Discovery is grounded until at least the end of the month by a hydrogen gas leak. The leak forced NASA to call off last Friday's launch attempt.
Later, a 20-inch crack in the foam insulation of the fuel tank was discovered.
On Wednesday, workers removed sections of the damaged foam for analysis. They were surprised to find two cracks in the actual aluminum surface of the tank.
NASA spokesman Allard Beutel says tank cracks like this have been fixed before at the production facility in New Orleans. But the work has never been attempted at the launch pad. Beutel says engineers are looking at what it would take to fix the tank at the pad.
Based on experience repairing similar cracks on other tanks, sources said, engineers believe the damage can be fixed at the pad before the next launch window opens at the end of the month, reports CBS News space consultant Bill Harwood.
NASA managers are expected to order a tanking test to make sure the new hardware is leak free before moving forward with another countdown, sources told Harwood. And that assumes the crack repair work goes well. To minimize the impact of a fueling test on other pad operations, only liquid hydrogen would be loaded into the external tank's lower section to confirm the replacement vent line attachment is working properly.
It is not yet clear what caused the underlying crack, Harwood reports. It presumably could have been triggered by temperature-induced stress as the tank was loaded with supercold liquid oxygen and hydrogen rocket fuel.
The year's final shuttle launch window opens Nov. 30 and closes Dec. 5 or 6, Harwod reports. If Discovery is not off the pad by then, the flight will slip to the end of February because of conflicts with other space station missions; a prohibition against flying over New Year's to avoid possible year-end rollover issues with the shuttle's software; and because of temperature constraints related to the space station's orbit.
Whether Discovery's launch team can complete the leak repair and fix the crack damage in time for a Nov. 30 liftoff is not yet known, but engineers are cautiously optimistic, Harwood reports. The schedule is considered "success oriented," however, and there is little margin for error.