iiit-sh@cybaswan.UUCP (Steve Hosgood) (09/08/88)
We've seen one way that a shuttle can be lost :-(.
Is there any way to prevent the following possible failure modes resulting
in another such loss?
1) Not all the explosive bolts holding the stack to the pad blow. Assuming
worst case, if all bolts on one side held firm after the Solid Rocket
Boosters ignite, you'd have a force in the region of 2.9 Million
pounds acting to twist the stack around the fixed point, which I
suspect could easily throw the whole lot into the deck next to the
pad. Assuming the External Tank would rupture, the resulting
explosion would probably level every structure at KSC for miles.
(In practice the rogue explosive bolts would probably snap before
that point, which would cause the vehicle to launch off-vertical.
Can that be corrected-for?)
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? Can the pad take that sort of blasting? Can the external tank
remain cool enough to avoid risk when it's sat next to an SRB at
full bore without the airflow to cool it?
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.. Are these
figures right? (Within +/- 50% I mean :-))
Sorry to be raising such gloomy points, but it's worth noting that Gen. Chuck
Yeager owes his life to such discussions of doom. Someone once asked "what
would happen if you drop in the X-1 from the carrier aircraft and find you
have a total power failure? You can't fire the rockets and end up doing a
dead-stick landing with a full load of fuel onboard that can't be dumped.
The undercarriage'll never take the strain." As a result they fitted a manual
fuel dump valve. It was needed in earnest soon afterwards. Read Yeager's book
(called "Yeager") for details. I quite enjoyed it.
BTW, I was glad to see the Soviets managed to sort out their problem in
returning those Cosmonauts from Mir. 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? (Followups on this last point to
sci.space please).
-----------------------------------------------+------------------------------
Steve Hosgood BSc, | Phone (+44) 792 295213
Image Processing and Systems Engineer, | Fax (+44) 792 295532
Institute for Industrial Information Techology,| Telex 48149
Innovation Centre, University of Wales, +------+ JANET: iiit-sh@uk.ac.swan.pyr
Swansea SA2 8PP | UUCP: ..!ukc!cybaswan.UUCP!iiit-sh
----------------------------------------+-------------------------------------
My views are not necessarily those of my employers!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)