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 ; Mon, 16 Apr 90 01:30:58 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 16 Apr 90 01:30:27 -0400 (EDT) Subject: SPACE Digest V11 #263 SPACE Digest Volume 11 : Issue 263 Today's Topics: Galileo Update - 04/13/90 Re: Interstellar travel Re: Silo Launches etc. Re: Pegasus launch from Valkyrie (or ... Re: releasing data / digitized images Re: releasing data / digitized images Re: Silo Launches etc. ---------------------------------------------------------------------- Date: 15 Apr 90 08:36:03 GMT From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Galileo Update - 04/13/90 GALILEO MISSION STATUS REPORT April 13, 1990 As of noon Friday, April 13, 1990, the Galileo spacecraft is 85,179,540 miles from the Earth, 14,722,470 miles from Venus and traveling at a heliocentric velocity of 76,850 miles per hour. Round trip light time is 15 minutes, 10 seconds. The spacecraft is in cruise mode-dual spin with a spin rate of 3.15 rpm. The spacecraft attitude sun point angle is 0.7 degrees. Telemetry rate is at 40 bits/second through the Low Gain Antenna (LGA-1). The sequence memory load for the first portion of the Trajectory Course Maneuver (TCM-4A) was transmitted and received without incident on April 8. A SITURN to lead the sun was successfully performed on April 8 in preparation for the TCM-4A maneuver execution on April 9. The SITURN magnitude was selected to provide a near sun-pointed attitude at the start of the maneuver. Another SITURN to lead the sun was successfully performed on April 13 after completion of all manuever activities. The first portion of TCM-4A was successfully completed on April 9. Preliminary assessments indicate that spacecraft performance, in general, was well within predicted limits. For the first three burn segments, the total system performance was excellent. During the last three burn segments, some increases in pointing error were observed reaching about 11.5 mrad at the end of the final burn (well within predictions). This pointing error was subsequently reduced to about 1 mrad via a sequence planned pointing correction. It was further observed during this same period that the DC bus imbalance measurement increased about 1.5 volts (12 DN) to near 19 volts. When firing was completed, the DC bus imbalance measurement returned close to its initial pre-burn value; no significant change was noticed on the AC imbalance measurement. The RPM L-thruster temperature profiles observed during the first burn segment were lower than predicted and reached a peak of about 158 degree C and 135 degree C for the L1B and L2B, respectively (predicted level up to 170 degree C). Very early into the second burn segment, the L2B temperature measurement went to a saturated reading of 255 DN. The measurement appeared instantaneously to go from the expected 115 DN to 255 DN. This profile characteristic is similar to that seen during TCM-1 when the Z1A temperature instantaneously went to 255 DN indicating a likely transducer failure. It is important to remember that the thruster temperature transducers were added late in the program to provide additional thruster thermal visibility and were installed using an unqualified attachment method and their installation was accepted by the project on a "best-effort" basis. The sequence memory load for the second, third and fourth portion of TCM-4A were transmitted and received without incident on April 9, 11, and 12, respectively. The second maneuver portion of the TCM-4A was successfully completed on April 10. Prior to the start of burns in this portion, a SITURN was performed as planned to bring the spacecraft to a near sun-pointed attitude. Spacecraft performance was again within predicted levels, however, some performance differences were observed from the first maneuver portion on April 9. Significant differences included a larger cumulative pointing error (almost 18 mrad vs 11 mrad after the last burn segment) but still within the predicted range. In addition RPM tank pressures were about 0.2 bar lower than predicted. The pointing error was subsequently corrected to near one-half mrad with a planned sequence pointing correction. The DC imbalance measurement during the second portion again exhibited a profile similar to that observed during the first portion and again very little change was reported in the AC imbalance reading. The third portion of TCM-4A was successfully performed on April 11. Similar to the second portion, a SITURN was performed prior to the burn. Pointing errors continued to exhibit some unexplained growth during this portion. The cumulative error after the first three burn segments was about 18.2 mrad. A planned correction was performed reducing the error to about 1 mrad prior to the start of the next three burn segments. The next three burn segments caused a cumulative pointing error of about 22 mrad. The planned pointing correction near the end of the sequence reduced the error to near 3 mrad. During this third portion, the RPM tank pressures were observed to be about 0.4 bar lower than predictions but well within acceptable performance limits. The L1B thruster temperature profile was nearly identical to that observed in maneuver portions one and two and well within predicted levels. The DC and AC bus imbalance measurements during this portion changed only 