I’ve been having a hard time understanding the foam hypothesis for the damage that caused the Columbia disaster, but in an independent experiment a 1.67-lb. chunk of foam shot from a gas cannon at around 530 mph at a fullscale mockup of a shuttle wing produced a worrisome gap when it struck a glancing blow on the very first attempt. The mockup, of fiberglass, is if anything more resiliant than the esoteric carbon fiber of the real thing. Like me, investigators were apparently skeptical before the experiment:

“Investigators have already concluded that a hole in the shuttle’s left wing let in the superheated gases that destroyed the wing, and they knew that a piece of foam struck the wing on launching. But they would not have been able to link the two convincingly without experimental evidence, and some of them had been worried that the experiments might not produce any wing damage.” NY Times

Another report says that the foam may have done its damage by dislodging a ‘T’ seal between two segments of the wing, opening up a gap along a seam. Analysis of a recorded radar echo of a piece of debris that flew off from the wing after the chunk of foam hit it suggests it is consistent with a ‘T’ shape.