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Old June 19th 06, 02:42 AM posted to sci.space.station
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Default "Managers" cleared the shuttle???

Jim Kingdon wrote in
news
Nasa managers cleared the shuttle for lift-off even though the
agency's top safety officer and its lead engineer objected,
officials said on Saturday.


There's a more detailed account at
http://spaceflightnow.com/shuttle/sts121/060617july1/
including some lengthy quotes from Griffin.

I would say that Griffin is guilty of some sloppy and wishful
thinking. For example, saying "I believe that our models are quite
conservative" (which is not reassuring unless you know something about
how conservative) or "we have 113 flights (sic) with this vehicle with
these ice-frost ramps under our belt" (we got away with it until now,
so it must not be a problem).


I suppose you could say that, but you'd be misquoting Griffin. He never
said or even implied that the IFRs "must not be a problem" - just that it's
not as *big* a problem as the word "probable" means in NASA's risk matrix.
NASA defines "probable" as "expected over the life of the program", in
other words, P 0.5 over the remaining 16-19 flights. Regardless of just
*how* conservative the models are, that can't even be close - if it were,
there simply shouldn't be any orbiters left by now, since P 0.5 over 16-
19 flights equates to 3 hull losses over 114 flights.

I also would say there is something positive in Griffin's comments,
and that is accepting that there is risk. At some level, people in
the shuttle program have always known that there is risk (much greater
than, say, flying in a commercial or general aviation aircraft), but I
don't recall it being acknowledged as openly or publicly as this
before.


I agree - and that's another data point that says he's not saying that the
IFR's "must not be a problem."

--
JRF

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