1 DN significantly different from the 12 DN range observed in maneuver portions one and two. The fourth and last portion of TCM-4A was successfully performed on April 12. Similar to portions two and three a SITURN was performed prior to the start of the burn activity. The cumulative pointing error at the end of first three burn segments was 20.2 mrad which was corrected to approximately 2 mrad via the sequence planned pointing correction prior to the start of the fourth burn segment. At the end of the sixth portion the pointing error was 23.2 mrad. This error was corrected down to about 4 mrad via the planned sequence pointing correction. RPM tank pressures gradually dropped from 17.6 to 17.0 bar during burn segments, a little lower than predicted levels. Once again the L1B thruster temperature was stable near 158 degree C similar to all other burn segments. The DC and AC imbalance measurements remained very stable throughout this maneuver portion varying about one DN. Preliminary Navigation Analysis has indicated that the TCM-4A imparted very near the required delta velocity (24.8 m/sec) with a slight total under burn of about 0.48 m/sec (1.7 sigma). Despite pointing error changes, RPM tank pressures being a little lower than predicted in some segments, and the apparent loss of the L2B temperature transducer, the spacecraft system performance was good throughout the four-day, 24-segment burn manuever. This is the first time that the L-thrusters have been used exclusively for a large delta velocity burn. The number of L-thruster pulses in the TCM-4A was more than 10 times the number used to date for the entire mission. It is very possible that the performance changes observed could be attributed to prediction modeling fidelity of this "new" operating condition. Ron Baalke | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | ------------------------------ Date: 13 Apr 90 17:27:18 GMT From: elroy.jpl.nasa.gov!aristotle!pjs@lll-winken.llnl.gov (Peter Scott) Subject: Re: Interstellar travel In article <20192@megaron.cs.arizona.edu>, kline@cs.arizona.edu (Nick Kline) writes: > So what is the Fermi Paradox? Is this the equation where you try > to estimate various factors which relate to the chances of intelligent life, > like say % of suns with planets, % with life, % with intelligent life, > % with life that doesn't destroy itself, similar in scope to the equation in > Cosmos, by Carl Sagan? Nope, that's the Drake equation. The Fermi paradox basically says, "Where is everybody???" The Drake equation suggests that the galaxy should be teeming with life, given the number of stars we have. *Our* presence as a technological society can readily be detected within a 50ly radius; yet we have found no signs, similar or other, that life exists elsewhere in the universe. Speculation as to why this is the case runs rampant and I refer you to some excellent pop science discussions of same in _Analog_. This is news. This is your | Peter Scott, NASA/JPL/Caltech brain on news. Any questions? | (pjs@aristotle.jpl.nasa.gov) ------------------------------ Date: 13 Apr 90 17:29:16 GMT From: dfkling@june.cs.washington.edu (Dean F. Kling) Subject: Re: Silo Launches etc. >What about the operational silos at the bases? I remember hearing that a >Titan II had exploded in a test launch from an operational silo thus putting >an end to them, is this my faulty memory ? Also there was a report a >while back of an accidental Titan II launch. Is this an urban legend or >is there some truth to it? Several years ago there was an accidental explosion in an operational Titan silo (I think in Arkansas) which resulted in the warhead being "launched" into a nearby potato field. As I recall the root cause of the accident was a very large socket (and maybe wrench) being dropped inside the silo, falling dozens of feet, rebounding off a structural member and puncturing the fuel tank. Some time later, the spilled fuel/fumes exploded, destroying the silo. There was a follow up sometime later on "60 Minutes" which focused on an enlisted airman who, after preforming heroics to combat the accident, was punished by the AF for violating nuclear weapons access rules ( e.g. Two Man Rule for access to a weapon). I don't believe any of this involved an attempt to do a test lanunch for the same reasons as Minuteman, the first stage has to come down somewhere unpleasant for launch azimuths with acceptable impact points. Dean dfkling@cs.washington.edu ------------------------------ Date: 14 Apr 90 06:32:49 GMT From: skipper!shafer@ames.arc.nasa.gov (Mary Shafer (OFV)) Subject: Re: Pegasus launch from Valkyrie (or ... In article <4634@cbnewsj.ATT.COM> johna@cbnewsj.ATT.COM (john.a.welsh) writes: >We have seen here that if you want to launch more with a Pegasus, >you need more speed in the booster plane. There is only 1 B70 >left, and I don't think the Airforce Museum in Dayton will let >anybody use it (who would certify it air worthy, too?). Somehow, I don't think that flying a stainless steel airplane that's sat outside at Wright-Patterson, in the rain and snow, for over a decade is a real good idea. I saw the rust weeping from it. >So how >about the next fastest bomber, the B58? Were they all broken >up or are there other museum pieces around (other then Dayton's)? When last I looked, there was a B-58 sitting on the lakebed just off