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 ; Fri, 1 Feb 91 02:32:59 -0500 (EST) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 1 Feb 91 02:32:52 -0500 (EST) Subject: SPACE Digest V13 #101 SPACE Digest Volume 13 : Issue 101 Today's Topics: Re: Satalite/IS Probe manual Re: W. Larrison's Re:Fwd: NASA Plans To Redesign Space Station Comparing reliability [Part 1 of 2] ROSAT Update - 01/28/91 Magellan Update - 01/28/91 Re: Request for Feedback on Proposed Lunar Analog Robotics Contest Re: More on space cameras 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: 29 Jan 91 04:28:54 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: Satalite/IS Probe manual In article <1991Jan22.154422.4855@d.cs.okstate.edu> rjs@d.cs.okstate.edu (Roland Stolfa) writes: >1. Is there a "manual" that describes what kinds of things a space > probe must be capable of in order to maintain trajectory? Try "Spacecraft Attitude Determination and Control", ed by James R. Wertz, Kluwer 1978. This is pretty much the bible on the subject, and it is still in print. It is expensive and 850+ pages. A non-trivial subject. >2. Are there actual "manufactures" of space probes? By this I mean > is there any company that might just have a manual on how to "harden" > a space craft for flight, what kind of redundancy is needed, etc. > or is all of that kind of information classified beyond the reach > of the average mear-mortal? :-) Not classified, but not published much either. There are only a handful of satellite manufacturers, and except for a couple of books on comsats, I'm not aware of any in-print technical books on the details. Demand is too limited to justify a lot of publishing on the topic. I would also suspect that some details are proprietary; it's a very competitive market. >3. I seem to remember that some of the earlier space probes had > core memory and 9-track tape players in them. Are current probes > still using this kind of stuff for some "hardening" reason, or is > it out of vogue? Magtape is still in use, although I don't think modern birds -- ones designed today, that is, bearing in mind that some old designs are still in use -- are still using core. NASA has been persistently interested in solid-state replacements for magtape, since tape recorders are historically a reliability trouble area, but none has yet flown that I know of. Space qualification requires very high reliability and considerable radiation resistance. >4. I have never seen referenced what kind of (and or quanity for that > matter) processors are on space probes. Do any of them use stock > CPU's or are they more likely to use custom units and why? A little of both. Space-qualification requirements rule out a lot of routine commercial hardware. Once the list has been thinned down, the choice is made based on the requirements of the mission. Stock CPUs are used for undemanding things, with custom designs more common when computing requirements get stiffer. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 29 Jan 91 04:35:22 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: W. Larrison's Re:Fwd: NASA Plans To Redesign Space Station In article dlbres10@pc.usl.edu (Fraering Philip) writes: >3. Maybe these disturbances don't really matter that much (?)(just >guessing again). After all, a lot of noisy microgravity with people on >hand might be better than a small amount of 'Perfect' microgravity. Actually, both have their uses. The space-station microgravity people were originally very happy about finally having an *interactive* microgravity lab, where they could modify experiments in real time instead of getting one test every few years. (Said happiness faded as the available power, astronaut time, and facilities kept shrinking.) But there is also an important role for long periods of uninterrupted high-quality microgravity, which pretty much requires an unmanned free-flier. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Tue, 29 Jan 91 00:19:03 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Comparing reliability [Part 1 of 2] >From: aws@ITI.ORG ("Allen W. Sherzer") >Newsgroups: sci.space >Subject: Why man rate? (was: space news from Dec 17 AW&ST) >Date: 25 Jan 91 00:25:59 GMT [Part 1 of 2] In the months that this has been debated, I have come to the tentative conclusion that the comparison of launch success rates of various systems is not really deserving of the heat that has sometimes been generated. Aside from questions of accuracy of the calculations, it's really not practical to come up with a single number that adequately describes the performance that can be expected. With the more valid approach of a complex statistical analysis, there will often be situations in which one system or the other will be considered better, depending on the exact task to be performed. Nevertheless, overall ratings do give some information, so discussion is worthwhile as long as people take it with a grain of salt (like the college football team ratings :-). >>I just got out some Martin Marietta literature on the Delta. In it they >>advertise a launch success rate of 93.9%. >You need to look deeper since Martin makes the Titan not the Delta. They >will fudge the figures to make Titan look better. >In the entire 30 year history of the Delta this is an accurate figure. >However, their success rate over the last 13 years is 98.33%. And of course the pro-Delta folks will want to use the figures that make Delta look good, though I believe they will still make an effort to be fairly accurate. A few months ago I saw a 1989 Delta promotional film that used the figure of 96%, which I believe was their prediction for the success rate of upcoming launches. That *is* a good rate by current standards, better than Ariane (I think). Both Delta and the Shuttle are sufficiently reliable and have flown a sufficiently small number of missions that