What happened while Discovery was ascending?

NASA officials are investigating whether a new material used to build part of space shuttle Discovery’s fuel tank played a role in allowing a large piece of debris to fly off the tank during ascent. President Bush called as the space shuttle crew prepared for a high-stakes task: an unrehearsed maneuver in which a spacewalker will go beneath the craft on Wednesday to repair the filler sticking out from the ship’s thermal tile belly. NASA says the protruding material could cause dangerous overheating during re-entry and lead to another Columbia-type disaster.