From: http://ltp.arc.nasa.gov/space/ask/landing/Black_tiles_falling_off.txt
"If more than a few were lost from the same area, though, the heat could get bad enough to cause damage to the aluminum skin. Nobody wants to see what would happen if the wings started to deform like taffy, so the tiles are each pull-tested before each flight to ensure the best possible adhesion. Repairing in orbit would be nearly out of the question. For one thing, adhesives don't work well in space (all the volatiles freeze or evaporate instantly), and for another, the tiles are different shape, so there's no way to carry a spare for everything. The astronauts prefer that everything be gotten right on the ground!" And an astronomer from california reported seeing stuff fall off while over his head. It looks like the landing gear area is the place it started. It will be interesting to see if they can figure out what actually happened, but it's clear that even if they knew there was a problem, there's nothing they could have done other than burn up. Bummer. Patience, persistence, truth, Dr. mike
