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 ; Sat, 4 Nov 89 03:29:43 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 4 Nov 89 03:28:58 -0500 (EST) Subject: SPACE Digest V10 #204 SPACE Digest Volume 10 : Issue 204 Today's Topics: Re: PowerSat Options Re: Manned Jupiter Mission Re: Moon Colonies / Ant Tanks? Re: Moon Colonies / Ant Tanks? Re: PowerSat Options NASA appoints Spacelab Payload Specialists (Forwarded) Boeing 37% efficient PV cell trajectory of Voyager II Re: Payload Canister Investigation Update (Forwarded) Re: Manned Jupiter Mission Voyager/Galileo Camera function ---------------------------------------------------------------------- Date: 3 Nov 89 17:25:01 GMT From: crdgw1!crdos1!davidsen@uunet.uu.net (Wm E Davidsen Jr) Subject: Re: PowerSat Options In article <1989Nov2.140102.2133@cs.rochester.edu>, dietz@cs.rochester.edu (Paul Dietz) writes: | Jeez. The microwave beam has low power density because it is | diffraction limited (if it wasn't, we've made the transmitter too | big). You want a failsafe system to guarantee the laws of physics are | not violated? As I have mentioned before, the twit on the street doesn't care about the laws of physics, he doesn't want to have anything which sounds like atomic, nuclear, or radiation. That why the NMR system was a flop, and MRI is great. Same device, but "Nuclear Magnetic Resonance" is *scarey* and "Magnetic Resonance Imaging" isn't. People really had exploratory surgery because they were afraid of it. Now if you tell him that you are going to put a microwave in the sky, and it's "two million time more powerful than your home microwave oven," and that it's safe by the laws of physics... I would rather add a percent to the cost and be sure that the beam can never be pointed at a populated area, than to try and convince people that it won't hurt. For that matter, if you told me twenty years ago that EMF from 60 cycle current could cause cancer and birth defects I would have laughed in your face. Now that evidence of higher birth defect rates near power lines is showing up, I'm not so sure that I know all the answers. And DC incubators produce fewer defective chickens than AC... and they have less cancer as they mature. So based on the public relations thing and the possibility of low incidence medical effects, I would certainly be more comfortable if the security were designed in from the start than legislated in later. -- 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: 3 Nov 89 22:15:28 GMT From: ncrlnk!ncrcce!ncrons!johnson@uunet.uu.net (Wayne D. Johnson) Subject: Re: Manned Jupiter Mission > Things that make 2 T fields in people sized >volumes are large and heavy. You might be better off turning the darn >magnet off and re-casting it into a shield. Save on the electric bill, too. How about a permenent magnet? -- Wayne Johnson (Voice) 612-638-7665 NCR Comten, Inc. (E-MAIL) W.Johnson@StPaul.NCR.COM or Roseville MN 55113 johnson@c10sd1.StPaul.NCR.COM These opinions (or spelling) do not necessarily reflect those of NCR Comten. ------------------------------ Date: 4 Nov 89 03:09:24 GMT From: munnari.oz.au!bruce!monu1!vaxc!cen466p@uunet.uu.net Subject: Re: Moon Colonies / Ant Tanks? In article <9987@attctc.Dallas.TX.US>, ltf@attctc.Dallas.TX.US questions >How deep would you have to dig to get 1/6th earth gravity? :-) From what I learnt from school, I recall that the gravitational force is inversely proportional to the distance between the center of masses. Hence the gravitational force will increase as you go towards the center of the earth. ---------------------------------------------------------------------------- "Absence of Evidence does not necessarily mean Evidence of Absence" + - + - + - + - + - + UUCP: ... murtoa.cs.mu.oz.au!munnari.oz.au!bruce!monu1!vaxc!partha CSNET: partha@vaxc.cc.monash.edu.au (or) cen466p@vaxc.cc.monash.edu.au ------------------------------ Date: 3 Nov 89 21:00:39 GMT From: cs.utexas.edu!ut-emx!walt.cc.utexas.edu!wastoid@tut.cis.ohio-state.edu (Feulner ... Matthew Feulner) Subject: Re: Moon Colonies / Ant Tanks? In article <9987@attctc.Dallas.TX.US> ltf@attctc.Dallas.TX.US (Lance Franklin) writes: > >How deep would you have to dig to get 1/6th earth gravity? :-) > >Lance > Pretty deep, actually about (6378-1700) km deep. It would probably cost more to go down that far than to the moon. Although to get 0g, you just have to go to LEO, which is cheaper still. Matt ------------------------------ Date: 3 Nov 89 22:00:31 GMT From: rochester!yamauchi@pt.cs.cmu.edu (Brian Yamauchi) Subject: Re: PowerSat Options In article <1545@crdos1.crd.ge.COM> davidsen@crdos1.UUCP (bill davidsen) writes: >In article <1989Nov2.140102.2133@cs.rochester.edu>, dietz@cs.rochester.edu (Paul Dietz) writes: > >| Jeez. The microwave beam has low power density because it is >| diffraction limited (if it wasn't, we've made the transmitter too >| big). You want a failsafe system to guarantee the laws of physics are >| not violated? > > As I have