operational records are not really an extremely accurate predictor of future performance, and the continual improvement of both systems makes the job even harder. For instance, before the last Challenger flight, the Shuttle had a 100% success rate, which was clearly not a good predictor. Immediately after Challenger, the overall success rate was something around 96%. Analysis of the accident revealed that it was the result of a failure mode that had previously received inadequate attention, namely the stiffness of the solid booster O-rings at low temperatures. That failure mode was pretty much eliminated, as well as many others that turned up during the investigation. The net effect was to make the Shuttle even more expensive to operate, but hopefully safer. After the changes, there are three approaches for using launch success rate as an indicator of future performance: (1) regard the Shuttle as a completely new craft, with only a small number of launches, and thus not much direct evidence for good future performance, (2) continue to keep a tally from the start of the Shuttle program, thus equating the old and new systems, or (3) start with the same number as in method (2), but consider that since known failure modes have been eliminated or reduced in likelihood, the indicated success rate is actually higher than the number produced by (2). Methods (1) and (2) basically reflect a concern that the modifications may introduce significant new failure modes. My own opinion is that extensive analysis and the launches since Challenger do not *appear* to have turned up introduced failure modes, so the indicated future performane probably *is* higher than the overall success ratio to date. >Independant >estimates of Shuttle success rates put it at about 95% and it's operational >record so far is about 96.66%. It's hard to keep count with the mission numbers all out of sequence, but I *think* that there have now been either 39 or 40 launch attempts, one of which failed. This puts the operational record at around 97.4%, with, as I said, some hope that the known repairs make the performance-based prediction of future reliability somewhat better than that. The 95% figure is about the most pessimistic available, thus often used by companies who want to promote alternates to the Shuttle (fair enough, I suppose). NASA's best attempt at an accurate estimate, which they claim to be based on a fairly conservative analysis, is that reliability (in terms of loss of orbiter, I think) is somewhere in the range of 98.5-99%. (They have a single number as a best guess, but I forgot what it was.) This translates roughly to one or a couple of orbiter losses expected over the lifetime of the Shuttle program, an estimate which NASA does not now attempt to hide. I think it is clear that before Challenger, NASA Shuttle reliability estimates were rather poor, based on excessive optimism, and without much effort to make sure that they were accurate. After Challenger and the blast of criticism, NASA has a tremendous incentive to present risk estimates that are as realistic as possible, lest they be accused of dishonesty in the event of a future accident, and they are known to have expended vastly more effort on risk analysis than had previously been the case. I think it is also interesting that they tend to avoid public use of their estimate except when forced to by congressional hearings, etc., which may indicate that their number is lower than they would like. One might speculate that if they did not feel constrained to produce an accurate "best guess" or conservative number, then they would have come up with an estimate that they would be happy to brag about. Added to the fact that NASA knows much more about the Shuttle than anyone else and has a tremendous base of knowledge in launch systems, this tends to make me believe that the NASA estimate of Shuttle reliability is *probably* the most accurate estimate that we can currently hope for, and even then it *may* turn out to be a little on the conservative side. All of which, of course, is not much comfort if there *is* an accident resulting in loss of shuttle or human life, except perhaps as some reassurance that such loss was the result mostly of chance rather than of gross negligence (as seen in the commendable decision by the Soviets to resume immediate use of the Zenit boosters after one had exploded). No current launcher has anywhere near the safety record of commercial airlines. Another word on the use of "percent reliability" in general - if you are launching a hundred payloads of some bulk material and need to estimate how many extra loads to launch to make up for losses, this is indeed the best figure to use. If, however, you're launching a single device or a number of noninterchangeable components, and need to know the chance that there might be a failure (which could seriously hamper your project), then chance of failure (i.e. 1 in n) is the measure you need, and it's much better to deal with it that way. That's because for this use, and with highly reliable launchers, percent reliability is highly sensitive to even small errors. For instance, if you have a satellite you want to launch, and you know the launcher is considered either 98% or 99% reliable, that's only a ~1% uncertainty in the number you have, but 2 to 1 ratio in the odds of failure. Note that this caution mainly applies to use of the numbers in rough calculations - if sufficient care is taken, the two approaches are equivalent. [Continued in Part 2] John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 28 Jan 91 16:12:18 GMT From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@tut.cis.ohio-state.edu (Ron Baalke) Subject: ROSAT Update - 01/28/91 ROSAT STATUS REPORT January 28, 1991 The German Space Operations Center (GSOC) declared a spacecraft emergency for the Rosat spacecraft on January 26, 6:19 AM UTC. A 26 meter antennas was scheduled in real time to support the emergency. The spacecraft disconnected is on-board systems due to a loss of power. On January 26, 15:00 UTC, GSOC cancelled the emergency and the spacecraft was in standby mode. GSOC requested that 26 meter antenna in Madrid be used to support a boost manuever on the Eutlesat II-F2 satellite, since the Weilheim was pulled off for the Rosat emergency. The Madrid antenna was used to support the maneuver on January 26 from 8:30 AM through 9:28 AM (UTC), and the burn was successful. GSOC also reports that downlink was reestablished with the ROSAT spacecraft on January 27, 4:51 AM, using the Weilheim station. All spacecraft systems are operating nominally. