Engineers say they are unsure if the cracks are related to the problem of foam breaking off the tank during shuttle launches.
"How do these cracks that we've found figure into that? We don't know," John Chapman, manager of the External Tank Project at NASA's Marshall Space Flight Center in Huntsville, Ala., said at a press conference Tuesday. "It would certainly be premature to say the cracks play a factor in that. We don't know that right now. But they might."
Shuttle program manager Wayne Hale Jr. said the agency is "trying to come to grips with what that means."
Investigators concluded that foam breaking off the Space Shuttle Columbia's external fuel tank and striking the orbiter left damage that caused Columbia to disintegrate as it tried to re-enter the Earth's atmosphere on Feb. 1, 2003, killing all seven astronauts on board.
After the Columbia disaster, NASA officials pledged to solve the foam problem but were stunned when a one pound piece of foam broke off during Discovery's much hailed return to flight on July 26. The piece of foam did not strike the orbiter and Discovery safely completed its 14-day mission.
Since the Discovery foam incident, NASA grounded all shuttle flights. The agency hopes to fly the next shuttle in May, providing the foam problem is solved.
"We're going to get to the practical solution to ensure that we don't lose large amounts of foam off that tank," Hale said Tuesday. "That's clearly something that we've got to do to fly safely."
NASA officials said the tank with the newly discovered cracks had been filled with liquid hydrogen fuel during launch pad testing in the spring, and had subsequently been shipped back to the Michoud, La. plant.
Chapman said expansion of the tank as it was filled and emptied of fuel may have contributed to the cracking, the Houston Chronicle reported.
The foam is applied to the external tank to prevent ice from forming that might damage the shuttle during launch.
-- Compiled from wire reports and other media sources
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November 23, 2005, 1pm EST
