[AR] Re: Columbia etc. (was Re: Valley Tech...)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 27 Mar 2020 18:14:42 -0400 (EDT)
On Fri, 27 Mar 2020, roxanna Mason wrote:
adding insult to injury, it was revealed afterwards that the newer foam
formula was an environmentally friendly type which had adhesion problems!.
But adhesion problems weren't involved -- see CAIB report section 3.2.
Very few of the foam losses went all the way down to the aluminum/primer
underneath -- the foam was *coming apart*, not peeling off the metal.
The "environmentally friendly" foam wasn't new on STS-107 -- in fact it
dated back to STS-84 -- and the changes had nothing to do with adhesion.
It was a change of blowing agent, from a CFC to an HCFC, and what it did
cause was pressure buildup and stress concentrations *within* the foam,
which increased shedding of outer parts of the foam. This was first
noticed on STS-87, and various detail changes reduced shedding over the
next nine flights until the shedding rate was back to "normal" (not zero,
just back to what it had been with the older foam), at which point the
problem was deemed solved. In any case, there were three different types
of foam used on the ET, and the chunk of foam that hit Columbia's wing
came from the "bipod ramp" area... and the type of foam applied there
still used the *old* blowing agent! So this change was TOTALLY IRRELEVANT
to the accident. [CAIB, ch. 6, "Other Foam/Debris Events" section.]
Henry
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