henry@utzoo.uucp (Henry Spencer) (07/18/88)
Well, I'm back from vacation and past my immediate software troubles, so here we go again. The next few summaries are going to be rather terse, in the interest of catching up. Editorial urging NASA to avoid unrealistic attempts at scheduling the next shuttle launch as early as possible, and in particular suggesting a need for reasonable contingency margins to cover the unexpected. "In practice, virtually every task has taken more time than scheduled." April 8 SRB test revealed crack in aft SRB skirt weld and a bolt failure at 1.32 times expected launch loads. The official margin is 1.4; it has been suggested that this is overly conservative, since launch loads are now well understood. Japan successfully tests prototype SRB for the H-2 launcher. Ford Aerospace is hitting technical problems on instrumentation for the next-generation Clarke-orbit metsats, causing cost overruns. Delays are considered unacceptable because the existing GOES satellites have limited lifetimes and time is short. SDI planning classified multi-experiment package for Delta launch in August; it will replace the Relay Mirror Experiment originally planned, which has hit technical problems. USAF will fully mothball the Vandenberg shuttle pad next year. Keeping it in standby is too expensive when the USAF no longer expects to use it. It will not be converted for Titan 4; a new facility will be built for that. Specialized shuttle equipment will go to KSC. US Army wants a heavylift launcher to provide assured access to space, says it "must be cheap and built by workers in a foundry, not technicians in a clean room". USAF still wants space-based radar, but has a problem affording it. NASA runs full-scale shuttle landing rehearsal at Edwards. Ariane launch with Intelsat 5 slips one week for inspection of the third-stage engine; loose pieces of insulation have been found in another such engine, probably from the engine test stand. Scout launches two Navy navsats from Vandenberg April 25. April 20 SRB test goes okay, boot ring survives. It now appears that one boot ring failed near the end of the SRB burn on mission 51J. The nature of the problem appears to be that vent holes connecting the motor cavity to the inside of the flexible boot tend to plug up as burnout approaches, and as pressure falls inside the motor the trapped high pressure inside the boot puts extra stress on the rings. Nozzle vectoring makes this worse. Instrument readings suggest that the boot ring failure in December occurred after burnout, during post-burnout vectoring done to calibrate actuator forces. The April test did slightly less vigorous vectoring during the burn (to the software limit, rather than the hardware limit), and did not do post-burnout vectoring (so that the boot ring could be inspected in its burnout state). There is disagreement about whether SDI's planned Boost Surveillance Tracking Satellite and Zenith Star space laser experiments comply with the ABM treaty. SAC suspects Soviets are developing major military space systems not known to intelligence analysts; Soviet launch capacities appear to exceed known requirements by a considerable margin. -- Anyone who buys Wisconsin cheese is| Henry Spencer at U of Toronto Zoology a traitor to mankind. --Pournelle |uunet!mnetor!utzoo! henry @zoo.toronto.edu