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, 30 Jun 91 05:19:31 -0400 (EDT) Message-ID: <0cPO8Pi00WBwM2S05v@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sun, 30 Jun 91 05:19:24 -0400 (EDT) Subject: SPACE Digest V13 #753 SPACE Digest Volume 13 : Issue 753 Today's Topics: Re: == No Subject == == No Subject == Re: Dark matter Space electronics Re: Platinum-group metal concentrations in earth-crossing objects microsat tracking The other side of the sun Re: Microgravity? Solar sails and Belt mining Re: Solar sails and Belt mining Re: == No Subject == Mining El Dorado help on Henyey_Greenstein phase function ? 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: 16 Jun 91 17:44:16 GMT From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu!palmer@ucbvax.Berkeley.EDU (David Palmer) Subject: Re: == No Subject == shafer@skipper.dfrf.nasa.gov (Mary Shafer) writes: >You're quite incorrect. I asked Gordon Fullerton (you know, STS-2, etc) >about this and he said that the Great Wall isn't even visible in LEO. >However, quite a few man-made structures are visible from LEO, including >dams, airports, freeways in the deserts, and cities. >Dave Scott (Apollo 15) once told me that the only man-made thing he >could see from the moon was city lights at night and even those were >pretty dim. Probably the easiest manmade thing to see from space is the Sahara Desert. (This desert is the result of domestic animals under human control, e.g. goats, eating away the vegetation at the periphery, allowing the desert to spread.) -- David Palmer palmer@gap.cco.caltech.edu ...rutgers!cit-vax!gap.cco.caltech.edu!palmer "Operator, get me the number for 911" --Homer Simpson ------------------------------ Date: 16 Jun 91 12:59:22 GMT From: mcsun!ukc!slxsys!ibmpcug!demon!news@uunet.uu.net (Ian Stirling) Subject: == No Subject == #In article <2955@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: # ##The only manmade structure that can be seen with the naked eye from space, ##the Great Wall of China, has been around for a fair amount of time in #....... # >BZZZT...Wrong. TONS of stuff is visible from LEO. Do you think that >Manhattan or LA suddenly become invisible because you are 120 miles >up? Perhaps the Great Wall is the only object visible from the Moon or >somesuch distance. > BZZZZZT,BZZZZZZT WRONG WRONG WRONG. 8^) The Great Wall of China is the only thing visible from space with "the naked eye." Steve ___________________________________________ kuwait? Mail to either |PLEASE do not send large Printf%cix@ukc.ac.uk |(>20K)mail messages as Printf@cix.compulink.co |I get charged for them. Printf@cix.uucp | one of these may work | ------------------------------ Date: 17 Jun 91 01:59:31 GMT From: att!cbfsb!cbnewsb.cb.att.com!wa2ise@ucbvax.Berkeley.EDU (robert.f.casey) Subject: Re: Dark matter This thought crosses my mind on the topic of dark matter: There can't be much of any sort that we are not familiar with in the solar system. Or else the laws of Gravitation that Newton discovered would be confused. If the solar system was imbedded in a sea of unusual dark matter, calculations on the interactions between planets wouldn't work out right. Maybe further out there is some dark matter to explain the deviations of Neptune that prompted the search that found Pluto. There can't be much in the inner solar system, or else our space probes, satellites and moons would travel on paths that wern't correctly predicted. Any of you rocket scientists in the know have comments? ------------------------------ Date: Sun, 16 Jun 91 09:36 EDT From: M_HAYDEN%GBURG.BITNET@vma.cc.cmu.edu Subject: Space electronics X-Envelope-To: space+@andrew.cmu.edu I'm interested in the technical details of various space craft sensors and electronics. Are the schematics and circuit details of the electronics available? I'm curious how the particle sensors and various field detectors operate. Can anybody point me to a good reference? Michael B. Hayden m_hayden@gburg.bitnet m_hayden@gettysburg.edu ------------------------------ Date: 16 Jun 91 23:41:10 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!wuarchive!cs.utexas.edu!ut-emx!nowhere!sking@ucbvax.Berkeley.EDU (Steven King) Subject: Re: Platinum-group metal concentrations in earth-crossing objects Of course, all of this presumes that even if you were to get there and the processes were viable, that the asteriod is yours to mine. International law, as I understand it, is less than clear on this issue. A few billion in precious metals might buy a lot of influence, but it would also buy a lot of envy. -- If it don't stick, stink, or sting It ain't from Texas. ..!cs.utexas.edu!ut-emx!nowhere!sking ------------------------------ Date: 16 Jun 91 12:59:26 GMT From: mcsun!ukc!slxsys!ibmpcug!demon!news@uunet.uu.net (Ian Stirling) Subject: microsat tracking >>retrofitting standard,$5,000 satellite dishes.Can somebody comment >>on what it takes to get a standard TV satellite dish to track a >>low-earth-orbiting satellite? > >Basically