On Sat, 30 Aug 2003 17:15:37 +0000, Doug wrote:

In article , n-
neckar.de says...


My asseration was about a small ball of ice inside the foam debris.
The seperation of the foam from the ET was probably associated with an
older crack (hours or days old). And in such a crack ice accumulation by
cryopumping is a possibility. Thats my line of thinking and I assume
that of Schomburg & Co. too. In such scenario more weight and therefore
more damage is obvious.

Lots and lots of us speculated about whether or not there was ice mixed
with the foam that hit the wing. With all of the talk and all the
analysis the CAIB did, I still haven't seen a really good theory proposed
for the *process* that resulted in the shedding of such a large chunk (or
chunks) of foam from the bipod ramp. It wouldn't surprise me in the
least if ice formation was involved.


The Gehman board seems to have ruled this out. On page 53 of the report we
find "despite commonly held perceptions, numerous tests show that moisture
absorption and ice formation in the foam appears negligible."

Also, in a manner reminiscent of Feynmans chilled O-ring material
experiments during the Roger's commission, but with quite different
results, another nobel prize Physicist Douglas Osheroff, did an experiment
which strongly contraindicates that either cryopumping or cryoingestion
could have been the root cause.

Cryopumping is a pressure increase which would have been caused if a crack
in the foam allowing air to penetrate the foam to near the tank surface
and liquefy and then expand as the propellant level falls. Cryoingestion
would be a similar effect caused by a liquid nitrogen leak from the tank
under the foam.

Osherhoff's experiments indicate that the hydrostatic pressure caused by
either of these effects would find a vertical escape through the foam, and
NOT cause the foam to de-laminate from the tank.

This is described on pp 53-54 of the report.

The board found that "Analysis of numerous separate variables indicated
taht none could be identified as the sole initiating factor of bipod foam
loss. The Board therefore concludes that a combination of several factors
resulted in teh bipod foam loss." F3.3-9