Richard Feynman, a theoretical physicist and Nobel laureate, picked up a piece of the O-ring material used in the rocket booster, pinched the ends of it together and dropped it into the cold water. When he pulled it out, it failed to regain its shape.
The accident, 73 seconds into the flight, killed teacher Christa McAuliffe and six astronauts.
The commission found two causes:
The commission, referred to as the Rogers Commission, after its chairman, former Secretary of State William P. Rogers, issued its report June 6, 1986.
Following are excerpts from Feynman's personal observations on the reliability of the shuttle, made in an appendix to the report:
It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher [probability - 1 in 100] figures come from the working engineers, and the very low figures from management.
What are the causes and consequences of this lack of agreement? Since 1 part in 100,000 would imply that one could put a Shuttle up each day for 300 years expecting to lose only one, we could properly ask "What is the cause of management's fantastic faith in the machinery?"
... A more reasonable figure for the mature rockets might be 1 in 50. With special care in the selection of parts and in inspection, a figure of below 1 in 100 might be achieved but 1 in 1,000 is probably not attainable with today's technology. ...
NASA officials argue that the figure is much lower.
... They point out that these figures are for unmanned rockets, but since the Shuttle is a manned vehicle "the probability of mission success is necessarily very close to 1.0."
It is not very clear what this phrase means. Does it mean it is close to 1 or that it ought to be close to 1? They go on to explain "Historically this extremely high degree of mission success has given rise to a difference in philosophy between manned space flight programs and unmanned programs; i.e., numerical probability usage versus engineering judgment." ...
... It would appear that, for whatever purpose, be it for internal or external consumption, the management of NASA exaggerates the reliability of its product, to the point of fantasy. ...
The phenomenon of accepting for flight, seals that had shown erosion and blow-by in previous flights, is very clear. The Challenger flight is an excellent example. There are several references to flights that had gone before. The acceptance and success of these flights is taken as evidence of safety.
But erosion and blow-by are not what the design expected. They are warnings that something is wrong. The equipment is not operating as expected, and therefore there is a danger that it can operate with even wider deviations in this unexpected and not thoroughly understood way. The fact that this danger did not lead to a catastrophe before is no guarantee that it will not the next time, unless it is completely understood.
When playing Russian roulette the fact that the first shot got off safely is little comfort for the next. The origin and consequences of the erosion and blow-by were not understood. They did not occur equally on all flights and all joints; sometimes more, and sometimes less. Why not sometime, when whatever conditions determined it were right, still more leading to catastrophe?