henry@utzoo.uucp (Henry Spencer) (07/02/89)
NASA abandons the notion of a serviceable design for the polar platform, reverting to a one-shot expendable approach. [Hard to avoid, given the lack of any way to service it...] NASA plans to build a ground-based radar system to assess how bad the small-space-debris problem is, specifically with reference to the space station. Existing radars track big pieces but not small ones. SDI budget cuts slip Zenith Star space-laser experiment two years, at least. Bush selects "Endeavour" as name of new orbiter, after Captain Cook's first command, used in exploration of the Pacific, including Alaskan waters. [As reported by others, AW&ST left out the "u" in the name.] Authoritative report that the Titan 34D launch on May 10 was a pair of strategic-forces comsats. [Said report was later retracted; it was a snoopsat instead. The comsat pair is still waiting for launch.] Magellan doing well en route, with daily star calibration maneuvers being done to assess gyro drift. A day before landing, the Atlantis crew replaced one of the orbiter's five general-purpose computers after it failed. The orbiter routinely carries a spare, and the crew are trained in the replacement procedure, but it took about four hours because the computers are behind some of the middeck lockers and are not easy to get at. Atlantis lands successfully at Edwards. Landing on the lakebed runway had been planned, but crosswinds were too strong and plans shifted to one of the concrete runways. The landing was made there with an 8kt crosswind, which suited NASA fine, as landing in a mild crosswind has been a test objective for quite a while. NASA proposes to switch much of the station's power system from solar arrays to a solar dynamic scheme. Solar-dynamic was originally put off to phase 2, but the technology has developed well and an important advantage has appeared: by using a phase-change heat-storage system, a solar dynamic system can maintain full output even when the station is in Earth's shadow. Doing the same for solar arrays requires large battery banks, which deteriorate and have to be replaced, to the tune of the equivalent of a dedicated shuttle mission every five years just for battery replacement. Solar-dynamic systems also make power growth cheaper, a significant issue since some feel the station is underpowered. The station would probably retain one modest solar array for emergency power. Station management has not yet approved the switch; general consensus seems to be that it may be a good idea but it's disturbing that such major changes are still showing up now. US and Soviet scientists propose monitoring firing of high-powered lasers into space by placing scattered-light detectors 1 km or so from suspected antisatellite-laser locations. This could help verify a laser-Asat ban. Soviet shuttle orbiter will appear at the Paris air show, contrary to earlier reports. It will be carried there on the new Mriya heavylift transport aircraft, which will also star at the show. [This report quotes Soviet aviation officials as saying that the Paris orbiter will be a test article, but I think it turned out to be Buran itself.] Space Services Inc. and Space Data Corp. selected as contractors for commercial sounding-rocket services being bought by NASA for materials science. Contracts are for two launches each, with options on two more. NASA science managers [now there's a job title for you... :-)] say that Soviet radarsat reactors will be a "nuisance" to the Gamma Ray Observatory, requiring careful planning of operations but not badly disrupting them. Crucial instruments will be turned off for short periods during close encounters with the radarsats themselves, and will be adjusted to avoid reporting gamma rays produced by electrons and positrons that the reactors emit. This will complicate mission planning but will reduce scientific returns only slightly. More reactors in orbit, however, would be bad news. Martin Marietta gets contract for the space station's Canadian Contribution Duplication, er excuse me Flight Telerobotic Servicer. MM's latest design is much more anthropomorphic than older designs, with a pair of video cameras with zoom lenses and spotlights in the "head" and a pair of arms attached to the "shoulders" of a roughly-rectangular equipment box. There is a third arm, located... um... where a tail would be but in front :-)... which will anchor the servicer to its work site. There will be a flight test in 1991, aimed mostly at human-factors assessment, and a full flight demonstration in 1993. SDI prepares to launch a neutral-particle-beam experiment on a sounding rocket. The main objective is to examine how the beam propagates away from the spacecraft and interacts with the near-spacecraft environment. The hope is to demonstrate that problems with NPB technology, formerly thought to make it impractical as a useful weapon, have been overcome. Letter from Michael Lang, commenting on an earlier expendables-are-best letter: "H.L. Anderton is apparently living in a dream world if he thinks we would be able to recover from an expendable launch failure in a month. Maybe he forgets that there have been long launch delays after every recent failure. The incidents all have one crucial thing in common with the recovery process after the Challenger failure -- bureaucrats. Every time we have a failure, it's not the engineers who determine the problems and solutions. A bunch of bureaucrats form advisory panels, testify endlessly in blue-ribbon, round-table discussions, and make technical decisions about systems they may not have seen in years (if ever). Meanwhile the technical people, who live and work with these systems every day, are forced to worry about layoffs and wait..." -- $10 million equals 18 PM | Henry Spencer at U of Toronto Zoology (Pentagon-Minutes). -Tom Neff | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
