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, 9 Jan 90 15:59:25 -0500 (EST) Message-ID: <0ZeZ29e00VcJM2SU4x@andrew.cmu.edu> Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 9 Jan 90 15:58:50 -0500 (EST) Subject: SPACE Digest V10 #401 SPACE Digest Volume 10 : Issue 401 Today's Topics: Re: Simpler space suits? Re: Nuclear Reactors in Space Re: Simpler space suits? Re: Nuclear Reactors in Space Re: Nuclear Reactors in Space Re: Nuclear Reactors in Space Re: Nuclear Reactors in Space Re: Nuclear Reactors in Space Re: Nuclear Reactors in Space Re: Simpler space suits? Re: Nuclear Reactors in Space ---------------------------------------------------------------------- Date: 8 Jan 90 05:38:38 GMT From: mnetor!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Simpler space suits? In article <15071@bfmny0.UU.NET> tneff@bfmny0.UU.NET (Tom Neff) writes: >What about the other extreme -- capacious balloon or rigid suits >within which the astronaut can move freely. (To scratch, adjust >controls, go #1m or #1f or #2 etc.) ... The real problem is arms and legs, and they are just too useful to replace with something mechanical. -- 1972: Saturn V #15 flight-ready| Henry Spencer at U of Toronto Zoology 1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 8 Jan 90 15:50:31 GMT From: crdgw1!crdos1!davidsen@uunet.uu.net (Wm E Davidsen Jr) Subject: Re: Nuclear Reactors in Space An interesting question: where other than earth would we find radioactives to manufacture RTGs in space (or at least off planet)? Anyone have a good reason to point out some locations as (a) probable to useful isotopes, and (b) of the set of places which are likely to have anything useful how many are accessable using near term (0-20 years) technology? -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "The world is filled with fools. They blindly follow their so-called 'reason' in the face of the church and common sense. Any fool can see that the world is flat!" - anon ------------------------------ Date: 8 Jan 90 15:42:47 GMT From: crdgw1!crdos1!davidsen@uunet.uu.net (Wm E Davidsen Jr) Subject: Re: Simpler space suits? In article <1990Jan7.231400.21390@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: | The current designs provide considerable protection, with a substantial | outer suit that is basically thermal insulation plus armor. My guess, | made without checking the numbers, is that natural debris is not much | of a concern, but in low orbit the man-made junk is a real issue. I would like more information on this... why is the man made stuff such a problem? Things in the same orbit have the same velocity, or they wouldn't be in the same orbit. Now some stuff may be in an eliptical orbit, and cross the path of the EVA, but is likely to have a fairly small closing speed, since highly eliptical orbits which cross LEO tend to cross the atmosphere, too. Looking at what has been launched in terms of number of items, and the volume of LEO, the term "empty space" still doesn't seem too far wrong. Could someone come up with some explanation of why the man-made junk is an issue (or even confirm my gut feeling that it's not all that bad)? -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "The world is filled with fools. They blindly follow their so-called 'reason' in the face of the church and common sense. Any fool can see that the world is flat!" - anon ------------------------------ Date: 8 Jan 90 12:08:20 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Subject: Re: Nuclear Reactors in Space In article <9549@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >I don't agree. The energy requirements were not so much more exacting >than those of Galileo. If we had sunk one-tenth the money into >light-weight electrical batteries that we have sunk into fission and >fusion research, space vehicles would be able to generate all the power >they would need for outer-solar-system missions while still in the >inner system and store it. But propagandizing for "our friend the >atom" has always been a far higher government priority than research >for actual social benefit. Your ignorance is showing again, Tim. The energy demands of a Galileo far exceed what could be stored chemically in a battery of acceptable mass, even in theory. But then what do the hard facts matter when we're cooking up conspiracy theories? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 8 Jan 90 15:43:06 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Nuclear Reactors in Space In article <5939@cps3xx.UUCP> conklin@frith.UUCP (Terry Conklin) writes: >There's _no_ way solar cells could generate that kind of power. In the >same vein, nuclear power will remain strong and reliable regardless of >distance from the sun. Well, reactors don't care how far from the sun they are per se (as long as you don't get too close!), but they do need fuel, and when that runs out you have a lot of complicated hardware doing nothing. Solar arrays diminish in effectiveness as distance from the sun increases, but while they are effective at all they are just about *permanently* effective. And simple, where reactors are complex. Radioisotope thermal generators (RTGs) have the virtue of simplicity but they DO run down -- they are in effect a kind of nuclear 'battery' discharging over the decades. Full blown reactors present many more points of failure -- public safety aside. -- "NASA Awards Acronym Generation :(%( : Tom Neff System (AGS) Contract For Space : )%): tneff%bfmny@UUNET.UU.NET Station Freedom" - release 1989-9891 :(%( : ...!uunet!bfmny0!tneff ------------------------------ Date: 8 Jan 90 05:57:18 GMT From: mnetor!