henry@zoo.toronto.edu (Henry Spencer) (12/17/90)
[This is the last AW&ST summary for the next 2-3 weeks, as I will be on vacation. The good news, though, is that I'm actually caught up even so, since I consider a month behind to be normal.] Hydrogen turbopump of Pratt&Whitney's alternate SSME pump assembly runs successfully at 100% power. P&W has a contract to demonstrate an alternative to the current (Rocketdyne) pumps, up to and including flight certification in 1993. [There are, however, no specific plans to actually fly the new pumps, or to convert the shuttle fleet to use them, even if they work well.] P&W is about to deliver its first pump set to Stennis for tests. The X-30 overall color scheme will be white for first flight, but once the program starts on higher Mach numbers, it will probably revert to the natural surface colors. No current paints are considered capable of surviving on the hotter sections. Pictures of the first Titan 4 version of the Centaur -- essentially the Centaur G-prime originally meant for the shuttle -- about to be shipped to the Cape in preparation for use on a military payload next year. GD has a $1.3G contract for 15 over the next five years. The new version is fatter than the old Centaurs and carries about 50% more fuel. Further improvements are being pursued. Modernized electronics will be more reliable and will cut electronics parts count and weight by about 50%. GD is also scheming a single-engine Centaur to reduce overall weight substantially, since the Titan application does not need the higher thrust of the current pair of engines. [Aha, I told you so!] NASA wants to postpone the Spacelab J shuttle mission to 1992, giving other [US!] payloads the last one or two slots in the reduced shuttle manifest for 1991. Japan, naturally, wants to fly its mission as planned. Magellan images, in quantity. The geologists are jumping up and down. The current big mystery is that crater counts make the surface relatively young, about 400Myr, while it is clear that there is very little erosion, with successive features superimposed on each other with all details preserved. (Earth's land surface averages 1Gyr.) The current guess is that the resurfacing is due to lava flows, which are quite prominent. It is not clear whether vulcanism is still occurring, although Magellan images may eventually resolve this. Another surprise is that the impact craters seem to be mostly the same age, while the Moon and other bodies show a wide range of ages. Minor problems for Magellan on the horizon: around April, thermal stresses will be at their peak, when the electronics sections are getting more or less continuous sunlight rather than being shaded by the antenna. This is an issue because Magellan's ability to reject heat is not up to spec, perhaps due to problems with its thermal blankets. Engineers are studying ways to reduce heat load, possibly by shortening the hot data-playback phase of each orbit -- this would limit mapping, but the hoped-for extended mission could cover missed areas. Hubble mirror board reports, blaming faulty test equipment, lack of proper management supervision, and inadequate expertise at and oversight by NASA. The board says NASA is half to blame, a view that "some high NASA officials" are not at all happy about. A possible contributing factor is that the project was being overseen by Marshall, during its worst pre-Challenger phase of discouraging reports of problems. The PE optical division successfully held off attempts to get either contractor or NASA personnel in to assess mirror fabrication operations. The ultimate problem was a fabrication error in the reflective null corrector, used in mirror testing. PE planned to certify the RNC with great care and avoid any need for independent testing of the mirror... but the board could not find any documentation that the RNC *was* properly certified, and criticizes PE for not planning independent tests. The probable problem in the RNC was that a measurement was done on the wrong part. It was supposed to be done on the end of a rod, visible through a hole in an end cap, but in fact a small piece of nonreflective coating had broken off the cap, and it seems likely that the measurement was actually done on the shiny spot on the cap instead. The board says that PE missed at least three chances to catch the problem. First, spacing washers had to be added to the rod to make it line up; "that in itself should have alerted people that something was different than designers had intended". Then, two other devices -- an inverse null corrector and a refractive null corrector -- were also used to check the mirror, and both indicated problems. However, PE engineers decided that the RNC was a certified test device and the inherently lower precision of the two other devices invalidated their results. A later request from an advisory body for an independent test for gross flaws was rejected because PE was confident that the earlier tests were right. Adding to the problem were managerial flaws. PE's own management did not supervise the Optical Operations Division properly. NASA project management lacked the expertise to evaluate the optical work. PE's best people were not involved in the Hubble mirror at all. NASA did not take the initiative to examine the fabrication process. And the NASA/USgovt review and QA process was adequate for issues like safety and handling but inadequate for optical quality. The Hubble backup mirror by Kodak, currently in storage, is essentially perfect. Hubble board, requested by NASA to review the Hughes Danbury (nee Perkin- Elmer) work on the mirrors for AXAF, gives it a clean bill of health. Communications with management have improved greatly, and QA and review people involved are on the ball this time. Hubble image of Saturn, showing the huge white storm in the planet's equatorial region, now planetwide. Despite the mirror problems, the Hubble image is 3-10 times better than Earth-based ones, and at least 400 images of the storm are planned. Soviets launch Gorizont comsat for internal use... not by the whole USSR, but on contract to the Russian Soviet Federated Republic, a first. Tenth operational Navstar launched by a new Delta version. This Delta has new lightweight strap-ons from Hercules, replacing the old Thiokol ones, and a higher-expansion nozzle on the main engine. Letter from Cathleen S. Lewis of the National Air and Space Museum, questioning AW&ST's calculations of the size of the Soviet space budget. She says that the ruble-dollar exchange rate AW&ST assumed -- 0.56R/$ -- is no longer even the USSR official rate. The official rate is now 1.80R/$ for commercial use and 5.90R/$ for tourism [!], and the black- market rate, which economists consider by far the most realistic, is 20-40R/$. At the lowest black-market rate, the annual operating budget of the Soviet space program is circa $325M, about the budget of the Smithsonian! -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry