SM wrote:

"It may have hit the wing, blew a hole through it, and kept right on going fully intact."
and
"This photo from NASA's Hypervelocity Impact Technology Facility clearly shows that impacts that perforate a flat panel may result in a larger cloud of debris"

With all due respect and with the caveat that I am not a trained Physicist, I think it should be pointed out that the 'chunk' was going *maybe* mach 2 WRT the wing, which is not really the hypersonic velocity you compare it to and not even in the same order as a good high-power rifle bullet, If memory serves me. No contest that if it was a substantial material it would have blown a hole right through the orbiter, but at that lower speed, it would have been more the 'gaping' hole. Like the cannons I used to build in my childhood- the long barrel pellet-shooter would leave a neat hole in the steel bucket, while the short Lead Ball cannon would split it in half! ;-)
(This all assumes that the chunk was substantial and very hard, like the SRB material you speak of)

Also, while it is true that the object *looked* white, I'm not sure we can trust that. I bet it is probably not the case that the foam of the tank is rust-red all the way through, so suppose that this chunk looks white because we are seeing a non-colored side of the broken-off chunk?

Also, at that distance, The default color in the images seems to be white. Other things might confound, maybe it is coated with a thin dusting of frost? Maybe the color comes from condensation as it passes through the atmosplere?

Also, those SRB's don't have much wiggle room in terms of strenght of the walls of the tube and the pressure they contain. If a big chunk of the wall of an SRB was blasted off/dislodged, I think a challenger style catastrophe would have followed. Also, to employ the cannon analogy again, I think it would have shredded right through the wing, visably, if it had been as substantial as a structural chunk of SRB skin.

Davin L.