Re: Thoughts on VSE Launch Vehicles

gherbert@xxxxxxxxx (George William Herbert) wrote in news:11dbu4b2g1i90e8
@corp.supernews.com:

>
> What are the real odds? There isn't enough info to establish
> the risk definitively. I would say, as a reasonable outer bound,
> no further out than 1/1000. And possibly much closer to 1/250.
> Historical evidence is that no SRB program has proven immune to
> nasty suprises, and the total catastrophic loss rate of large SRBs
> (segmented or not) is statistically significant. Even if we
> grant that RSRM is a good SRB, it's still a SRB, and CATOs
> remain within the predicted future risk envelope for SRBs.
> Period.
>

Pretty thought-provoking post -- thanks...

A couple of questions come to mind...

(1) Has a timeline ever been published for any of the Titan III/IV SRM
incidents? I've seen video of the Vandenburg explosion and although it
seems instantaneous, I'm sure it took a finite amount of time to go from
initiation to fireball. Assuming a similar time for the SRB would give
some kind of lower bound on how quickly any crew escape system would need
to react... assuming a sensor could detect the onset of the problem
(pressure sensor, break wires in the case, etc).

(2) Although there hasn't been much incentive in the past, has there been
any effort to develop an SRM with "blow-out panels" or something similar
to moderate the severity of an incident? It would obviously need to work
in a range that provided a reasonable margin over the normal operating
pressures (plus any normal transients), but "opened" at something less
than the case failure pressure. I imagine, however, that the propellant
is going to distribute the internal pressure in an upset over a wider
area of the case wall than if it were a less rubbery material, so the
panels would be difficult to design and would require some significant
testing.

> Is 1/1000 an acceptable risk? Is 1/250 an acceptable risk?
> These are separate questions. I think most astronauts will
> feel that they're in a reasonable ballpark (STS is still
> worse than those). Future commercial astronauts may not agree.
> Those are separate questions, though, from assessing the risk
> of CATO.
>

An optimist would point out that the Stick would at least reduce the
*existing* risk of a catastrophic SRB failure by half over that of the
Shuttle -- and possibly by a little more since (as someone pointed out
earlier) you're eliminating the "twang" that the Shuttle SRB undergoes
today.

--
I was punching a text message into my | Reed Snellenberger
phone yesterday and thought, "they need | GPG KeyID: 5A978843
to make a phone that you can just talk | rsnellenberger
into." Major Thomb | -at-houston.rr.com

.

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