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, 8 Jan 1991 03:07:41 -0500 (EST) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 8 Jan 1991 03:07:10 -0500 (EST) Subject: SPACE Digest V13 #027 SPACE Digest Volume 13 : Issue 27 Today's Topics: Re: Information sources for frequent space questions (2 of n) Re: Interstellar Travel Re: solar cells Re: Interstellar Travel Re: solar cells Re: Interstellar Travel Re: Future Headlines Today Re: Solar cell factor/Space computers 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 ---------------------------------------------------------------------- Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 4 Jan 91 12:00:01 GMT From: usc!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!fuug!news.funet.fi!tukki.jyu.fi!jyu.fi!otto@ucsd.edu (Otto J. Makela) Organization: Turing Police, Criminal AI section Subject: Re: Information sources for frequent space questions (2 of n) References: <1991Jan2.123119.9520@nas.nasa.gov> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1991Jan2.123119.9520@nas.nasa.gov> eugene@nas.nasa.gov (Eugene N. Miya) writes: [Pioneer Venus 2] The main spacecraft bus burned up high in the atmosphere, while the four probes descended by parachute towards the surface. Though none were expected to survive to the surface, the Day probe did make it and transmitted for 67 minutes on the ground before succumbing to the intense surface heat. I only know what NASA tells me. :^) The truth of course is, a venusian Glorkz monster ate the probe. -- /* * * Otto J. Makela * * * * * * * * * * * * * * * * * * */ /* Phone: +358 41 613 847, BBS: +358 41 211 562 (CCITT, Bell 24/12/300) */ /* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE */ /* * * Computers Rule 01001111 01001011 * * * * * * * * * * * * * * * * */ ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: Fri, 4 Jan 91 08:05:07 PST From: thamilton@ch3.intel.com (Tony Hamilton, WF1-81, x48142) To: "space+@andrew.cmu.edu"@HERMES.intel.com, THAMILTON@ch3.intel.com Subject: Re: Interstellar Travel I am the fellow who started this thread a while back. Although I appreciate all of the response, no one has really answered my fundamental question. It is interesting to hear about fusion, antimatter, protons, etc., but I really would like to know specifically how all this is being applied to the problem of interstellar travel. Much of what has been said is simply theory. Is the USAF, NASA, or any other agency actually designing an interstellar craft? Anyway, I'll restate my original question, and add more: 1. Are there any viable designs for interstellar craft being worked on? 2. What speeds can be attained by various designs? I'm not a physicist, so I'd need an explanation on why there are limitations. Would ships be able to reach .1C, .5C, .9C, or what? 3. What are our closest interstellar neighbors? What do we know of them? Have we ever found possible planets orbiting neighboring systems? If not, do we have a good chance of finding such things? I know, these are some real specific questions, and probably require long explanations. Therefore, you might want to just E-mail me. Thanks Tony ******************************************************************************* * Tony Hamilton - Engineering Technician - Intel Corporation - 602-554-8142 * * - or - Sole Proprietor - Astral Gaming Enterprises - 602-834-5474 * * iNET === thamilton@ch3.intel.com "I think, therefore I am .... thoughtful" * * :::Astral Void BBS - 602-834-6065, mono-line, discussion/debate-300/1200::: * ******************************************************************************* ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 4 Jan 91 15:17:05 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1!watdragon!watyew!jdnicoll@ucsd.edu (Brian or James) Organization: University of Waterloo Subject: Re: solar cells References: <37487@cup.portal.com>, <88637@lll-winken.LLNL.GOV>, <37550@cup.portal.com> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <37550@cup.portal.com> Ordania-DM@cup.portal.com (Charles K Hughes) writes: (tons of RTG and nuclear power stuff deleted) >> And another possible difficulty with solar cells -- how much >>energy does it take to make them? They would not be too good if the >>amount of energy needed to make them was only equal to their output >>for several years of running. Has that question ever been addressed? > > If the energy is free, who cares how much it took to make them? *Sigh* Let's say that a solar cell takes 10 arbitrary energy units to make. Let's say it produces 9 AEU during its life. That means every time you install one, the net cost to the power production system is one AEU. Things that use up more of a resource than they produce do not, on the whole, make good sources for that resource. It's reasoning like Mr. Hughes' that gives the anti-nuclear folks a bad name. James Nicoll ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 4 Jan 91 17:00:12 GMT From: swrinde!zaphod.mps.ohio-state.edu!wuarchive!