Thursday, January 28, 2016
The Challenger Disaster: What You Don't Know
The Challenger blows up thirty years ago over Cape Canaveral
It is safe to say that every sentient person alive 30 years ago recalls exactly where he or she was when informed of the news that the Challenger Space Shuttle had blown up. I was holding office hours for physics and space physics in the Physics Bldg. of the University Alaska-Fairbanks. A student had rushed through the door, barely coherent, and yelped: "The Space Shuttle just blew up!" Few could make sense of events from the assorted blurting so it was natural for people to find the neaarest television and turn to CNN as soon as time allowed.
As in the events of the Kennedy assassination, the horror and shock of the moment engulfed everything at the time. No sense could be made of the causes - only seeing the endless loop of disastrous imagery - that insane, peculiar Y-smoke plume engraved on an otherwise pristine sky over Florida.
The final answers wouldn't emerge until after the formation of an actual government commission (unlike the PR Warren Commission set up by LBJ to investigate the Kennedy assassination) and the stellar work of one bold physicist: Richard P. Feynman. It was, in fact, Feynman who conducted a simple ice water experiment before the Challenger commission to show it was none other than the failure of an obscure mechanical component (O-rings) in freezing temperatures that triggered the cataclysmic event.
Most of this is written up in over 135 pages of his book, 'What Do You Care What Other People Think: Further Adventures Of A Curious Character', 1989. What we learn is how Feynman painstakingly extracted the information to conduct his "little experiment" - as he called it - by pursuing points with the Thiokol engineers and other personnel. He learned, for example (pp. 134-35):
- There were images of hot gas leaks from previous flights - or what the engineers called "blowby"
This inevitably left a "blackening behind an O-ring where hot gas leaked through."
-In some instances, it left an "erosion" where the O ring had actually been burned by the gases a little bit.
-There were charts of all the flights showing how seriously the blowby and erosion manifested on each one.
Basically all these aspects were relevant as Feynman learned something else: During any given Shuttle launch there occur vibrations which cause the rocket joints to move a little. (Bear in mind the O-rings are directly attached to the solid rocket booster) The O-rings are placed inside the rocket joints and are intended to make a seal and - as Feynman learned - without the O-rings the solid booster's hot gases would expand through the joint and cause a catastrophic event.
On further discussions with the Morton Thiokol engineers, Feynman learned these O-rings had zero resilience at low temperatures. Having lost resilience, they'd be next to useless and then would not keep the crucial seal and so allow hot solid fuel booster gases to expand precipitously, He learned that on the morning of January 28th, 1986, temperatures had actually reached as low as 22F at the Cape, or 10 degrees below freezing.
It was time for his experiment!
Seated at one table he had asked an assistant staff member to bring him a glass of ice cold water (with ice actually in it to ensure it was at 32F). As Feynman describes his testimony, after switching on his microphone (p. 151):
"I took this rubber from the model and put it in a clamp in ice water for a while. I discovered that when you undo the clamp the rubber doesn't spring back. In other words, for more than a few seconds, there is no resilience in this particular material when it is at a temperature of 32 degrees. I believe that this has some significance for our problem."
And in typical, understated Feynman fashion, he blew the minds of the commissioners and others to smithereens. Showing with a simple physics experiment the central cause of the Challenger explosion: the Shuttle was rushed out for a launch in freezing temperatures, causing O-ring failure and the hot booster rocket gases to explode outward - claiming the lives of all eight astronauts on board, including teacher Christa MacCauliffe:
One narrative uncovered by Feynman, in the wake of his experiment, was that NASA wanted the Challenger launch made that icy morning, because it coincided with the date of Reagan's State of the Union speech. Then Reagan could tout the triumph, e.g. of space made even safe for school teachers, during his appearance on national TV. Instead he had to deliver a somber eulogy.
But Feynman's experimental exposure of NASA's callous neglect was so devastating and incriminating that the account would only find its way into an Appendix of the Proceedings.
Showing once again that too many humans can't handle the truth!