My friend and geek and rocket scientist, Cap'n Nemo of NOLA put this together for me as I was questioning what I saw on the live broadcast. I find it fascinating and asked if I could share it. First bit is full speed, second bit is slow speed.
"The thing is, it didn't blow off; it popped off. If it had blown off, it would have started toward the aft end of the shuttle right away. Had to be cryopumping or something that popped it up. Cryopumping can be caused by a void in the foam. Air in the void gets liquefied from the cool temperatures around the Intertank (which is the ribbed section between LH2 (aft) and LO2 (forward) tanks. That creates a vacuum and more air can seep in. But the void heats back up as the tank empties its cold contents. The air in the void gasifies and pop goes the foam!"
