Re: An urban legend regarding documentation?
I have a question about the Challenger disaster, regarding its documentation.http://www.google.com/search?sourceid=navclient&q=Challenger+O%2Dring+documentation+warning
The key material is to be found in the Commission's report, one of the items
to which Bonnie's Google search points. The big problem was not whether the
warning was in some documentation, somewhere, but rather in the standards
(or lack of them) that were applied to the flights. The immediate problem
that brought down the Challanger was lack of resilency in the O-rings at
reduced temperature. (At launch it was 15 degrees F colder than any previous
launch.) Below is a quote of the key material. "Commissioner Feynman" who
is quoted in the Report is indeed the late CalTech physics professor Richard
P. Feynman, and it was his persistance and experimentation that found the
O-ring answer. He also determined that the liquid-fuel main engines had
standards as poor as those for the solid-fuel boosters.
If the item in question were actually included in the documentation, no one
would have changed any action based upon its presence.
<quote>
AN ACCIDENT ROOTED IN HISTORY
EARLY DESIGN
The Space Shuttle's Solid Rocket Booster problem began with the faulty
design of its joint and increased as both NASA and contractor
management first failed to recognize it as a problem, then failed to
fix it and finally treated it as an acceptable flight risk.
Morton Thiokol, Inc., the contractor, did not accept the implication
of tests early in the program that the design had a serious and
unanticipated flaw. NASA did not accept the judgment of its engineers
that the design was unacceptable, and as the joint problems grew in
number and severity NASA minimized them in management briefings and
reports. Thiokol's stated position was that "the condition is not
desirable but is acceptable."
Neither Thiokol nor NASA expected the rubber O-rings sealing the
joints to be touched by hot gases of motor ignition, much less to be
partially burned. However, as tests and then flights confirmed damage
to the sealing rings, the reaction by both NASA and Thiokol was to
increase the amount of damage considered "acceptable." At no time did
management either recommend a redesign of the joint or call for the
Shuttle's grounding until the problem was solved.
FINDINGS
The genesis of the Challenger accident -- the failure of the joint of
the right Solid Rocket Motor -- began with decisions made in the
design of the joint and in the failure by both Thiokol and NASA's
Solid Rocket Booster project office to understand and respond to facts
obtained during testing.
The Commission has concluded that neither Thiokol nor NASA responded
adequately to internal warnings about the faulty seal design.
Furthermore, Thiokol and NASA did not make a timely attempt to develop
and verify a new seal after the initial design was shown to be
deficient. Neither organization developed a solution to the
unexpected occurrences of O-ring erosion and blow-by even though this
problem was experienced frequently during the Shuttle flight history.
Instead, Thiokol and NASA management came to accept erosion and
blow-by as unavoidable and an acceptable flight risk. Specifically,
the Commission has found that:
1. The joint test and certification program was inadequate. There
was no requirement to configure the qualifications test motor as it
would be in flight, and the motors were static tested in a horizontal
position, not in the vertical flight position.
2. Prior to the accident, neither NASA nor Thiokol fully understood
the mechanism by which the joint sealing action took place.
3. NASA and Thiokol accepted escalating risk apparently because they
"got away with it last time." As Commissioner Feynman observed, the
decision making was:
"a kind of Russian roulette. ... (The Shuttle) flies (with O-ring
erosion) and nothing happens. Then it is suggested, therefore, that
the risk is no longer so high for the next flights. We can lower our
standards a little bit because we got away with it last time. ... You
got away with it, but it shouldn't be done over and over again like
that."
4. NASA's system for tracking anomalies for Flight Readiness Reviews
failed in that, despite a history of persistent O-ring erosion and
blow-by, flight was still permitted. It failed again in the strange
sequence of six consecutive launch constraint waivers prior to 51-L,
permitting it to fly without any record of a waiver, or even of an
explicit constraint. Tracking and continuing only anomalies that are
"outside the data base" of prior flight allowed major problems to be
removed from and lost by the reporting system.
5. The O-ring erosion history presented to Level I at NASA
Headquarters in August 1985 was sufficiently detailed to require
corrective action prior to the next flight.
6. A careful analysis of the flight history of O-ring performance
would have revealed the correlation of O-ring damage and low
temperature. Neither NASA nor Thiokol carried out such an analysis;
consequently, they were unprepared to properly evaluate the risks of
launching the 51-L mission in conditions more extreme than they had
encountered before.
</quote>
It is well worth reading the entire report, which is at
http://www.chron.com/content/interactive/special/challenger/docs/report.html
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References:
An urban legend regarding documentation?: From: Gilda Spitz
Re: An urban legend regarding documentation?: From: Bonnie Granat
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