Thanks! You might find Wayne Hale's (Space Shuttle Program Manager or Deputy for 5 years, a Space Shuttle Flight Director for 40 missions) 10-year retrospective on the Columbia crash interesting:
https://waynehale.wordpress.com/category/after-ten-years/
Also, I recall reading somewhere that the chairman of the Columbia Accident Investigation Board, Admiral Harold Gehman, decided to conduct a test to see if the piece of foam seen hitting the leading edge could have broken it. As, at the time, it had not been decided to end the shuttle program, this was not an easy decision, as it meant sacrificing an essentially irreplaceable spare part. What finally convinced Gehman to go ahead was the fact that a great many NASA engineers firmly believed it could not possibly have been the cause.
