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SRBs, LESs, Ejection Seats & 100% Oxygen Atmosphere (split from SpaceX Discussion)


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6 hours ago, DDE said:

Wouldn’t it the loads be rather lightened because SRB thrust termination involves ejecting all of the unburnt fuel?

SRB thrust termination doesn't eject anything; it just blows the forward end of the motor open.

For something like the Shuttle stack, the SRBs would have had two explosive panels, one ventral and one dorsal. Thus the ejecta would miss the Shuttle and neither push it toward nor away. The "abort SRB" function, usable only from about 80 seconds to 120 seconds, would blow the panels and then jettison and fire the separation motors a split second later.

4 hours ago, DDE said:

Not what I’ve heard about Minuteman thrust termination. Apparently a blown-out nozzle would suck most of the contents out and snuff the rest.

It would snuff, yes, but that rubberized bombstuff isn't going anywhere.

 

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On 2/28/2019 at 6:57 PM, sevenperforce said:

So if the STS had been equipped with thrust termination on the boosters and that O-ring had lasted only a dozen seconds more, there would have been at least twenty seconds--fully a 6th of the booster burn time--during which a thrust shortfall could have triggered simultaneous booster shutdown and clean separation, with the SSMEs having just enough sustainer authority to keep the stack flying straight. It still would have been an abort, but it would have given them a chance.


o.0  What part of "the resulting transient shock loads would shred the ET" was too hard for you to grasp?  Millions of pounds of force simply don't disappear.


 

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11 hours ago, DerekL1963 said:


o.0  What part of "the resulting transient shock loads would shred the ET" was too hard for you to grasp?  Millions of pounds of force simply don't disappear.

Millions of pounds of force disappear at booster burnout, do they not?

STS boosters were jettisoned just as their thrust began to drop off, thus allowing residual thrust (and the separation motors) to carry them free. If they are jettisoned too early, their high remaining thrust would likely result in collision; jettison too late and the transient shock load would indeed shred the ET.

My point was that the stack does not yet have a TWR>1 at booster separation, but can still maintain heading via gimbal. If blow-out panels had been installed, then, the thrust could have been caused to drop off in the same way as typical burnout, permitting a "premature separation" with substantively the same forces as a nominal separation. Prior to T+80, this sort of separation definitely would have resulted in LOCV, as the stack would not yet have enough thrust to maintain heading, but between 80-85 and 120 seconds it could have been survivable.

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