NASA warned nine years ago over danger of lift-off routine

NASA was warned nine years ago that the space shuttle could fail catastrophically if debris hit the vulnerable underside of its wings during lift-off the very scenario that may have brought down Columbia.

After receiving the warning, NASA made changes in materials and flight rules to lessen the risk of debris breaking loose, Paul Fischbeck, an engineering professor at Carnegie Mellon University who conducted the 1994 analysis, said yesterday.

"There are very important tiles under there. If you lose the tiles on those stretches it can cause the shuttle to be lost," he said.