http://www.usspacenews.com/rumbelings.html

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The ET Saga

Several years ago (in the 90's) the EPA and a past Administrator
demanded the shuttle program remove Freon from the primary ET
foam (CPR-488). From the moment NASA implemented the change,
lots of foam was flying off the ET. Now we had a new problem.

Thought is now being given to going back to the old CPR-488 foam.


ET Hints From MSFC

Inside word from MSFC is the largest piece of foam that came off
Discovery's ET is the result of work conducted in the forward end of
the area that failed and may not be an issue requiring redesign.

Revised maintenance and close out standards may take care of the
risk.

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"The largest piece of foam," eh? Got a photo of it?

Challenger's Ghost