"Then they spent a week or two in cold soak on orbit." That downplays the viciousness of that environment, "The atmosphere in low Earth orbit is comprised of a

"Then they spent a week or two in cold soak on orbit." That downplays the viciousness of that environment, "The atmosphere in low Earth orbit is comprised of about 96% atomic oxygen." (http://www.nasa.gov/topics/technology/features/atomic_oxygen.html http://www.nasa.gov/topics/technology/features/atomic_oxygen...), it's truly corrosive stuff. I wouldn't be surprised to learn at least one component of the SSME was, or was initially, susceptible to it. A look at more hits from https://www.google.com/search?q=atomic+oxygen+space+shuttle https://www.google.com/search?q=atomic+oxygen+space+shuttle could be instructive.