a new mount and more powerful motors and realtime tracking >software running on a personal computer. The polar mount used >on home dishes gives limited continous sky coverage in a tracking Why would it need more powerful motors? Arn't most mounts designed for reasonably rapid change between different satelites ,surely all that would be needed is a cleverer or re-programmed driver? Mail to either |PLEASE do not send large Printf%cix@ukc.ac.uk |(>20K)mail messages as Printf@cix.compulink.co |I get charged for them. Printf@cix.uucp | one of these may work | ------------------------------ Date: 16 Jun 91 19:12:37 GMT From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!hellgate.utah.edu!csn!scicom!wats@ucbvax.Berkeley.EDU (Bruce Watson) Subject: The other side of the sun Is there a spacecraft out there on the other side of the sun from us that could tell if there are any large spots like the one now just rotating off the face? -- | | One hundred thousand people is the optimum | | wats@scicom | population for a world in which the work will be | | | done by robots. -- Arthur C. Clarke | ------------------------------ Date: 14 Jun 91 21:59:21 GMT From: aio!ecfa!matthews@eos.arc.nasa.gov (Michael C. Matthews) Subject: Re: Microgravity? In article <1991Jun07.104427.1061@disk.uucp> joefish@disk.uucp (joefish) writes: > >After visiting the 500 foot vacuum zero gravity at NASA Lewis >Research Center in Cleveland in 1968, I found several facts >very interesting. > >The drop time is about 5 seconds, but they have a spring loaded >slingshot that throws the package up to the top, giving about >10 seconds total zero (near zero) gravity. This facility >... >Joe Fischer uunet!coplex!disk!joefish Darn! He gave it away! And I thought I was gonna make a bundle going around to all those drop facilities as a consultant, telling them how they can cheaply double their microgravity time... :-) -- Mike Matthews | matthews%ecfa@jesnic.jsc.nasa.gov Tethered Vehicle Analysis Group | (backup) --> matthews@asd2.jsc.nasa.gov Advanced Projects Section; Navigation, Control, and Aeronautics Department Lockheed Engineering & Sciences Company, Houston, Texas, (713) 333-7079 ------------------------------ Date: 16 Jun 91 12:59:17 GMT From: mcsun!ukc!slxsys!ibmpcug!demon!news@uunet.uu.net (Ian Stirling) Subject: Solar sails and Belt mining If you can make a workable solar sail how much more difficult is it to make a large parabolic mirror for melting large boulder size chunks of rock? Could you mine a asteroid my melting it and allowing the vapour that comes off to condense on nearby cooled surfaces,using a sort of fractional distilation to seperate the metals.Also could you get higher temperatures than the surface of the sun by filtering the incoming light at the mirror(diffraction grating ?)to leave only the higher energy photons,this does not seem to violate any laws as you are only able to use a small fraction of the incoming light to heat the object but most of the light goes past at lower overall energy. Mail to either |PLEASE do not send large Printf%cix@ukc.ac.uk |(>20K)mail messages as Printf@cix.compulink.co |I get charged for them. Printf@cix.uucp | one of these may work | ------------------------------ Date: 16 Jun 91 00:19:01 GMT From: van-bc!rsoft!mindlink!a684@ucbvax.Berkeley.EDU (Nick Janow) Subject: Re: Solar sails and Belt mining Non-imaging optics could also improve the thermal efficiency of generators. They could possibly turn a working fluid into plasma, driving an MHD generator. This needs a fair bit of work in developing large-scale non-imaging optics and in developing thermal radiators for use in space (though the techniques should work here just as well). I wonder how such a system would compare with other solar generation schemes. -- Nick_Janow@mindlink.bc.ca ------------------------------ Date: 16 Jun 91 16:50:27 GMT From: swrinde!elroy.jpl.nasa.gov!news.arc.nasa.gov!skipper!shafer@ucsd.edu (Mary Shafer) Subject: Re: == No Subject == In article <1991Jun16.125922.7401@demon.co.uk> printf@cix.compulink.co.uk (Ian Stirling) writes: #In article <2955@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: # ##The only manmade structure that can be seen with the naked eye from space, ##the Great Wall of China, has been around for a fair amount of time in #....... # >BZZZT...Wrong. TONS of stuff is visible from LEO. Do you think that >Manhattan or LA suddenly become invisible because you are 120 miles >up? Perhaps the Great Wall is the only object visible from the Moon or >somesuch distance. > BZZZZZT,BZZZZZZT WRONG WRONG WRONG. 