The cover story is "Nuclear Propulsion for Space Travel". Large story on NASA Lewis's nuclear-thermal propulsion work, which is pushing for use of such engines in lunar missions in 2000-2005. Among the advantages being cited are finding out early whether the political problems can be overcome sufficiently to make nuclear propulsion viable for a Mars mission. Other points in favor are PR advantages of being less obviously a repeat of Apollo and early involvement of DoD and DoE in both work and funding. Details of proposed missions, some of which require a heavylift launcher.
Atlantis deploys early-warning satellite, crew proceeds to their secondary mission of evaluating manned military reconnaissance from orbit. The satellite will be the only warning satellite launched by shuttle; it is a leftover from the days when the shuttle was going to be the only launcher [although it's not clear whether it is a leftover for technical reasons -- incompatibility with expendable launch -- or bureaucratic ones that insist that the shuttle-compatibility effort have some tangible result]. Another secondary mission is assessment of free-fall effects on the pilot's ability to land the orbiter, a matter of considerable concern for the extended-duration missions now being planned. (Next year there will also be a test of the shuttle's theoretical capability to fly a fully automatic landing.) Also of note was a phenomenon not seen before, pulses of light dancing on the orbiter's nose between Mach 11 and cutoff.
The Atlantis launch Nov 24 was delayed five days by payload problems, and various problems were overcome during launch preparations. The left SRB was recovered damaged, and work is underway to establish whether (as hoped) this was the result of the water landing rather than earlier problems. KSC crews are bracing for an attempt to fly twelve shuttle missions in the next 14 months. Endeavour is about to join the operation fleet and Columbia is rejoining it. Atlantis and Discovery will be off flight status for a few months for refurbishing.
A group within NASA proposed offering the Soviets a penetrator for their Mars 94 mission, but it was rejected within NASA as "too risky"; when asked whether this meant technical or political risk, Griffin said "all of the above". Griffin is now hoping to use one or more of the Atlas 1 launchers that NASA has in inventory for the (delayed) GOES-Next program for lunar missions instead. He says it will be several months before firm decisions are made, but the current idea is four missions -- three orbiters and one lander -- within the next four years, each in the $100M class due to limited objectives and fast schedule. The orbiter missions would be for remote sensing. The lander would carry a small payload for either science or technology demonstration. One lander concept is a standardized design called Artemis (Apollo's sister) that could carry a wide range of 100-200kg payloads using simple off-the-shelf hardware. Griffin comments: "You can buy these by the yard and do that well into the next century... It will be a long time before we can afford to send men everywhere on the Moon." There are also potential uses in conjunction with manned operations, e.g. emergency resupply.
JPL readies Topex/Poseidon hardware for July launch. It is noteworthy in being the first NASA payload to use a non-US launcher (Ariane). It carries a variety of experiments, mostly ocean-related. One of note is a GPS receiver for early experiments on using GPS to track satellites. The bad news is that Topex/Poseidon is badly over budget, although it has now been agreed between NASA and Fairchild (the contractor) that a lot of it is NASA's fault: NASA raised the specs for both electronics and solar arrays midway through. Fairchild also is not used to the way JPL overbuilds spacecraft, e.g. with wider temperature margins than commercial spacecraft, and decided to deliver on time despite the problems, which meant paying a premium for fast results from suppliers.
Competition for the next generation of missile-warning satellites will have one unusual omission: the TRW/Aerojet team that builds the current ones will split. TRW has teamed with Grumman to get Grumman's advanced sensor technology developed for SDI, having decided that the USAF is likely to demand a major jump in capabilities that could not be met by upgrading the existing design. TRW and Aerojet are still under contract for the last batch of the existing birds, and there may be one more batch as a transition move.
JSC tests GPS as a replacement for the shuttle's current automatic landing system. Early results, using the shuttle training aircraft for tests, say that it's good enough horizontally but not vertically. Adding differential GPS and a radar altimeter helps.
Various groups have been comparing GPS to Glonass. At the moment they complement each other somewhat: GPS coverage is better at the equator, Glonass at the poles. Glonass accuracy is comparable to GPS if GPS's accuracy-degrading "selective availability" is switched off, and a good deal better when selective availability is on. Soviet authorities have stated that Glonass accuracy will not be deliberately degraded by any equivalent of selective availability. Canadian Marconi has development underway on a commercial receiver that will pick up both GPS and Glonass, with delivery possible in summer 1993 if enough interest appears.
Ohio U tries something different: doing accurate attitude sensing by comparing GPS signal phase at multiple antennas on the same aircraft. Some problems have been found, but already it looks very promising, with accuracies within 1 milliradian possible with a 1m baseline.
White House pledges funding for Landsat 7 in FY1993 budget request. Truly and Andrews (asst sec DoD for CCCI) outline Landsat plans; so far the only improvement over Landsat 6 planned for Landsat 7 is a TDRS antenna to permit continuous data transmission.
The X Window system is not layered, and | Henry Spencer @ U of Toronto Zoology it was not designed. -Shane P. McCarron | henry@zoo.toronto.edu utzoo!henry