mentioned before, the twit on the street doesn't care about >the laws of physics, he doesn't want to have anything which sounds like >atomic, nuclear, or radiation. That why the NMR system was a flop, and >MRI is great. Same device, but "Nuclear Magnetic Resonance" is *scarey* >and "Magnetic Resonance Imaging" isn't. People really had exploratory >surgery because they were afraid of it. > > Now if you tell him that you are going to put a microwave in the sky, >and it's "two million time more powerful than your home microwave oven," >and that it's safe by the laws of physics... Actually, the NMR/MRI example suggests a solution. Don't call it a microwave beam, call it Reduced Frequency Sunlight. :-) _______________________________________________________________________________ Brian Yamauchi University of Rochester yamauchi@cs.rochester.edu Computer Science Department _______________________________________________________________________________ ------------------------------ Date: 4 Nov 89 01:50:59 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: NASA appoints Spacelab Payload Specialists (Forwarded) The following release is a corrected version of HQ 89-169, NASA Appoints Spacelab Payload Specialists, issued yesterday. Please substitute the corrected version for any copies of the original release. Thanks. Paula Cleggett-Haleim Headquarters, Washington, D.C. RELEASE: 89-169A NASA APPOINTS SPACELAB PAYLOAD SPECIALISTS Dr. Lennard A. Fisk, NASA's Associate Administrator for Space Science and Applications, recently appointed two Spacelab payload specialists to participate in Spacelab missions to be flown aboard the Space Shuttle. Dr. Millie Hughes-Fulford will be a prime payload specialist for Spacelab Life Sciences-1 (SLS- 1) and Dr. Stanley N. Koszelak will serve as the U.S. backup payload specialist for Spacelab-J. Hughes-Fulford, 43, previously assigned to Spacelab Life Sciences-2 as the prime payload specialist, has been reassigned to SLS-1 to replace Dr. Robert W. Phillips, 60. Phillips is stepping down for medical reasons. He will continue his duties as an SLS-1 mission support team member. Hughes-Fulford is an associate professor of biochemistry at the University of California Medical Center, San Francisco, and a medical researcher at the Veterans Administration Medical Center in San Francisco. SLS-1 is the first mission to use Spacelab, a laboratory that fits in the Space Shuttle cargo bay, as a dedicated biological research facility. The 20 scientific investigations onboard will help answer critical questions about the way humans adapt to microgravity and readapt to Earth's gravity. Koszelak, 36, is an assistant research biochemist at the University of California at Riverside. As the U.S. backup payload specialist for Spacelab-J, Koszelak will perform critical ground support duties during the mission. Spacelab-J is jointly sponsored by NASA and the National Space Development Agency of Japan. A Japanese payload specialist also will fly on Spacelab-J. SLS-1 is scheduled to fly in August 1990 aboard Space Shuttle orbiter Columbia and is managed by the Johnson Space Center, Houston, for NASA's Office of Space Science and Applications (OSSA), Washington, D.C. Spacelab-J, scheduled to fly in June 1991, is managed by the Marshall Space Flight Center, Huntsville, Ala., for NASA's OSSA. ------------------------------ Date: 3 Nov 89 20:35:50 GMT From: rochester!dietz@pt.cs.cmu.edu (Paul Dietz) Subject: Boeing 37% efficient PV cell In article <4421@cs.yale.edu> sanders-malcolm@CS.YALE.EDU (SANDERS-MALCOLM) writes: >Cheap is an understatement if your numbers are correct here! [ calculation of $2.75/kW ] >This price is about a factor of 1000 less than what is commonly >held to be the ballpark figure for the breakeven price at which >PV power becomes competitive with conventional sources. You made an arithmetic error. For a 25 cm concentrator focusing light onto a 2.5 cm cell, I get about $.27 per watt, or $275 per kilowatt. It's still impressive, if true. This figure does not include trackers, but the high efficiency would be very helpful there. Here's a more complete description of the cells... --- The Oct. 23 issue of Aviation Week and Space Technology has an article about a significant advance in photovoltaic technology. Boeing, using only internal funding, has developed a mechanically stacked GaAs/GaSb concentrator cell that achieves 31% efficiency in space (air mass 0) and 37% on Earth (air mass 1.5, I guess). The previous space cell record was 24.1% by Varian Associates. The previous ground record was a bit over 30% using a GaAs/Si tandem cell from Sandia. The GaAs/GaSb stacked cell is about twice as efficient as space PV cells currently in use. The Boeing cell consists of a GaAs top cell with a bandgap of 1.42 eV (.9 microns). It passes infrared light to the bottom GaSb cell, which has a bandgap of .72 eV (1.7 microns). The voltage of the GaSb cell is 1/3 of that of the GaAs cell. Three stacks are arranged so that the GaAs cells are in parallel with each other and with the three GaSb (which are in series). Special care was given to making the GaAs cell transparent to infrared light. Metallization was placed on the front of the top cell, rather than on the back as is usually done. The contacts were in the form of gridlines. A prismatic cover from Entech (Dallas) directed the incoming light into the the gaps between the gridlines. Decreased N-type doping in the GaAs and special antireflection coatings were also used. The two cells in a stack are placed on opposite sides of a hole in a PC card, which is then placed under a plastic Fresnel lens that concentrates sunlight 100 times. The active area of the cells is 2.5 cm in diameter. AW&ST quotes Lewis Fraas, the project manager, as saying that Boeing hopes the cells, which do not requite submicron features, epitaxial layers, or a lot of complexity, could be manufactured for $1 per chip. Fraas says they have a design on paper for a lens/cell/interconnect system that would cost $5 per assembly. The bottom cell is also interesting in "thermo-photovoltaic" systems. Thermal radiation from a red-hot object could be converted by an array of GaSb cells to electricity at > 20% efficiency, vs. perhaps 5% in existing thermoelectric systems. I can imagine this being used for, say, a lunar base, where the heat source is a high temperature nuclear reactor and where conventional heat engines would be too unreliable. Boeing is shifting the emphasis of its project to manufacturing, cost reduction and system design. NASA has expressed interest in using the cells on the space station; some aerospace companies want the cells right away. Fraas says it could be a period of years before the cells are ready to use [in aerospace applications]. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 3 Nov 89 14:33:21 GMT From: mcsun!cernvax!chx400!ethz!keller@uunet.uu.net (Christoph Keller) Subject: trajectory of Voyager II Hi space freeks: I am posting for a friend, so please don't reply to me: Does somebody of you have the data describing the trajectory of Voyager II or has any hint on how to get it? Please reply to: nufer@sandoz.ch@cernvax.bitnet or nufer@sandoz.ch Thanks in advance for your assistance. ----------------------------------------------------------------------------- Christoph Keller keller@czheth5a.bitnet Institute of Astronomy ckeller@solar.stanford.edu ETH-Zentrum keller@ifa.ethz.ch CH-8092 Zuerich keller@ethz.uucp Switzerland ----------------------------------------------------------------------------- ------------------------------ Date: 1 Nov 89 15:51:20 GMT From: mcsun!ukc!strath-cs!cs.glasgow.ac.uk!memex!peter@uunet.uu.net (Peter Ilieve) Subject: Re: Payload Canister Investigation Update (Forwarded) In article <34528@ames.arc.nasa.gov> NASA (via Peter E. Yee) writes: > Payload Canister Investigation Board: > > Witness interviews began late Tuesday afternoon and > concluded late Wednesday. > > There are no apparent warps or other defamations of > the doors. ----------- > I know that Americans are fond of litigation, but this is ridiculous. Are NASA's lawyers frightened that the witnesses will say nasty things about the doors? Are they highly strung doors, sensitive about their reputation? :-) Peter Ilieve peter@memex.co.uk Padding While I am padding for inews, thanks to Peter Yee for the NASA stuff. Padding Rhubarb Rhubarb Rhubarb Rhubarb Rhubarb Rhubarb Rhubarb ------------------------------ Date: 3 Nov 89 16:51:12 GMT From: frooz!cfa.HARVARD.EDU@husc6.harvard.edu (Steve Willner) Subject: Re: Manned Jupiter Mission In article <228@cfa.HARVARD.EDU> I wrote: >>A quick calculation for the magnetic field strength necessary gives >>B=mvc/r, where B is magnetic induction ("magnetic field") in gauss, m In article <1442@calvin.EE.CORNELL.EDU>, johns@calvin.EE.CORNELL.EDU (John Sahr) corrected: > So close, and yet so far. This equation would be correct it the proton > charge was included: > > B = mvc/(er) where e = 4.8x10^-10 cgs How embarrassing! He's quite right, of course. Good thing I'm not designing the cosmic ray shields for an actual mission. Think before posting! Think before posting! Think before posting! .... ------------------------------------------------------------------------- Steve Willner Phone 617-495-7123 Bitnet: willner@cfa 60 Garden St. FTS: 830-7123 UUCP: willner@cfa Cambridge, MA 02138 USA Internet: willner@cfa.harvard.edu ------------------------------ Date: 2 Nov 89 19:12:59 GMT From: systech!fjk@uunet.uu.net (Fred Kokaska) Subject: Voyager/Galileo Camera function Can the cameras on the Voyager and Galileo spacecrafts be aimed back at the spacecrafts themselves? Can you imagine a Voyager scrapbook? "Here's me in front of Saturn!" |-) It might also show some of the speculated impact damage. Fred Kokaska | "Remember; Wherever you go - There you are!" uunet!systech!fjk | Buckaroo Bonzai ------------------------------ End of SPACE Digest V10 #204 *******************