Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from corsica.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests) ID ; Thu, 7 Sep 89 03:17:14 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Thu, 7 Sep 89 03:17:05 -0400 (EDT) Subject: SPACE Digest V10 #27 SPACE Digest Volume 10 : Issue 27 Today's Topics: Re: Eugene Cernan talks for dollars Re: Voyager Pictures moved to another machine Electric Rockets NSS Hotline Update Re: Pluto fly-by Re: NASA Headline News for 08/30/89 (Forwarded) Solar sails (was Re: Pluto fly-by) Voyager Neptun/Triton Encounter Re: Pluto fly-by Re: Post- Star Wars space habitability ---------------------------------------------------------------------- Date: 30 Aug 89 22:30:33 GMT From: dptg!pegasus!psrc@rutgers.edu (Paul S. R. Chisholm) Subject: Re: Eugene Cernan talks for dollars In article <726@ac.dal.ca>, arppeter@ac.dal.ca writes: > In article <423@huxley.UUCP>, steve@huxley.UUCP (Steve Stein) writes: > > Astronaut Captain Eugene Cernan . . . will be speaking . . . > > Tickets are $12 for an adult, $10 for children. Proceeds will > > benefit the Acton Discovery Museums. > > There will be a reception . . . tickets are . . . $35 apiece. > Whew, steep prices! I am not surprised to see these costs when I > realize it is for a "good cause". However, Gene came and spoke to > my High School Graduation Class in rural Calgary back in 1980. > There was no charge. . . . You have to differentiate what the *museum* is charging (it's advertised as a fund raiser), and what Dr. Cernan is charging. And even if Dr. Cernan is getting paid, it's understandable. I've helped organize a few space-related events at the New Jersey State Museum. We've had a couple of former mission specialists speak; they seemed to like it, they did a great job, and their audiences ended up both better informed and more enthusiastic about space exploration. After a few years, one stopped volunteering; the other sadly informed me that he had to charge a fee, normally such-and-such, for appearances. (He did last year's Spaceday at the museum for half price.) He wasn't (and isn't) greedy; he just had to cut back, somehow, on the number of appearances he makes, and the easiest way to separate the enthusiastic from the polite was to charge a speakers fee. You would not *believe* the number of kids and parents who came up to him and said, "I saw you when you came to my school." (This past Spaceday, it seemed impossible to get *anyone* who flew, unless you wanted to bring them to Houston, the Cape, or D.C.) > Peter J. Russell, Bitnet: ARPPETER@AC.DAL.CA or OFFSHOR@TUNS.CA Paul S. R. Chisholm, AT&T Bell Laboratories att!pegasus!psrc, psrc@pegasus.att.com, AT&T Mail !psrchisholm I'm not speaking for the company, I'm just speaking my mind. ------------------------------ Date: 30 Aug 89 07:29:57 GMT From: agate!shelby!portia!hanauma!joe@ucbvax.Berkeley.EDU (Joe Dellinger) Subject: Re: Voyager Pictures moved to another machine In article <1590@ncrcan.Toronto.NCR.COM> tim@ncrcan.Toronto.NCR.COM (Tim Nelson) writes: >O.K. it is nice that you are moving the pictures, but are they available >anywhere to those of us who do not have access to FTP? >(perhaps anonymous uucp?) Sorry, I can't really get into mass e-mailing or uucp'ing the images; ftp'ing them has been enough of a headache. However, there must be more than a thousand copies of those images out there by now, so you might be able to find some nearby machine that could get them to you. Even better, is there anybody out there that already maintains an anonymous UUCP site, and could easily add them to their archive? (If you are such a site and willing to do this, but don't have ftp, send me e-mail.) The main image file, containing what I thought were the 7 best pictures we digitized, is a little over a megabyte. Is that too big for anonymous UUCP? \ /\ /\ /\/\/\/\/\/\/\.-.-.-.-.......___________ \ / \ / \ /Dept of Geophysics, Stanford University \/\/\.-.-....___ \/ \/ \/Joe Dellinger joe@hanauma.stanford.edu apple!hanauma!joe\/\.