Vignette 9: O-ring in ice water
On the morning of February 11th, 1986, at a meeting of the Presidential Commission investigating the loss of space shuttle Challenger in Washington DC, Professor Richard P. Feynman obtained a piece of o-ring that had been provided to the commission by Morton-Thiokol, the makers of the solid rocket boosters used to launch the shuttle. Compressing the o-ring with a clamp he had purchased at a hardware store, he then dropped the clamped o-ring into a glass of ice water. As the o-ring chilled, Feynman questioned a representative of Morton-Thiokol about the reasons that rubber o-rings had been chosen for the purpose of sealing out hot gasses, with emphasis on the assumed resiliancy of the rubber.
Feynman then took the clamp off the o-ring and showed that the cold rubber remained compressed. This vividly demonstrated the cause of the failure. His famous words, "I believe that has some significance for our problem," were caught on camera by all the news agencies present.
At the time Feynman was terminally ill with stomach cancer. When asked to join the commission in January he had considered declining, but his wife Gwynneth talked him into accepting because she felt that he'd bring much needed outside expertise to the investigation. When he accepted he threw himself completely into the problem, studying everything he could get his hands on. He quickly learned that NASA management had engaged itself in an elaborate statistical exercise to convince themselves that the probability of a failure was much lower than it really was. Feynman's independent calculations led him to conclude that NASA faced a realistic probability of one catastrophic mishap in 72 flights.
When the Commission released its final report in May of 1986, it included an Appendix written by Feynman. This appendix explains the problems Feynman identified in his examination of the shuttle program, including a number of likely failure modes that could bring down future shuttle missions. It concludes with this thought, "Reality must take precedence over public relations, for nature cannot be fooled."
Two years later, on February 15th 1988, Richard Feynman died.
You can view a dramatic recreation of the event here. Video of Feynman at the conference compressing the o-ring is here. Feynman's appendix to the Commission report is here.
Feynman then took the clamp off the o-ring and showed that the cold rubber remained compressed. This vividly demonstrated the cause of the failure. His famous words, "I believe that has some significance for our problem," were caught on camera by all the news agencies present.
At the time Feynman was terminally ill with stomach cancer. When asked to join the commission in January he had considered declining, but his wife Gwynneth talked him into accepting because she felt that he'd bring much needed outside expertise to the investigation. When he accepted he threw himself completely into the problem, studying everything he could get his hands on. He quickly learned that NASA management had engaged itself in an elaborate statistical exercise to convince themselves that the probability of a failure was much lower than it really was. Feynman's independent calculations led him to conclude that NASA faced a realistic probability of one catastrophic mishap in 72 flights.
When the Commission released its final report in May of 1986, it included an Appendix written by Feynman. This appendix explains the problems Feynman identified in his examination of the shuttle program, including a number of likely failure modes that could bring down future shuttle missions. It concludes with this thought, "Reality must take precedence over public relations, for nature cannot be fooled."
Two years later, on February 15th 1988, Richard Feynman died.
You can view a dramatic recreation of the event here. Video of Feynman at the conference compressing the o-ring is here. Feynman's appendix to the Commission report is here.