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Nuclear Reactors in Space In article <9547@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >>It sounds like "The Nation" has made a mistake common among the ignorant >>and prejudiced: confusing RTGs and reactors. They are completely different. > >No, they consistently use the phrase "generators". If there is an >error, it's mine. And yours; there are obvious similarities between >conventional reactors and RTGs. "Completely different"? Sure, sure. Completely different is what I said and what I meant. I'd be interested to hear your explanations of those obvious similarities. I'd also be interested to hear either your explanation or "The Nation"'s of how RTGs -- good for hundreds of watts, kilowatts if pushed -- are of vital importance to SDI, which really wants megawatts. Oh, there are incidental support functions that could benefit from them, but again, radical new designs are not needed. Anyone claiming that NASA is finding "excuses" for launching hardware for SDI should first explain why decade-old RTG designs, good for a few hundred watts, considered sufficiently low-risk to be used on a high-profile no-backup planetary mission, somehow are advanced technology that has to be tested in space with elaborate subterfuges. It makes absolutely no sense to me. I would really like to see an *explanation* of this. >>Incidentally, most current work on concentrator-equipped solar arrays is >>being done by the military. > >Ever hear the phrase "co-opt", Spencer? Of course they'd grab control >of the project if they want to suppress it... Tim, Tim, Tim. The big reason they're working on concentrator arrays is simply that they're afraid they won't be allowed to launch nuclear power systems. There is no need to invoke sinister ulterior motives. They didn't "grab control" of the "project"; there was no project until they started several. >The fact is, by NASA's own >studies, we'd have the technology now if it had been funded... There are many useful technologies that we would probably have if they had been funded. There has been a serious dearth of civilian technology funding. >But >somehow, with the military in charge of the research, nothing seems to >be getting done. I see things being done, actually, albeit slowly. One reason why things are a bit slow is that the military has a bunch of extra objectives for the systems, like anti-laser hardening. They also aren't even slightly interested in low-light-level systems for planetary missions, which is why you don't see NASA eagerly adopting their systems for future missions. Even within the mission types they are interested in, they're not exactly funding things abundantly -- concentrator solar systems are a possible long-term enhancement for next-generation routine military programs, plus a low-priority backup for SDI's nuclear sources (which are not getting exactly tremendous funding themselves). There are perfectly mundane reasons why simply isn't much money or priority going into them. -- 1972: Saturn V #15 flight-ready| Henry Spencer at U of Toronto Zoology 1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 8 Jan 90 07:24:56 GMT From: ucsdhub!celit!dave@ucsd.edu (Dave Smith) Subject: Re: Nuclear Reactors in Space In article <9547@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >In article <9537@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >>>... But then the military wouldn't have any excuse to go testing >>>RTG's in space, and this vital component of SDI technology would >>>languish. > >In article <1990Jan7.214747.19787@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) >writes: >>It sounds like "The Nation" has made a mistake common among the ignorant >>and prejudiced: confusing RTGs and reactors. They are completely different. > >No, they consistently use the phrase "generators". If there is an >error, it's mine. And yours; there are obvious similarities between >conventional reactors and RTGs. "Completely different"? Sure, sure. > >As for your personal attacks, a hearty fuck you in return. > Tim, please go back to sf-lovers where you are at least expected, if not well loved. (This is a personal attack. I didn't see any of these in Henry's posting). Henry made the good point that SDI requires power outputs far in excess of that supplied by RTG's, ergo SDI isn't driving RTG development. Yes, there are obvious similarities between RTG's and reactors. They both send people running in circles screaming "Nuclear! Nuclear!". They're also both chock-full of nasty radioactive thingies, but other than that, not a whole lot of similarities. -- David L. Smith FPS Computing, San Diego ucsd!celerity!dave or dave@fps.com "I'm trying to think, but nothing happens!" - Curly Howard ------------------------------ Date: 8 Jan 90 20:22:23 GMT From: vsi1!v7fs1!mvp@apple.com (Mike Van Pelt) Subject: Re: Nuclear Reactors in Space In article <1990Jan8.151837.6831@utzoo.uucp> kcarroll@utzoo.uucp (Kieran A. Carroll) writes: >A question: if it turns out to be impossible to produce batteries >significantly better than those currently available, would >[Tim Maroney] still object to the use of RTGs on spacecraft? Ha! You've gotta be kidding. RTG's are NOOOKLIER, made of ATOMS just like ATOMIC BOMBS. It's an unfortunate fact of life that there are a number of people out there who react to any mention of the "N-word" with mindless, unreasoning, superstitious dread, and no arguments, no matter how well reasoned and firmly based in fact, will sway them in the slightest. (I have heard some reasoned, though, in my opinion, quite mistaken arguments against nuclear power. Tim's wild-eyed paraoid rantings against anything containing the "N-word" are not among them.) -- Mike Van Pelt | What happens if a big asteroid hits Earth? Headland Technology | Judging from realistic simulations