Author Topic: Challenger - Cold or Leak Checks?  (Read 1179 times)

Offline brad2007a

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Challenger - Cold or Leak Checks?
« on: 04/16/2009 05:05 PM »
I bought and watched the Spacecraft Films documentary DVD set "Challenger" recently, and something on the set raised a question for me that I was hoping someone here could answer.

On disc 1, there is a timeline about the history of the field joint problem that lead to the disaster. The commonly believed theory is (I think, correct me if wrong) that the cold weather froze the o-rings, rendering them incapable of sealing the aft/aft center joint on the right SRB. Of course, this is obvious, given all of the factors involved.

However, in this timeline it's pointed out that during the period leading up to the disaster, after almost every launch with an o-ring problem, the leak check pressure was increased. Subsequently, every time the pressure for these tests were increased, the problems got worse.

So my question is: which was the bigger problem in the end: the cold, or the leak check?

Obviously, I realize the biggest problem was the design of the field joint itself.

In answering, please remember - I'm not an engineer, just an intensely interested outsider. So please be gentle.... ;)

« Last Edit: 04/16/2009 05:06 PM by brad2007a »
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Offline Jim

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Re: Challenger - Cold or Leak Checks?
« Reply #1 on: 04/16/2009 05:10 PM »
cold

Offline Herb Schaltegger

Re: Challenger - Cold or Leak Checks?
« Reply #2 on: 04/16/2009 05:27 PM »
It's been a long time since I read the Rogers Commission report itself, but I believe it was determined that the leak check procedures, by increasing the pressures used for the test, were actually forcing the putty away from the from joint.  Combined with all other factors, especially the combination of the joint design and the cold weather behavior of the O-ring materials, this was a Very Bad Thing™. 

However, I still maintain that the original design of the field joint itself was the primary driver, temperature or not.  By allowing any hot combustion products at all to escape past the first O-ring at all, it was not behaving as expected, nor was the severity of the issue properly appreciated by people in the program.
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