henry@zoo.toronto.edu (Henry Spencer) (03/11/91)
Amroc proposes Aquila, a four-stage hybrid launcher for Motorola's Iridium mini-comsat network, claiming 1500lbs to 300nmi at about half the cost of current alternatives. ESA declares Ulysses fully operational. Space insurance rates expected to rise after circa $200M losses on recent in-orbit satellite failures. USAF Space Command has set up special data links to get data from missile- warning satellites directly to Patriot batteries nearly in real time. This plus other measures to improve communications have boosted warning time for Scud attacks to nearly 5min from 90-120s. Warning-satellite officials say Iraq's Scud tests late last fall were serious blunders, because they gave the US a priceless opportunity to debug the warning setup before it was needed in combat. Final design details have been settled for the field joint of the ASRM. The new joints are bolted together, the O-rings remain visible as the joint is mated, and the joint is designed to close up under pressure rather than opening. Looking at the diagram, inboard of the bolts the joint is two flat flanges touching each other, and two O-rings are set into the surface of the lower flange near the inner edge. The upper flange goes to the edge of the lower flange and then turns downward around it, with a third O-ring set into the outer surface of this lip, seating against the inner edge of the lower flange. Another major ASRM design change is careful design of the internal shape of the fuel so that thrust drops off somewhat for a brief period early in the flight, eliminating the need for the SSMEs to throttle back during the period of maximum dynamic pressure. This eliminates assorted possible failure modes related to throttle-back and the following throttle-up. Other changes include a revised casing design that has fewer assembled parts, one less field joint, welded factory joints, and better steel; a simpler nozzle design eliminating assorted joints and seals; and a redesigned igniter. Finally, a lighter casing, a larger diameter holding more fuel, and a slightly more energetic fuel give higher thrust, longer burn, and about 18% more shuttle payload. An important change unrelated to the booster design is the shift to highly automated manufacturing, since each handling step increases the odds of trouble. [Another aspect of this, not mentioned, is that the ASRM plant at Yellow Creek will be NASA-owned, so NASA will be less tied to a single contractor and can exert more control.] ASRM still has its critics, however. Some say the $971M would be better spent elsewhere, especially on the SSMEs and on incremental improvements to the existing boosters (since ASRM is still five years away). There is the possibility of political pressure to shift money to heavylift boosters, and concerns about the environmental effects of the rather "dirty" solid fuels. Finally, there is still strong skepticism in some areas about the safety of manned flight on solid boosters, given the sensitivity to manufacturing flaws and the impossibility of test-firing. Cost considerations are likely to preclude abandoning SRBs, however. [That's it for space news in this AW&ST. They are rather preoccupied with other current events... However, here's a *very* interesting bit from the 15 Feb issue of Science:] Congress is very interested in the Augustine commission's recommendation for a heavylift launcher, and there is starting to be specific interest in one particularly heavylift launcher... the Saturn V!! Truly, questioned about the matter, says the plans still exist. It's pretty obvious, though, that NASA would really prefer a shuttle-derived launcher. Congress may pursue the matter, although there is the obvious problem that tooling is gone and many subcontractors are gone, so resurrecting the Saturn V would be costly. -- "But this *is* the simplified version | Henry Spencer @ U of Toronto Zoology for the general public." -S. Harris | henry@zoo.toronto.edu utzoo!henry