Heat Tile Damage Main Suspect in Cause of Disaster

CAPE CANAVERAL, Fla. Investigators trying to figure out what destroyed space shuttle Columbia focused immediately on the possibility that its thermal tiles were damaged far more seriously than NASA realized by a piece of debris during liftoff.

Just a little over a minute into Columbia's launch on Jan. 16, a chunk of insulating foam peeled away from the external fuel tank and smacked into the left wing, which like the rest of the shuttle is covered with tiles to protect the ship from the extreme heat of re-entry into the atmosphere.

On Saturday, that same wing started exhibiting sensor failures and other problems 23 minutes before Columbia was scheduled to touch down. With jus