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 ; Thu, 2 Nov 89 03:23:23 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Thu, 2 Nov 89 03:23:02 -0500 (EST) Subject: SPACE Digest V10 #187 SPACE Digest Volume 10 : Issue 187 Today's Topics: Manned Jupiter Mission (was Re: Condensed CANOPUS - August 1989) Re: Asteroids as weapons of mass destruction Re: Wood in space Re: PowerSat Options Re: Galileo and the proposed asteroid flybys Voyager update Re: Voyager update Re: PowerSat Options Re: PowerSat Options Launch Advisory: COBE launch delayed (Forwarded) Re: PowerSat Options Re: PowerSat Options ---------------------------------------------------------------------- Date: 29 Oct 89 21:01:52 GMT From: rochester!yamauchi@pt.cs.cmu.edu (Brian Yamauchi) Subject: Manned Jupiter Mission (was Re: Condensed CANOPUS - August 1989) In article <1754@cfa183.cfa250.harvard.edu> willner@cfa250.harvard.edu (Steve Willner) writes: > >NASA AWARDS GRANTS FOR FUTURE EXPLORATION STUDIES - can890801.txt - 8/3/89 > >NASA's Office of Exploration has awarded a series of study contracts >to various organizations to provide NASA with ideas, concepts, >devices, systems, trajectories, operations or implementations which >could be applied to furthering human exploration of the solar system. ^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^ >The 20 winners, selected from 115 proposals submitted in response to >the April 12, 1989, NASA Research Announcement, are located in 12 >different states and come from five industry-related firms, two space >support-related organizations, and 13 universities. I'm curious, do any of these study contracts deal with manned missions to locations other than the Moon or Mars? From a scientific point of view, the Jovian system would seem to offer much more than either the Moon or Mars. Imagine the possibilities for exploring Jupiter, the Galilean moons, the smaller moons, and the ring system. Also, from a political / public relations point-of-view this would be a big win -- images from Io are likely to be much more exciting than images from Mars. Are there any technical obstacles to a Jovian mission other than the longer flight time (requiring more supplies, larger ships, etc.) and the radiation around Jupiter? _______________________________________________________________________________ Brian Yamauchi University of Rochester yamauchi@cs.rochester.edu Computer Science Department _______________________________________________________________________________ ------------------------------ Date: 26 Oct 89 13:56:29 GMT From: uc!nic.MR.NET!thor.acc.stolaf.edu!pederstm@tut.cis.ohio-state.edu (Michael Pederson) Subject: Re: Asteroids as weapons of mass destruction Take a small spacecraft out to about a light-year, aim it at Earth, and fire theengines. When it hits, it should have a velocity close to c and would do a lot of damage. ------------------------------ Date: 27 Oct 89 01:46:51 GMT From: crash!orbit!pnet51!schaper@nosc.mil (S Schaper) Subject: Re: Wood in space There is an article in the current Sci.American on upper atmospher erosion of shuttle heat tiles in loe. , s UUCP: {amdahl!bungia, uunet!rosevax, chinet, killer}!orbit!pnet51!schaper ARPA: crash!orbit!pnet51!schaper@nosc.mil INET: schaper@pnet51.cts.com ------------------------------ Date: 27 Oct 89 19:59:01 GMT From: telesoft!roger@ucsd.edu (Roger Arnold @prodigal) Subject: Re: PowerSat Options tneff@bfmny0.UU.NET (Tom Neff) writes: > The two sexiest powersat approaches I'd heard of [..] were > maser pumping to a ground antenna field and superfuel generation > on-orbit for batch re-entry to earth. [..] I'd be curious to see any references on superfuel generation on-orbit. The best ordinary fule (LH2 + LOX) can't begin to deliver enough energy to get its own mass in water to orbit. (Unless you posit an orbiting skyhook, or som other regenerative mechanism for orbital transport). Fuels that would have enough energy, in principle, like stabilized monatomic hydrogen, are all science fiction, as far as I know. But if anyone has come up with a new wrinkle, I'd certainly like to hear about it. Another interesting possibility for powersats that lies somewhere between reality and science fiction is direct generation and rectification of coherent infrared beams, using