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |___ M/S 301-355 | It's 10PM, do you know /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | where your spacecraft is? |_____|/ |_|/ |_____|/ | We do! ------------------------------ Date: 28 Jan 91 23:09:50 GMT From: swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucsd.edu (Ron Baalke) Subject: Magellan Update - 01/28/91 MAGELLAN STATUS REPORT January 28, 1991 The Magellan spacecraft and its radar system continue to perform nominally. All STARCALS (star calibrations) and DESATS (desaturations) of the weekend were successful. On January 25, the mapping command sequence M1026 was sent to the spacecraft, along with the associated parameter files. The 4-day sequence returned Magellan to its non-occulted mapping mode. Return to the normal Tuesday uploads will start with tomorrow's M1030 upload. Commands were sent up earlier today to perform the first of several in-flight tests of tape recorder "A". The tests will start at 11:20 AM PST and will include playback of data from two of the suspect tape tracks at 268 kbps and 115 kbps. The SAR (Synthetic Aperture Radar) Data Processing Team has processed standard image strips for orbits up to orbit #1111. Since Magellan is now on orbit #1370, it means that the team is processing radar image data from 35 days ago, that is, from Christmas Eve. This is because the processing of standard images must wait for data tapes to be shipped from the DSN (Deep Space Network) stations in Australia and Spain. During the first 40 days of mapping these tapes were "expedited" - delivered to JPL by courier - so that early images could be processed and evaluated quickly. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |___ M/S 301-355 | It's 10PM, do you know /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | where your spacecraft is? |_____|/ |_|/ |_____|/ | We do! ------------------------------ Date: 29 Jan 91 01:34:25 GMT From: deccrl!news.crl.dec.com!shlump.nac.dec.com!sousa.enet.dec.com!sndpit.enet.dec.com!smith@bloom-beacon.mit.edu (Willie Smith) Subject: Re: Request for Feedback on Proposed Lunar Analog Robotics Contest In article <9972@orca.wv.tek.com>, doughe@bamboo.WV.TEK.COM (Douglas E Helbling) writes... > > I am working toward putting together a robotic competition for small > rover-like vehicles. The contest would take place on the Oregon > desert at the Oregon Moonbase, an earth analog of a lunar lavatube. > The Oregon Moonbase is a project of The Oregon L-5 Society, Inc., a > chapter of the National Space Society. The robotics competition, > if it comes to reality, will probably take place in late 1992 or > early 1993. The Sunswick Engineering team will be there with the Tycho and Waldo vehicles if this happens. Just what we've been looking for! > b) Size - the current limit on physical size for the "unextended unit" > is two feet square. (Must fit in a box two by two by two feet.) > The notion that a robot could "expand" out of its shipping crate > after delivery (particularly for units basing their design on > insect models from the natural world) is acceptable. Aw, c'mon, make it a three-foot cube, so we can bring Waldo (the real thing) , instead of just Tycho (the toy). A few more things I'd like to see thrown in for good measure: 1) All teleoperated vehicles should properly emulate the 3-second speed-of-light communications delay. 2) Make the contest a little more useful, and ask that some useful work be performed. F'rinstance, clearing a landing field, digging habitat foundations, covering habitat modules, etc. Sounds like a blast, we'll be there! Willie Smith smith@sndpit.enet.dec.com smith%sndpit.enet.dec.com@decwrl.dec.com {Usenet!Backbone}!decwrl!sndpit.enet.dec.com!smith ------------------------------ Date: 28 Jan 91 15:27:27 GMT From: usc!sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1!watcgl!imax!hugh@apple.com (Hugh Murray) Subject: Re: More on space cameras In article <1991Jan25.042952.6050@uvm.edu> wollman@emily.uvm.edu (Garrett Wollman) writes: >Maybe the guy from IMAX Systems (is that still their name?) can talk a >bit about the "Large Format Camera" (which *is* one of theirs, >right?)... I remember seeing a feature on them on "Venture" about >three or four years ago, when they were just starting to make waves... > > >Does NASA pay to have the LFC up there (as a supply), or does IMAX--or >a file producer--pay to put it there, so that they can make a movie of >it later? > >-GAWollman > >Garrett A. Wollman - wollman@emily.uvm.edu > Imax Systems Corp. is the name of the company and IMAX(r) is the name of our motion picture system which encompasses a large film format (each frame is 2.74" wide by 1.91" high, oriented horizontally on standard 70mm film stock), special cameras and projectors, all patented. The space films have been co-sponsored by the Smithsonian and Lockheed. We have two cameras specially constructed for Shuttle use, an in-cabin camera and a cargo bay camera which sits in a can at the very rear of the cargo bay. Hugh Murray hugh@imax.com Imax Systems Corp. ------------------------------ End of SPACE Digest V13 #101 *******************