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Organization: U of Toronto Zoology Subject: Re: Interstellar Travel References: <9101041605.AA15306@hermes.intel.com> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <9101041605.AA15306@hermes.intel.com> thamilton@ch3.intel.com (Tony Hamilton, WF1-81, x48142) writes: >... Much of what has been said is simply theory. Is the >USAF, NASA, or any other agency actually designing an interstellar craft? None of them is even designing an interplanetary craft, never mind an interstellar one. Unless spaceflight can be pulled out of its current stagnation, it will be a long time before there is any need to think seriously about starflight. >1. Are there any viable designs for interstellar craft being worked on? Depends on what you mean by "worked on". Nobody is doing serious design studies; see above. Small-scale design speculation is being done here and there. The big problem is that any such design has to assume non-trivial advances in propulsion, and has to guess at what those advances will look like. >2. What speeds can be attained by various designs? I'm not a physicist, so >I'd need an explanation on why there are limitations. Would ships be able >to reach .1C, .5C, .9C, or what? There is no fundamental limitation except the speed of light, by current physics, and most propulsion schemes don't have specific limits either. However, 0.1c looks a whole lot more feasible in the near term than 0.9c, given that the energy requirements go as the square of velocity. (Energy is the dominant problem of starflight.) Multi-stage fusion rockets or straightforward antimatter rockets ought to be able to manage 0.1c-0.2c without too much trouble. 0.9c would need advanced antimatter engines and very large quantities of antimatter. >3. What are our closest interstellar neighbors? What do we know of them? Have >we ever found possible planets orbiting neighboring systems? If not, do we >have a good chance of finding such things? The closest star is the three-star Alpha Centauri system. Whether multiple star systems are a good bet for planets is unclear. Next out is Barnard's Star, which is small and faint; evidence for planets around it is now generally considered weak at best. One has to go somewhat further out, 10-15 light-years, to find really good-looking single stars. Nobody has positive evidence of planets around nearby stars, although the dust disk around Gamma Pictoris [? my references aren't handy] has been imaged. There has long been indirect evidence that most modest single stars have planets, and now there is increasingly strong spectroscopic evidence directly supporting this for nearby stars. -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 4 Jan 91 21:07:16 GMT From: sdd.hp.com!spool2.mu.edu!sol.ctr.columbia.edu!emory!wa4mei!ke4zv!gary@ucsd.edu (Gary Coffman) Organization: Gannett Technologies Group Subject: Re: solar cells References: <37487@cup.portal.com>, <88637@lll-winken.LLNL.GOV>, <37550@cup.portal.com> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <37550@cup.portal.com> Ordania-DM@cup.portal.com (Charles K Hughes) writes: > > I don't think the "allergy" is irrational given 3-mile island, >Chernobyl, lists of missing nuclear fuel, 55 gallon drums of nuclear waste Actually Three Mile Island showed that primary confinement works even in an induced loss of cooling accident. Chernobyl showed that even the worst scenario put up by the anti-nukes, core meltdown, *no* confinement, and a core fire for God's sake, didn't result in the fearmongers predicted mega-deaths. >> As to chemical poisons being decomposable, that depends on >>what kind of chemical poison. Heavy metals cannot be chemically >>decomposed. And some chemical poisons are difficult to decompose, such > > Heavy metals don't need to be decomposed - they can be refined and reused. So can nuclear fuels, but we're soooo scared we don't. >> I keep on being amazed by the anti-RTG movement. They complain > > What is RTG? Radioisotope Thermoelectric Generator. A completely sealed, no moving parts, no active control system, lump of radioactive material that gives off enough heat through natural radioactive decay to heat a thermopile enough to generate useful amounts of electrical power. >> So either solar cells or RTG's are the way to go for >>spacecraft. I presume that this is the standard argument. > > Hmmm...why not ground or space power generation for those satellites >that orbit the earth & moon? Deep space satellites are of little concern >here because once they leave, they're gone for good. Beamed power has been very strongly opposed by the enviornmentalists because of the supposed danger of the microwave power beam used to transmit the energy. Or were you planning to use a *really* long extension cord. > > RTGs (assuming they are small nuclear plants) are dangerous in any orbit >that decays before the nuclear fuel becomes non-radioactive. RTGs are designed to survive rentry without breaching their sealed shielding. The designs used have been exhaustively tested by actually sending dummy units up and causing them to renter. They work. >> And on the issue of safety, one should