-._ ------------------------------ Date: 30 Aug 89 13:59:02 GMT From: rochester!dietz@PT.CS.CMU.EDU (Paul Dietz) Subject: Electric Rockets In article <6097@lynx.UUCP> neal@lynx.UUCP (Neal Woodall) writes: >Please, some details!! Perhaps we can start a thread on "exotic" thrusters >which would be good for the next generation of planetary probes. I am >interested in any engine that allows continuous thrust for long periods of >time, and will probably be of very high specific impulse. I have no info >on the MPD engine you speak of...... One place you might look is in: Progess in Astronautics and Aeronautics, Vol 79, Electric Propulsion and Its Application to Space Missions (Robert Finke, ed.). AIAA, 1981. This volume also has several articles on the LeRC 30 cm Hg-ion engine, and the European RIT 35 Hg-ion engine, in addition to a section on MPD thrusters. MPD thrusters accelerate a plasma using Lorentz forces -- the force exerted by a magnetic field on a perpendicular current. In the self-field MPD thruster, the magnetic field is generated by the current pulse itself. As I understand it, MPD thrusters are not as efficient (maybe 50%) as ion engines (maybe 70-80%), but are much smaller. To operate at top efficiency, an MPD engine needs a lot of power (~ 1 MW), so in low thrust applications they would operate with low duty cycle -- the inefficiency in storing energy would be more than made up for by the increased engine efficiency. I seem to recall some more recent work on an "afterburner" for an MPD engine that would use the plasma exhaust to heat a light gas, thereby reducing the exhaust velocity and increasing thrust for a given quantity of input power (references?). An MPD engine might make sense in high power missions. For example, a nuclear-electric vehicle to Mars (8 MWe argon MPD thrusters; see AAS 86-172 in the 1986 NASA Mars Conference). According to that article, this NEP option would be quite favorable for a 15-year, 20 person Mars base (in terms of expandable mass) in comparison with chemical propulsion, even with propellant manufacture at the moons of Mars or at Earth's moon, but would require much more powerful space reactors than are currently available. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 30 Aug 89 15:01:00 GMT From: cdp!jordankatz@labrea.stanford.edu Subject: NSS Hotline Update This is the National Space Society's Space Hotline for MONDAY, August 28. The NSS was host to two successful fundraising events this last week in California during the Voyager encounter with the planet Neptune. NSS Board members hosted a reception on Friday, August 25 at the California Institute of Technology in which members of the STAR TREK original series attended, as well as hundreds of NSS members, and other special guests. Saturday, August 26th saw a reception/buffet at the Paramount Pictures studios on the set of ST:TNG. Nearly the entire cast of ST:TNG, along with BOD Gene Roddenberry, BOG Hugh Downs, NSpC ex Secy Mark Albrecht and family, NASA assoc admn for space science applications Dr Lennard Fisk, Buzz Aldrin and a number of NSS members and board members. The entire group got a chance to sit in the Captain's seat on the bridge as well as to get beamed up! The Voyager II spacecraft's encounter with Neptune has been a spectacular success. Images and scientific data continue to pour in and are analyzed. Among the findings are that there may be 5 rings encircling Neptune, the giant storm, in the great spot may have winds up to 716 mph, and that active ice volcanoes may be occuring on Triton. This would be 3rd body in solar system to have active volcanoes The first commercial rocket to carry a satellite into orbit was launched from the Cape Sunday evening at 6:59pm. McDonnell Douglas launched the three-stage Delta 187 booster with a 2,700 lb Marcopolo 1 satellite for the British Satellite Broadcasting service. The space shuttle Atlantis will be moved to launch pad 39B beginning at 12:01 am EDT on Tuesday, 8/28. This has been David Brandt for the NSS space hotline for Monday august 28. ------------------------------ Date: Wed, 30 Aug 89 09:34:42 PDT From: Peter Scott Subject: Re: Pluto fly-by hess@fermat.mayo.edu (d. scott hess) writes: > One proposal I've heard for >light-sail launching says that the best way to launch (without large >moon or space based lasers) would be to put it on an asteroid, and drop >it into a cometary orbit around the sun (heck, put it on a comet), and >then jumping off with your "sail in the wind", so to speak. This get >you a fair amount of "free" velocity, plus you make the most of the >inverse-squared nature of light. Maybe even getting a boost from the >solar wind. A talk on solar sails at Planetfest last week revealed that one plan for getting some really spectacular velocity out of a solar sail is to hide it behind an opaque disk, and fly it in really close to the sun, then jettison the disk with a florish and ride the photons while they're fresh. I forget what kind of velocity that produces but it does get the highest velocity you can attain with a s.s.. Certainly at the Earth's orbit the contribution of the solar wind to s.s. thrust is less than 1%, so don't expect much help from that. This talk was given by a member of the World Space Foundation, one of those organizations like Space Studies Institute that spends less time talking and more time building neat stuff, like a solar sail, in their case. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 31 Aug 89 02:34:39 GMT From: aramis.rutgers.edu!athos.rutgers.edu!masticol@rutgers.edu (Steve Masticola) Subject: Re: NASA Headline News for 08/30/89 (Forwarded) Peter E. Yee writes: > Voyager 2 is continuing its journey outward and is now almost > five million miles from Neptune. Next spring, mission managers > will turn the spacecraft's cameras, infrared detector and light > sensors off to preserve power. Can the RTG be conserved by reducing power use, or are the instruments being shut off because there won't be adequate power available for them at that time? The former seems unlikely, unless the fission rate in the RTG can be controlled. > Scientists should be able to track Voyager for another 25 years > until its power supply expires. When is Voyager expected to meet the heliopause? Was any maneuvering done at Neptune to shorten this time? - Steve (masticol@athos.rutgers.edu) P.S. Please, please, don't let what happened to ALSEP happen to Voyager! ------------------------------ Date: 31 Aug 89 06:18:13 GMT From: unmvax!ogccse!blake!wiml@ucbvax.Berkeley.EDU (William Lewis) Subject: Solar sails (was Re: Pluto fly-by) Presumably in an article, pjs@ARISTOTLE-GW.JPL.NASA.GOV (Peter Scott) writes: >A talk on solar sails at Planetfest last week revealed that one plan for >getting some really spectacular velocity out of a solar sail is to hide >it behind an opaque disk, and fly it in really close to the sun, then >jettison the disk with a florish and ride the photons while they're fresh. >I forget what kind of velocity that produces but it does get the highest >velocity you can attain with a s.s.. [ .... ] Now, I don't claim to be an expert on solar sails at all, but this doesn't sound quite right.... An opaque disk would only cut the thrust by half, ignoring the solar wind, or by less than half if the solar wind is non negligible. It would be much, much better (IMUO) to drop in keeping the sail edge-on to the sun (if you use a flat one), or not unfolding the sail until you get there. Say, if you use a spinning sail, the second is easier, but if you use a rigid sail, probably the first is doable. (Myself, I don't trust wires to keep my sail in place, or active systems to keep it aligned ... I prefer conical spinning sails ... but I'll leave that to the people who know about masses and strengths and whatnot in more detail.. i.e, not me.) [halfserious mode on...] what this network needs is a sci.space.sf-lovers group. That way I can be enthusiastic about things without worrying about reality and all that nasty stuff. [mode off] --- phelliax --- wiml@blake.acs.washington.edu --- gee, that looks almost like a signature. ------------------------------ Date: Thu, 31 Aug 89 08:52:47 MEZ From: OE2N%DLRVM.BITNET@VMA.CC.CMU.EDU Comment: CROSSNET mail via MAILER@CMUCCVMA Date: 31 August 1989, 08:25:20 MEZ From: OE2N at DLRVM bitnet Peter Seige To: SPACE at ANDREW.CMU.EDU Subject: Voyager Neptun/Triton Encounter The last few days I heard and read a lot about Voyager encounter with NEPTUN and TRITON. So far I could not get any good information about the maximum resolution of the images during these encounters. Is there anybody (probably from JPL) who can get me more informations about that. Peter Seige ------------------------------ Date: 31 Aug 89 06:00:17 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Pluto fly-by Unveiling a solar sail near the Sun would be fun, but as previously discussed here it's very expensive powering something there to begin with. -- "We walked on the moon -- (( Tom Neff you be polite" )) tneff@bfmny0.UU.NET ------------------------------ Date: 31 Aug 89 05:58:51 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Post- Star Wars space habitability I think near-earth space is about as uninhabitable as it's going to get. :-) Killing ICBMs with SDI won't itself pollute space with debris, because the things being zapped are ballistic and suborbital. The debris will re-enter. If it ever happens, worry about the ecosphere not space, because SDI won't get 'em all. ASAT warfare could make space crunchy underfoot. SDI is just a tempting set of targets. -- "We walked on the moon -- (( Tom Neff you be polite" )) tneff@bfmny0.UU.NET ------------------------------ End of SPACE Digest V10 #27 *******************