micro-rectenna structures. With current etching techniques and the potential speed of GAs switching, this should be possible. I don't know if anybody has actually demonstrated it, as yet. > I remain concerned that regardless of how lily-white the generation > methods, if we keep increasing power generation and consumption on this > ball we'll melt the icecaps and drown in waste heat. > -- > "Take off your engineering hat | "The filter has | Tom Neff > and put on your management hat." | discreting sources." | tneff@bfmny0.UU.NET We have a couple orders of magnitude to go before direct human energy use is a significant factor in the energy balance. Solar input to earth is about 2 E17 watts; total human energy use is < E15 watts. Indirect effects, of course, are much more significant. Increased CO2, burning of the rain forests, etc. Sometime, I'd like to be able to calculate the equivalent energy input increase from buning a gallon of gasoline, or a ton of coal, or whatever. - Roger Arnold ucsd!telesoft!roger ------------------------------ Date: 25 Oct 89 17:27:40 GMT From: palmer@tybalt.caltech.edu (David Palmer) Subject: Re: Galileo and the proposed asteroid flybys In article <10769@csli.Stanford.EDU> jkl@csli.stanford.edu (John Kallen) writes: >Now that Galileo is finally on its way, I start wondering whether the >launch delays the probe suffered affect in any way the planned >asteroid rendezvous (sp?). Or were the rendezvous cancelled totally >as a consequence of the fuel shortage due to inefficient impulse >thrusters? Personally, I would really like to see images of asteroids >larger than Phobos and Deimos. Both asteroid rendezvouses (sp?) (the asteroids are Ida and Gaspara) are still planed, but if the launch had been delayed by an additional day, one would have had to be dropped. The current policy is not to commit to the redezvouses until two weeks after the Venus encounter, at which time the size of a mid-course trajectory correction will depend on the decision. This will allow a margin of safety in case Galileo uses up more propellant than expected. David Palmer palmer@tybalt.caltech.edu ...rutgers!cit-vax!tybalt.caltech.edu!palmer Meanwhile, on eng.string.floss, the waxed vs. unwaxed flamewar continues unabated. ------------------------------ Date: Thu, 26 Oct 89 11:52:37 PDT From: Peter Scott Subject: Voyager update Lines: 101 Extracted from NASA's _Voyager Bulletin_, Mission Status Report No. 97, October 16: MAGNETICALLY, NEPTUNE IS MUCH LIKE URANUS As Voyager 2 closed on Neptune, the bets were that Neptune would have a simple magnetic dipole roughly aligned with the planet's rotational axis and centered within the planet. Six of Voyager's instruments measure fields and particles. The first of these to sense the planet is usually the planetary radio astronomy (PRA) subsystem, which detects planetary radio emissions. These radio signals result from dynamo electrical currents generated deep in a planet's interior and carried to space along the planet's magnetic field lines. Charged particles near the planet arre trapped within an imaginary "cage" formed by the magnetic field lines and are swept along as the planet rotates. All seemed quiet in the fields and particles domain until August 17 (PDT) when the PRA began to detect signals from Neptune. From the intervals between the signals, the PRA team deduced that the rotation rate of the bulk of the planet is about 16 hours -- much shorter than the 18-hour period deduced from tracking cloud features in the atmosphere. The next fields and particles event, the bow shock crossing, occurred on August 24. During interplanetary cruise, the spacecraft is in the solar wind where particles travel at supersonic speed near one million miles per hour. At the bow shock, the solar wind flow is slowed to subsonic speeds, heated, and deflected by interaction with the planet's magnetic field. Prior to crossing the Neptune bow shock approximately 35 Neptunian radii from the planet's center (about 865,000 km or 537,000 mi), measurements by the plasma science instrument indicated that the solar wind temperature was 6,300 kelvins, but the density was only 0.0045 protons per cubic centimeter. Within the magnetosheath, the temperature rose dramatically to about 250,000 K and the density to 0.03 protons per