But the change to CFC-free foams did not have an impact (heh) on Columbia. A CFC-free foam (NCFI 24-124 foam, blown with HCFC 141b) was used to cover the large expanses of flat acreage about the tank in an automated process, but this foam was not involved in the accident.
The piece that pierced the shuttle’s wing broke off the left bipod ramp of the external tank. This area was hand sprayed by experienced technicians, but used a different formulation, called BX250. This material is blown using Freon-11, as it has been since the beginning of the shuttle program.
Cite: Section 11 of the Working Summary of the Columbia Accident Investigation Board (34 MB PDF)
There isn’t any foam on the far side of the tank. The foam is there to insulate the pylons that attach the shuttle to the tank, to keep the fuel flowing into the shuttle from freezing.
When I first read the thread title, I thought this was going to be a suggestion for an alternative to landing the shuttle…catch it in some enormous net.
You sure about that? IIRC, the entire outside surface of the external tank is insulated, not just the pylons. It was foam from near the pylons that broke off on Columbia, but that’s not the only foam.
Yes, it would add weight. They stopped painting the fuel tank after someone (a school kid I believe) sent in the suggestion that it would save fuel by lightening the load.
I don’t think paint would have any effect on the foam insulation.
Hmm, that’s true. I was going off of a diagram I saw somewhere, Newsweek maybe. I’m probably misremembering. I also thought that the tank was contstructed something like a giant Thermos bottle, with a gap between the inner and outer skins to minimize heat transfer.
