Technicians install radius block modifications to the stringers on shuttle Discovery's external fuel tank. Photo Credt/NASA photo
Shuttle Discovery’s final mission will miss the next launch opportunity, giving experts more time to troubleshoot small cracks in the stringer section of the spacecraft’s external fuel tank.
NASA managers made the decision Thursday not to attempt a launching of Discovery’s final flight during a window that extends from Feb. 3 to Feb. 10.
Shuttle managers are not expected to address the launch date question until Jan. 13. The mission has been stalled since Nov. 5, when an unrelated hydrogen leak forced a launch scrub.
The next launch window opens Feb. 27 and extends through March 6.
Since the scrub, technicians have discovered eight cracks on the tips of five external tank stringers. In all, 108 support beams encircle the 154-foot-long fuel tank to separate internal oxygen and hydrogen containers. Engineers believe the cracks may have formed at the tops of the 21 foot long aluminum lithium beams during the November launch attempt in response to falling temperatures that accompanied the flow of chilled oxygen and hydrogen propellants.
An investigation into the cause of the damage is under way by personnel from several NASA installations.
Earlier this week, managers ordered a “radius block” modification to nearly three dozen stringers to prevent additional cracking. On Thursday, they deferred a decision on whether to extend the modification to all 108 beams.
The beefed up support beams are distributed on either side of two fuel tank thrust panels. The panels face the Discovery’s solid rocket boosters and shoulder most of the load as the shuttle lifts off.
Discovery’s six astronauts have trained to equip the space station with an equipment storage compartment and an external platform to hold spare parts.