cc. Inbound to Neptune, Voyager 2 was in the magnetosheath for about 25 minutes before crossing the planet's magnetosphere at about 22 Neptunian radii (about 500,000 km or 300,000 mi) from the planet's center. The magnetic field did not behave as expected, nor was it even _where_ it was expected. Expecting a magnetic axis roughly aligned with the rotational axis, the fields and particles investigations were geared for an unusual opportunity to directly detect particles spiraling into Neptune's north polar atmosphere along magnetic field lines as Voyager 2 passed near the planet's north pole. However, Dr. John Belcher, principal investigator for Voyager's plasma science investigation, announced on August 25 that from their data, his team inferred a magnetic dipole tilted 50 degrees from the rotational axis -- surprisingly similar to the 59 degree tilt of Uranus' dipole. (Earth's dipole is titled 11 degrees from the rotational axis.) Rather than the expected crossing near the confluence of the magnetic field lines, Voyager 2's path had carried it for the first time through a relatively high-latitude cusp of a planetary plasma domain and then into a more nearly equatorial region of the magnetosphere, allowing observations within the magnetosphere for about one-and-a-half planetary rotations. In addition, Dr. Norm Ness, principal investigator for the magnetometry investigation, reported that Neptune's field is not a simple dipole. (An example of a simple dipole is a child's bar magnet.) The low-energy charged particle (LECP) investigators, led by Dr. Tom Krimigis, reported sensing a tremendous number of protons, as well as helium, carbon, and hydrogen in Neptune's magnetosphere. The LECP team also reported that in the range from 28,000 to 43,000 electronvolts, they found an increased population of energetic protons inside the orbit of Triton. They measured temperatures about 700 million degrees Celsius (over 1.3 billion degrees Fahrenheit) and a density of 0.00025 per cc. The probable source for these hot plasmas is Neptune's ionosphere. The LECP team also reported that Voyager 2 had passed over a magnetic polar area after all, yielding the first direct detection of auroral zone particles impacting the atmosphere of a nonterrestrial planet. Their initial estimates of the auroral power was greater than 1 million watts (Earth's auroral power, which we see as the Northern or Southern Lights, is about 100 billion watts). Because of the tilt and offset of the magnetic field, Neptunian auroras might be expected to occur near the equator rather than at the poles, but because of the complex structure of the magnetic field near the planet, auroral activity is probably widespread. In summary, the quick-look analysis of Voyager's pass through Neptune's magnetosphere indicates that Neptune looks very much like Uranus, magnetically. The dipole is tilted 50 degrees from the rotational axis, and magnetic north is in the southern hemisphere. In addition, the magnetic pole is offset by 2/5 (0.4) of Neptune's radius (Uranus's magnetic pole is offset by 1/3 [0.3] Uranian radius.) The magnetosphere undergoes dramatic changes as the planet rotates and the moons orbit. The dipole moment (the mean field strength at the 1-bar pressure level) is 0.13 gauss R_N^3, but because of the large offset the strength of the field ranges from 1.2 to 0.06 Gauss (Earth's surface field is about 0.3 Gauss). The large variation in field intensities indicates that dynamo electrical currents may be much closer to the "surface" (the 1-bar pressure level) of Neptune than was true for Jupiter or Saturn. In terms of the density of charged particles in the planet's magnetosphere, Voyager's magnetosphere is the emptiest encountered by Voyager. The large tilt and offset apparently allow the satellites and ring particles to effectively "sweep" charged particles out of the magnetosphere. