Feynman solves Challenger mystery

I know this is turning into a Feynman blog, but here’s a classic story:

Physicist Richard Feynman was reluctant to serve on the Presidential Rogers Commission to investigate the Challenger space shuttle disaster, but he complied, and it was a good thing he did. The goal of the 14-member Commission was simple: Find out what went wrong.

It doesn’t take Noble Prize winner to know that the best best place to start would be the place the shuttle was built, so off he went. The first thing Feynman found while talking to people at NASA, was a startling disconnect between engineers and management. Management claimed the probability of a launch failure was 1 in 100,000, but he knew this couldn’t be. He was, after all a mathematical genius. Feynman estimated the probability of failure to be more like 1 in 100, and to test his theory, he asked a bunch of NASA engineers to write down on a piece of paper what they thought it was. The result: Most engineers estimated the probability of failure to be very close to his original estimate.

He was not only disturbed by management’s illusion of safety, but by how they used these unrealistic estimates to convince a member of the public, teacher Christa McAuliffe, to join the crew, only to be killed along with the six others.

Feynman dug deeper, where he discovered a history of corner-cutting and bad science on the part of management. Management not only misunderstood the science, but he was tipped off by engineers at Morton Thiokol that they ignored it, most importantly when warned about a possible problem with an o-ring.

Feynman discovered that on the space shuttle’s solid fuel rocked boosters, an o-ring is used to prevent hot gas from escaping and damaging other parts. Concerns were raised by engineers that the o-ring may not properly expand with the rest of the hot booster parts, keeping its seal, when outside temperatures fall between 32 degrees Fahrenheit. Because temperatures had never been that low, and there had never been a launch failure, management ignored the engineers. The temperature on launch day was below 32 degrees.

Feynman had his answer, he just had to prove it.

The perfect opportunity arrived when he was requested to testify before Congress on his findings. With television cameras rolling, Feynman innocently questioned a NASA manager about the o-ring temperature issue. As the manager insisted that the o-rings would function properly even in extreme cold, Feynman took an o-ring sample he had obtained out of a cup of ice water in front of him. He then took the clamp off the o-ring which was being used to squish it flat. The o-ring remained flat, proving that in fact, resilliancy was lost with a temperature drop.

The last line of Feynman’s “Personal Observations on the Reliability of the Shuttle,” which was included as an appendix to the Rogers report was this:

“For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.”


~ by jack, dude on October 2, 2007.

One Response to “Feynman solves Challenger mystery”

  1. […] loosing their elasticity when exposed to cryogenic temperatures. For details of the case, check out these writeups. This was not necessarily a software failure but the investigations had spillover effects […]

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