years to see a |> >return on their money? |> |> Medium term at best. Ask the Japanese. The 5-year plan is the "near-term" plan in our company. They don't openly discuss the mid-term or long term plans with us peons, but they exist. Someone once asked Mr. Morita, the CEO of Sony corp. how far in advance they (at Sony) plan. His answer was: "200 years." -- Larry Baker NEC America C&C Software Laboratories, Irving (near Dallas), TX baker@csl.dl.nec.com cs.utexas.edu!necssd!baker ------------------------------ Date: 1 Jun 91 04:09:58 GMT From: usc!wuarchive!rex!rouge!pc.usl.edu!dlbres10@apple.com (Phil Fraering) Subject: Complete and utter nonsense from Nick In article <1991May31.235412.61@sequent.com> szabo@sequent.com rants: >* The best cost estimate for a four-man station is $120,000 million >(GAO). It is unknown what Mir costs. A two man station requires the same >life support, refuelling, etc. equipment R&D and would not, I think, >cost significantly less than a 4-man job. Nick, a two man station will cost less than Skylab, which cost a lot less than 120 Billion. And our technology has *improved* since then. For those of you who don't remember the ancient history, Skylab was a three-man station. I remember reading all about it in the late seventies in _National Geographic_ (you know, that invertebrate "astronautist" rag?). The NG article was from the early seventies, but You are taking the life-cycle cost of a twelve-man station over thirty years with the most expensive booster possible (you mentioned 900 million per launch) needed four times a year for resupply as the startup cost of its four-man "construction phase" initial operations capability. And that for what many consider to be an extremely expensive and bad example of a space station. I think you know all this already, but blanket statements like "120,000 million for a four-man station... and a two-man station will cost just as much..." (not exact quotes, I know, but I can't stand to read the thing twice) sort of make you feel superior, don't they? Phil Fraering || Usenet (?):dlbres10@pc.usl.edu || YellNet: 318/365-5418 Standard disclaimer, whatever a disclaimer is, applies. ''It hardly mattered now; it was, in fact, a fine and enviable madness, this delusion that all questions have answers, and nothing is beyond the reach of a strong left arm.`` - Larry Niven and Jerry Pournelle, _The Mote in God's Eye_ ------------------------------ End of SPACE Digest V13 #657 *******************