Mercury Drive here at Edwards, destined for the museum. Of course it's sat outside at Edwards, in the rain and snow, for over a decade, but we have a lot less rain and snow and it's not stainless steel, so it's probably a better idea. >A B58 held the coast to coast record that the SR71 broke (LA - NY >in about 2 hours) and they were in regular airforce service, so >they were not experimental oddities. They had external pods so >they could carry more than their bomb bays could hold, though I >am not sure if they could go supersonic with the pods (I think >they could). If we are discussing B70s here, why couldn't we have >a B58 launch Pegasus? The only drawback I see at first glance is that the B-58 is too close to the ground. The gear wouldn't touch if there was a Pegasus under the wing. But this is also true of the F-111 and someone proposed a mag-lev cart for takeoff. I believe that a largish fighter has taken off using a ground-effect cart, rather than gear (although I can't confirm this 'til Monday, when I get to work and references). Or you could put gear on Pegasus. Or use fall-away gear like the outriggers on the U-2. Actually, I thought that a large, high-wing plane like the C-5 or C-141 would be the easiest to modify, but they're so _slow_. -- 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 ------------------------------ Date: 16 Apr 90 01:45:33 GMT From: att!cbnewsh!lmg@ucbvax.Berkeley.EDU (lawrence.m.geary) Subject: Re: releasing data / digitized images In article shafer@skipper.dfrf.nasa.gov (Mary Shafer (OFV)) writes: > >I've got to ask; my curiosity has gotten the best of me/ > >Why do readers of this group want images and data from HST? Research? >Pretty pictures? A new display on an idling Mac or Sun? (There's a >moon picture that very popular here for this last use.) I don't want digital data. I have no use for it. However, the *impression* I have is that, while Voyager images were broadcast live over NASA Select and were immediately available to everyone, HST images (digital or any other form) will be hoarded for a year or more by investigators; that maybe sometime down the road we'll get a postage stamp sized image in Sky&Telescope or an occasional article in the newspaper, but that otherwise the torrent of new discoveries will be unavailable outside of esoteric academic journals. I don't know about you, but the information released to the press by NASA last summer during the Voyager encounter with Neptune made me feel like a participant in the discovery process. It felt great! If NASA broadcast a 15 minute daily summary of HST news and images, and if it was available to us in some way, I'd be really happy. But we all know the news media will be tired of HST in a week or two, and if there isn't some other way of getting the images we'll be cut off and locked out of the process. Probably we should think of HST as just another big telescope; after all, nobody is demanding an archive of images from the Hale telescope on Palomar, are they? But because it's a NASA spacecraft, some of us are looking forward to a 15 year long "encounter". Maybe we shouldn't. --Larry -- --Larry: 74017.3065@compuserve.com ------------------------------ Date: 13 Apr 90 21:29:53 GMT From: skipper!shafer@ames.arc.nasa.gov (Mary Shafer (OFV)) Subject: Re: releasing data / digitized images I've got to ask; my curiosity has gotten the best of me/ Why do readers of this group want images and data from HST? Research? Pretty pictures? A new display on an idling Mac or Sun? (There's a moon picture that very popular here for this last use.) I haven't seen any reason except easy pretty pictures, but surely you have other good reasons to want them. (There's nothing wrong with just _wanting_ them, BTW, or with wanting pretty pictures.) I'm sure that everyone on this group knows that you can borrow large negatives/transparencies of virtually all of the pretty pictures from Apollo, etc, from the NASA Archive. I had some beautiful prints made of the Moonrise and Whole Earth. The borrowing is free, but you have to have the prints made. I also suspect that it may be a while before HST photos are available. -- 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 ------------------------------ Date: 13 Apr 90 01:09:53 GMT From: vsi1!hsv3!mvp@ames.arc.nasa.gov (Mike Van Pelt) Subject: Re: Silo Launches etc. In article <2477@syma.sussex.ac.uk> nickw@syma.susx.ac.uk (Nick Watkins) writes: >What about the operational silos at the bases? I remember hearing that a >Titan II had exploded in a test launch from an operational silo thus putting >an end to them, is this my faulty memory ? Also there was a report a >while back of an accidental Titan II launch. Is this an urban legend or >is there some truth to it? I don't know about the test launch, but some time back, a worker at a Titan silo in Arkansas dropped a tool, and it punctured the missile's fuel tank. Very large explosion as lots of UDMH and nitrogen tetroxide combine hypergolically... The warhead was found later, some distance away. The Titans were decommissioned soon after that, but I don't think this was the reason; I think the decommissioning was already scheduled. -- Mike Van Pelt Windows + Icons + Mouse Headland Technology/Video 7 + Pointer == WIMP. ...ames!vsi1!v7fs1!mvp ------------------------------ End of SPACE Digest V11 #263 *******************