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 26 Oct 89 22:33:14 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Voyager update >Extracted from NASA's _Voyager Bulletin_, Mission Status Report No. 97, >October 16: > >MAGNETICALLY, NEPTUNE IS MUCH LIKE URANUS Speak for yourself, buddy! :-) -- "My God, Thiokol, when do you \\ Tom Neff want me to launch? Next April?" \\ tneff@bfmny0.UU.NET ------------------------------ Date: 25 Oct 89 19:04:00 GMT From: pur-phy!tippy!fireman@ee.ecn.purdue.edu Subject: Re: PowerSat Options There was an excellent report given at the Midwest Space Development Conference here at Purdue last weekend about the Japanese space program, and one the topics was an experiment on transmitting power via microwaves... The problems are keeping the beam focused at the right spot, accounting for atmospheric dispertion, and other things that are not able to be duplicated here on earth. ------------------------------------------------------------------------- Rob Dale ++ N8GSK .=. tippy!fireman Purdue University .=. @newton.physics Atmospheric Sciences .=. .purdue.edu ------------------------------ Date: 27 Oct 89 13:52:37 GMT From: philmtl!philabs!briar.philips.com!rfc@uunet.uu.net (Robert Casey;6282;3.57;$0201) Subject: Re: PowerSat Options In article <1488@crdos1.crd.ge.COM> davidsen@crdos1.UUCP (bill davidsen) writes: > Why would a microwave link be less dangerous? Is there some reason I >miss why a large beam pointed at a city wouldn't do what a radar beam >does to birds? I remember seeing a discription of a microwave powersat that indicated that a ground base microwave dish placed in the center of the power recieving area is used to transmit a pilot frequency to the powersat. The powersat would recieve this signal, doulbe the freq, and transmit the power back to Earth. The idea is if the powersat's aim goes bad, the powersat won't hear the pilot freq, and the powersat would shut down because there's no frequency to double. There's no on board oscillator to drive the powersat's transmitter, it's on the ground. You'd put the recieving area away from where anyone lives. ------------------------------- better dead than red! ------------------------------ Date: 28 Oct 89 05:02:57 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: Launch Advisory: COBE launch delayed (Forwarded) Jim Cast Headquarters, Washington, D.C. George Diller Kennedy Space Center, Fla. LAUNCH ADVISORY: COBE LAUNCH DELAYED The planned Nov. 9 launch of the Cosmic Background Explorer (COBE) spacecraft from Vandenberg Air Force Base, Calif., has been delayed until Nov. 19. In addition to a delay which occurred when the McDonnell Douglas Delta launch support team was required on the East Coast to support a recent Department of Defense mission, the COBE was further delayed due to a leak in the Delta launch vehicle's second stage fuel tank shutoff valve -- a valve which must be replaced. ------------------------------ Date: 29 Oct 89 17:44:28 GMT From: rochester!dietz@pt.cs.cmu.edu (Paul Dietz) Subject: Re: PowerSat Options In article <1729@bucket.UUCP> leonard@bucket.UUCP (Leonard Erickson) writes: >>A powersat's aperture would be small, so it could not form an intense >>beam at the earth's surface. The power density would be far lower >>than in BMD applications. This weapons application stuff is a canard. > >I'd expect the beam to be more like 15 *giga*watts! And one thing you'd >have to worry about if powersats were "common" is what happens if your >friendly neighborhood military types get the beam redirected to power a >space based weapon of some sort? Sigh, yet another canard. This person has beam-o-phobia. The power density of a powersat beam is low. A space-based weapon with a rectenna several miles across would be absurdly vulnerable. By similar logic, we should not have a chemical industry (suppose the military used it to make explosives?) or metallurgy (used to make weapons) or even agriculture (they could make C rations). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 26 Oct 89 14:02:14 GMT From: crdgw1!crdos1!davidsen@uunet.uu.net (Wm E Davidsen Jr) Subject: Re: PowerSat Options In article <1335@orbit.UUCP>, schaper@pnet51.orb.mn.org (S Schaper) writes: | The CPSU would take a dim view of a 15 megawatt laser in orbit. So would the | UN. Actually a maser would be better, as it should penetrate cloud cover, I | think, but it too, has that weapons potential Why would a microwave link be less dangerous? Is there some reason I miss why a large beam pointed at a city wouldn't do what a radar beam does to birds? -- 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 ------------------------------ End of SPACE Digest V10 #187 *******************