[AR] Re: reusability and reliability (was Re: Re: Congratulations, Bill...)
- From: Henry Spencer <henry@xxxxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Tue, 1 Oct 2013 10:36:59 -0400 (EDT)
On Mon, 30 Sep 2013, George Herbert wrote:
> Reentry TPS could have failed on either, but the details of how it failed
> depended on reusable design.
Or alternatively, on a "reusable" having major expendable components that
could not be flight-tested, so debugging had to depend on making them
identical... which failed. (Up to and including the very last flight,
even after the post-Columbia fixes, ETs frequently lost substantial
chunks of foam from semi-random places.)
> SRB burnthrough... Unrelated to design mode, but prompted by the
> reusability (stuck with SRBs when budget failed to come through and size /
> performance specs were already committed, roughly).
I would say quite strongly related to design mode, as above -- debugging
was greatly hampered by the use of semi-expendable components. Each SRB
was a one-shot expendable assembly (with some reusable components) that
could not be flight-tested or even static-tested before flight. Even if
all SRBs had been identical, they were too expensive to expend the number
needed for a thorough test campaign.
Compare to the Saturn V, where engines for an expendable rocket were
required to be qualified for 20 starts and half an hour of operation --
numbers approximate, references aren't handy -- just so they could be
tested before their one and only flight.
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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