involving a (was: Video Seven) | sledge hammer and a common laboratory frog, we ...ames!vsi1!v7fs1!mvp | can assume it will be pretty bad. -- Dave Barry ------------------------------ Date: 9 Jan 90 01:36:36 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Subject: Re: Nuclear Reactors in Space In article <1990Jan8.055718.27937@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >Incidentally, most current work on concentrator-equipped solar arrays is >being done by the military. Some interesting work on an exciting new kind of concentrator cell by Boeing is described in IEEE AES Magazine, Nov. 1989, pages 3-9. As far as I can tell, it's internally funded, although Entech (who provided the prismatic covers) receives NASA and SDIO funding. These are those 31% (AM0) / 37% (AM1.5) GaAs/GaSb stack cells that promise to shrink the size of space solar arrays by 50%. In all this talk of nuclear vs. solar arrays for outer planetary missions, another possibility hasn't been mentioned. A spacecraft in orbit around Jupiter is moving rapidly through a strong magnetic field. It should be possible to generate power with an electrodynamic tether, especially when very near the planet. Now, this will slow the spacecraft, but the available kinetic energy is very large (Jupiter has a very deep gravity well), and the orbit could be pumped up again by slingshoting off Jupiter's moons. I doubt this would have been feasible for Galileo, but it is an interesting possibility for future Jupiter probes. It would let you, for example, place a spacecraft into low circular orbit (not possible with ordinary chemical rockets without aerobraking), and would give that LJO spacecraft a lot of power to play with (maybe for radar observations of Jupiter's atmosphere?). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 9 Jan 90 00:56:42 GMT From: calvin.spp.cornell.edu!johns@cu-arpa.cs.cornell.edu (John Sahr) Subject: Re: Simpler space suits? In article <1990Jan8.053838.27138@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <15071@bfmny0.UU.NET> tneff@bfmny0.UU.NET (Tom Neff) writes: >>What about the other extreme -- capacious balloon or rigid suits >>within which the astronaut can move freely. (To scratch, adjust >>controls, go #1m or #1f or #2 etc.) ... > >The real problem is arms and legs, and they are just too useful to >replace with something mechanical. One does not obviously preclude the other. It is not clear to me why a suit must be strictly anthropomorphic. Why not have a suit which is more like a walking glovebox rather than a walking glove? In other words, allow considerable internal room, enough so that the human could completely retract his or her arms, allowing among other things internal comfort, eating, scratching, as well as more than two arms (special purpose arms, for example). This would be unwieldy on planets with gravity approaching Earth's, of course. But how about the moon? And how about free fall? -- John Sahr, | Electrical Engineering - Space Plasma Physics johns@alfven.spp.cornell.edu | Cornell University, Ithaca, NY 14853 ------------------------------ Date: 9 Jan 90 02:37:22 GMT From: moonzappa!loren@lll-winken.llnl.gov (Loren Petrich) Subject: Re: Nuclear Reactors in Space In article <9537@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >Those interested in the subject should be sure to read the November 20 >editorial in "The Nation" documenting the fact that NASA's own studies >have shown that concentrated solar array technology would have worked >as well as nuclear reactor technology, as well as the followup in the >letters column in the current (January 8/15) issue. > It really must be said that some space missions would be difficult or impossible without nuclear power. Consider those infamous RTG's. Without them, no missions to the outer solar system would have been possible. Sunlight just gets TOO diluted out there. Currently, the Pioneer and Voyager craft are being tracked for as long as one can get a signal from them, which will be (if all goes well) at least the next couple of decades. These craft send direct information of the solar wind (from where they are at), and if we are lucky, they may cross the "heliopause" (where the solar wind stops) and provide our first direct probe of the interstellar medium. These craft are also affected by the gravity of solar-system objects, and they will certainly be affected by any solar-system mass outside of Neptune's orbit, such as the Oort cloud of comets. So one should not complain too loudly about RTG's and the like. There are some other nice features about RTG's. They have no moving parts, they are always "on", and they are invulnerable to radiation damage. The same cannot be said about solar panels, which are degraded by strong radiation, and which must always be pointed towards the Sun. Though nuclear reactors may have some mechanical reliability problems, connected with moving control rods and pumping coolant, they share with RTG's of not needing to be pointed at the Sun. I wonder if anyone has evaluated any solar power source that is radiation-proof, such as some thermal cycle? How much progress has been made in attempting to make photovoltaic cells resistant to radiation degradation? I have a feeling that the likes of the Christic Institute enjoy tying up big organizations like NASA with lawsuits, and that's why they do stuff like that. ^ Loren Petrich, the Master Blaster \ ^ / loren@moonzappa.llnl.gov \ ^ / One may need to route through any of: \^/ sunlight.llnl.gov <<<<<<<<+>>>>>>>> lll-lcc.llnl.gov /v\ lll-crg.llnl.gov / v \ star.stanford.edu / v \ v "What do you MEAN it's not in the computer?!?" -- Madonna ------------------------------ End of SPACE Digest V10 #401 *******************