Lots written about the Challenger diasater on the 25h anniversary. I was reading the 1986 presidential report and came upon this:
Report of the Presidential Commission on the Space Shuttle Challenger Accident
(In compliance with Executive Order 12546 of February 3, 1986)
Chapter VI - An accident Rooted in History...................120
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.
The rest, as they say, is history.