8^) The Great Wall of China is the only thing visible from space with "the naked eye." You're quite incorrect. I asked Gordon Fullerton (you know, STS-2, etc) about this and he said that the Great Wall isn't even visible in LEO. However, quite a few man-made structures are visible from LEO, including dams, airports, freeways in the deserts, and cities. Dave Scott (Apollo 15) once told me that the only man-made thing he could see from the moon was city lights at night and even those were pretty dim. I've been to the Great Wall and it's not very big, it's tan, and the chaparrel grows right up to it. I think you'd be hard-pressed to see it from 40,000 ft, let alone LEO. -- Mary Shafer shafer@skipper.dfrf.nasa.gov ames!skipper.dfrf.nasa.gov!shafer NASA Ames Dryden Flight Research Facility, Edwards, CA Of course I don't speak for NASA "Turn to kill, not to engage." CDR Willie Driscoll ------------------------------ Date: 16 Jun 91 19:51:53 GMT From: bu.edu!rpi!usc!srhqla!denwa!stb!charles@bloom-beacon.mit.edu (Charles (from bbs)) Subject: Mining El Dorado How do we mine the El Dorado asteroid ? Is it one big stainless steel nugget, or is it differentiated ? Either way, I propose blasting it to pieces using high explosives. If it is a homogeneous stainless steel nugget I would drill a hole right to the center and insert a small nuclear device. If it is differentiated, conventional explosives might suffice. Nuclear gives more bang per pound, so better than chemical and takes less propellant to send it to El Dorado. We do not want lots of fragments flying everywhere, all we need is to create a powerful shock wave to disrupt the asteroid structure. The shock should be small enough that gravity will continue to hold the pieces together. We could literally surround the asteroid with a safety net to ensure most of it is retained. Once shocked the pieces can be individually transported or processed by a robot smelter. If it is well differentiated it might be possible to visually separate out nuggetts of rare metals, and discard the silicates and iron. A weak acid could dissolve reactive metals ( alkali earth and alkali metals and iron ) and heavier metals like Gold and Platinum would be beneficiated. If desired the acid solution could be electrolysed with low energy to recover the lighter metals. Beneficiating by weight might be possible, would have to spin the nuggetts in a centrifuge to find out how dense they are. Each nugget could also be scanned by alpha particle back scattering or other radio-spectroscopy means, and then sorted into valuable and less valuable bins. Probably cheaper than electrolysis too. Most efficient might be to use minimum size ( ie critical mass only ) nuclear charges, and progressively shock parts of El Dorado, that allows more margin for error in case we guess wrong about the quantity of shock needed - do not want to over do it ! Would need rather a lot of diamond drills if it is steel, maybe somebody could design a laser cutting torch so we can burn our way in. How about a deliberate nuclear pile meltdown on the surface, the hot pile melts to the center via gravity - al la China Syndrome. An advantage of a single blast dead center would be that the surface structure would be least affected, so it might be possible to the centre, and leaving a large hollow structure which could be turned into a human habitat. I like that better than progressively blasting it completely to pieces from the outside. Residual radiation might be a problem for future colonists, I wonder what the half-life would be. In the immediate term it would be interesting to send a probe to El Dorado, to see if it is differentiated or homogoneous. El Dorado is probably spinning, so the blast could be timed such that the exhaust coming out of the drill hole would cause a reaction which would tend to propel the asteroid towards the Earth a little. We do not have controlled fusion, but maybe a large thermonuclear device could be designed as a shaped charge. After the initial fission explosion and hollowing out some of the interior, the thermonuclear shaped charge could be inserted into the interior of El Dorado, and the drill hole widened. The blast would then be mostly directed out through the vent hole, creating a more substantial thrust reaction, which could maybe manouver El Dorado within a few million miles of Earth. This would be most useful if the blast could be done at perihelion, thus lowering the aphelion, making collection of the asteroid pieces much cheaper. Perhaps the nuclear shocking and thrusting could be a government program. Then collection and benefaction of the pieces could be by private prospectors. * Origin: Ventura Co NSS 805-649-5314 STS final approach (1:206/2403.0) ------------------------------ Date: 16 Jun 91 08:37:22 GMT From: agate!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!munnari.oz.au!uniwa!cc.curtin.edu.au!smathahap@ucbvax.Berkeley.EDU Subject: help on Henyey_Greenstein phase function ? I am working on atmospheric correction of NDVI. I need some help about the appropriate values of rural aerosol Henyey-Greenstein phase function asymmetry parameters to use in my work. The only values I am able to find are for marine aerosol. I will be very pleased for your help. Paul Mathaha Curtin University of Technology, Physics Department, GPO Box U1987 Perth, W.A. 6001 ------------------------------ End of SPACE Digest V13 #753 *******************