roy@phri.UUCP (Roy Smith) (07/02/89)
In <1989Jul2.054432.5054@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > the Atlantis crew replaced one of the orbiter's five general-purpose > computers after it failed [...] it took about four hours because the > computers are behind some of the middeck lockers and are not easy to get at. I don't understand. I thought that the various computers were all constantly checking each other and if one failed, it would be taken off line automatically and the others would continue to operate without it. Why the need to rummage around behind the furniture for 4 hours? -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 {allegra,philabs,cmcl2,rutgers,hombre}!phri!roy -or- roy@alanine.phri.nyu.edu "The connector is the network"
henry@utzoo.uucp (Henry Spencer) (07/03/89)
In article <3827@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >> the Atlantis crew replaced one of the orbiter's five general-purpose >> computers after it failed ... > > I don't understand. I thought that the various computers were all >constantly checking each other and if one failed, it would be taken off line >automatically and the others would continue to operate without it. Why the >need to rummage around behind the furniture for 4 hours? Almost certainly they could have completed the mission without doing so. However, having one computer dead *before* reentry means having that much less redundancy available against the possibility of further failures. So shuttle mission rules say that if time and parts are available, the repair will be done. If you were aboard, would *you* vote for reentering with one computer dead if you could avoid it? The real botch here is that the computers are so inaccessible that it takes four hours to replace one. -- $10 million equals 18 PM | Henry Spencer at U of Toronto Zoology (Pentagon-Minutes). -Tom Neff | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (07/04/89)
In article <1989Jul2.210944.15387@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > The real botch here is that the computers are so inaccessible that it takes > four hours to replace one. Sorry, I don't necessarily agree. As Henry obviously knows, design of something like a space shuttle is a series of tradeoffs. While accessbility of the computers for replacement is certainly important, so is accessiblity of other equipment, lockers, etc. The designers felt -- rightly, I'd say -- that in-orbit failure was a comparatively low probability, and chose not to optimize for such a situation. Given that this is the first time the replacement has been done, I'd have to agree with them. --Steve Bellovin
henry@utzoo.uucp (Henry Spencer) (07/04/89)
In article <11749@ulysses.homer.nj.att.com> smb@ulysses.homer.nj.att.com (Steven M. Bellovin) writes: >> The real botch here is that the computers are so inaccessible that it takes >> four hours to replace one. > >Sorry, I don't necessarily agree. As Henry obviously knows, design of >something like a space shuttle is a series of tradeoffs... Granted... but NASA has somewhat of a history of assuming that the hardware must work -- it says so in The Book, after all! -- and so it's unnecessary to set things up so the astronauts can fix it. I.e., while tradeoffs do happen, they can and do get skewed by institutional biases. -- $10 million equals 18 PM | Henry Spencer at U of Toronto Zoology (Pentagon-Minutes). -Tom Neff | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
rich@grebyn.com (Rich Kolker) (07/11/89)
In article <3827@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >In <1989Jul2.054432.5054@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >> the Atlantis crew replaced one of the orbiter's five general-purpose >> computers after it failed [...] it took about four hours because the >> computers are behind some of the middeck lockers and are not easy to get at. > > I don't understand. I thought that the various computers were all >constantly checking each other and if one failed, it would be taken off line >automatically and the others would continue to operate without it. Why the It's been a while since I've been on the net, but let me take a crack at this one. The GPC's are not taken off line automatically, In the case of a problems, there is a 5x5 grid above the commander's chair that shows GPC status. One axis is which computer is voting and the other is which computer the voting computer says is going bad (has gone bad). The GPC control switches are directly above the CDR's seat and are taken on/off line manually. Generally, only three are kept powered up during orbital flight although flight rules say all five are to be up, running and available for launch and entry. This from my feeble memory, although if something is really wrong, catch me and I'll go back to the manuals for the final say (I've got the 2102s for the GPC's around here somewhere). ++rich +-----------------------------------------------------------------------+ | Rich Kolker | | uunet!telenet!richk (not the reply to above) +-----------------------------------------------------------------------+