ask what kinds of >>critical tests are possible. It is much easier to perform really tough >>tests on an RTG than on a nuclear reactor, so one may feel more >>confidence in their safety. > > I still don't like the idea of a blob of nuclear goop falling from the >sky into my living room. :) Hook a couple of leads to it and run your computer off of it for a few years. Now that's a UPS! >> And another possible difficulty with solar cells -- how much >>energy does it take to make them? They would not be too good if the >>amount of energy needed to make them was only equal to their output >>for several years of running. Has that question ever been addressed? > > If the energy is free, who cares how much it took to make them? If it takes more fossil fuel to manufacture them than they will produce over their operating lifetime you care. And it does take more energy to manufacture them than they produce over their lifetime. They are net energy losers. Also the manufacture of solar cells requires some very nasty chemicals that must be disposed of after manufacture. > The real question (as I see it) is the *TRUE* cost. Burning fossil fuels >is cheaper than solar, nuclear is cheaper then solar, almost everything >is cheaper than solar if only the current fuel costs are looked at. If the >total cost of burning fossil fuels, using nuclear energy, etc is >totalled, solar will come out the clear winner. > >Charles_K_Hughes@cup.portal.com For solar cells the answer is a clear no on an energy basis and an enviornmental basis. For solar boilers driving freon turbines the energy cost is a net win. But the enviornmental costs are bad considering what the inevitable freon leaks will do to the ozone layer. Maintence costs in general are high since efficiency is very low and you need a lot of them to produce useful power. Perhaps the worst effect of using large scale solar energy to replace fossil fuels or nuclear plants is the effect on the climate. By placing large arrays of solar cells or solar turbines on the surface of the earth, you dramatically change the reflectivity of the earth in that area. A good solar collector absorbs almost all of the solar energy striking it and reradiates very little thus creating a hotspot in the local enviornment. The effects on the weather of the several hundred square miles of solar collectors needed to replace one nuclear plant should be spectacular. Gary ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 4 Jan 91 17:56:02 GMT From: sdd.hp.com!usc!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Organization: U of Toronto Zoology Subject: Re: Interstellar Travel References: <9101041605.AA15306@hermes.intel.com>, <1991Jan4.170012.4367@zoo.toronto.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu I wrote: >dust disk around Gamma Pictoris [? my references aren't handy] has been >imaged... Wrong Greek letter; it's Beta Pictoris. -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 1 Jan 91 13:10:02 GMT From: hpl-opus!hpcc05!col!hpldola!hp-lsd!oldcolo!burger@hplabs.hpl.hp.com (Keith Hamburger) Subject: Re: Future Headlines Today References: <1990Dec9.193204.8637@informix.com>, <20682@crg5.UUCP> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu Hear, Hear... All but passing a law, There are far too many laws already. Another option to consider would be to have NASA start to look at and analyze the competition from private sector proposals fairly, and based on such factors as accomplishment of mission designed for and RETURN ON INVESTMENT. (Well, I guess asking them to compare a positive cash flow to their own system fairly would be asking to much.) ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 1 Jan 91 20:26:02 GMT From: sdd.hp.com!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!censor!geac!torsqnt!lethe!telly!moore!eastern!egsgate!Maury.Markowitz@ucsd.edu (Maury Markowitz) Organization: EGS/Philo BBS Gateway, Toronto (416) 286-6191 Subject: Re: Solar cell factor/Space computers Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu >Depends; what do you mean by "spaceable"? Almost anything that >doesn't need convection for cooling can fly in the shuttle cabin -- >for example, Radio Shack Model 100s have flown unmodified. If Replaced by a Macintosh Portable as of late... >you're talking about use in an unpressurized satellite, you need to >worry a little about outgassing in vacuum and a lot about >temperature control. For long missions or critical applications, >you also need to worry about radiation effects, both gradual >degradation due to accumulated dose and transient hiccups due to >single particle hits. -- Any simply statements about the latter? I just read the former post about an amature satellite using Transputers (which are QUITE VLSI), but I was under the impression that the radiation effects were much greater for smaller devices. BTW, do normal CCD's outgas tremedously in space? Maury -- EGSGate Fidonet Gateway, Toronto (egsgate.fidonet.org) ...!{uunet, moore, lsuc}!eastern!egsgate ------------------------------ End of SPACE Digest V13 #027 *******************