henry@utzoo.uucp (Henry Spencer) (09/11/88)
In article <73@cybaswan.UUCP> iiit-sh@cybaswan.UUCP (Steve Hosgood) writes: >2) What happens if one of the SRBs doesn't light up? I assume the launch > sequencer doesn't blow the bolts, kills the liquid fuelled engines > and attempts to hold the stack on the ground until the one SRB goes > out? ... No, the bolts blow at the same instant as SRB ignition -- there is no delay to see if the SRBs have ignited properly. (I made this mistake once.) Seriously asymmetric SRB performance, with the worst case being ignition failure in one of them, is an unsurvivable accident. >3) What happens if the liquid fuelled engines flame out just after lift-off? > This is probably the least dangerous problem, the 2 SRBs I believe > provide about 5.8 Million Pounds force between them, and the 3 liquids > supply "only" about another million between them. The shuttle may not > get into orbit, but at least it should have a chance of attaining > about 15-20 miles altitude, which ought to be fairly safe... I don't remember for sure, but I think the end result of a failure like this is more-or-less normal flight up to SRB jettison, followed by immediate ET jettison, followed by either an emergency landing or ditching in the ocean. This assumes that there are no major control problems at SRB burnout, given that the liquid engines can't be used to compensate for asymmetric burnout. >[Soviets] I wonder why they jettison the docking >module before tring to fire the retro rockets to commence re-entry? Surely >there would be time enough afterwards? ... Probably they don't want the docking module wandering around uncontrolled nearby during reentry. Also, the less mass is on board at retrofire time, the smaller and lighter the retros can be. -- NASA is into artificial | Henry Spencer at U of Toronto Zoology stupidity. - Jerry Pournelle | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
masticol@paul.rutgers.edu (Steve Masticola) (09/11/88)
Henry Spencer := >, Steve Hosgood := >> > >[Soviets] I wonder why they jettison the docking > >module before tring to fire the retro rockets to commence re-entry? Surely > >there would be time enough afterwards? ... > Probably they don't want the docking module wandering around uncontrolled > nearby during reentry. Also, the less mass is on board at retrofire time, > the smaller and lighter the retros can be. A third good reason is that if they've started re-entry and something goes wrong with jettisoning the docking module, they'd have very little time to fix the problem. Even if everything went right, they'd still cost themselves time when they had very little to spare. Jettisoning the docking module simplifies things all around. I'd hope they don't throw it so far away that they can't get back to it if something goes wrong with re-entry... - Steve (masticol@paul.rutgers.edu)