SPACE CENTER, Houston - NASA investigators looking into what caused large pieces of foam to break free from the Columbia and Discovery have found nine small cracks in the foam of an external fuel tank.
But program administrators are not sure whether the cracks played any role in the foam separation from the space shuttles.
"Certainly, the cracks we found ... are interesting," said John Chapman, who is responsible for the production of NASA's external tanks. "We're still in the process of understanding what that means."
The shuttle fleet remains grounded while NASA figures out how to stop big pieces of foam insulation from breaking off the fuel tanks during liftoffs, a problem that led to Columbia's destruction in 2003 and reappeared during Discovery's July launch.
Wayne Hale, deputy shuttle program manager, said the agency is still working toward launching another shuttle next May, but won't let an arbitrary schedule dictate when the agency flies again.
Also, shuttle manager Steve Poulos said an investigation into what caused a thermal blanket to rip from near Discovery's cockpit during its summer mission determined faulty stitching led to the mishap.
NASA wasn't sure if it would be safe to return Discovery to Earth with the ripped thermal blanket and considered an unscheduled spacewalk to repair it. But after testing on the ground, the agency determined the blanket shouldn't cause a problem during re-entry and the shuttle landed safely Aug. 9.
Poulos said the agency has since inspected 486 thermal blankets on Discovery and Atlantis and plans to replace 100 of them.