[agincourt1415]

You need to understand, at 12,000 miles per hour, if only one tile had been hit and damaged other tiles on reentry would have peeled off, the damage on the ascent wouldn't have set off any alarm bells, because the Shuttle has landed before with tiles missing, it was a chain of circumstances, unfortunate and now we learn that tiles are not a safe skin to have on the Shuttle.

They will probably have to reopen the National Aerospace Plane Program, and severly limit the number of astronauts on the the Shuttle.

[Jael]

It isn't that the tiles are not safe. It's the foam insulation on the fuel tank. And they have known about it since 1997.

"A review of the records of the STS-86 records revealed that a change to the type of foam was used on the external tank. This event is significant because the pattern of damage on this flight was similar to STS-87 but to a much lesser degree. The reason for the change in the type of foam is due to the desire of NASA to use "environmentally friendly" materials in the space program. Freon was used in the production of the previous foam. This method was eliminated in favor of foam that did not require freon for its production. MSFC is investigating the consideration that some characteristics of the new foam may not be known for the ascent environment."

http://216.239.33.100/search?q=cache:ryqlvTHKXEgC:ltp.arc.nasa.gov/space/team/journals/katnik/sts87-12-23.html+greg+katnik+tile+damage&hl=en&ie=UTF-8