From stmx3:
Stuf4 wrote:
[snip]


I see it as a matter of confidence, as previously stated. I don't see
much significant change in the level of risk during that period. Nor
in NASA's perception of that risk.


[snip]

But don't say 12 flights is too conservative while 1 is not conservative
enough...risk does not decrease with each successful launch.


But our awareness of risk *does*. This was the warning from STS-112.
It shouted out that SOFI needed more attention. It got ignored.

Your statements appear contradictory. In the first, you imply NASA's
perception of the risk during the 12 flights following Challenger did
not change. In the 2nd, you say the awareness of the risk does change
over time. *THAT* was my earlier point...perhaps NASA became complacent
in assessing risk. Unless I am misreading you, you are not consistent
in your point of view.

To restate for clarity...

Our awareness of risk doesn't change much when nothing goes wrong, but
close calls *will* increase our awareness.

This is why confidence building is needed. You may think that you
have a handle on the risks, but empirical evidence can show you
otherwise.

*Confidence building* is almost as nebulous as *safety culture*. You
should have the confidence before you risk lives. NASA's problem is
that they became OVERCONFIDENT (not yelling, just emphasizing).
Overconfidence comes from a successful flight, seemingly justifying the
risks you've taken. 50 or more successful flights lead to a safety
culture that doesn't insist on conducting stringent tests since this
imposes a risk and budget and schedule and besides, "we have confidence
that puny foam isn't going to bring down America's finest feat of
engineering."

I see it more as a matter of cold probability, along these lines:

Q- "What are the odds that this foam shedding problem is going to hit
the orbiter?"

A- "We think that they are small and we are willing to take that
risk."

So I would agree with your assessment of overconfidence strictly from
this probability aspect.


I'm sure you've heard that the latest word from NASA (new since this
thread) is that STS-114 *will* be treated as a test mission, a
confidence builder if you will.

snip
Besides, there are worse ways to die.


(Ed Givens comes to mind.)

I take it he picked the leather upholstery over the antilock brakes.

Ha.


~ CT