NASA Postpones Shuttle Launch to at Least Late February

Repair work to space shuttle Discovery's external fuel tank begins in the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida. Technicians will modify 32 support beams, called stringers, on the tank's intertank region by fitting pieces of metal, called radius blocks, over the stringers' edges where they attach to the thrust panel area. Photo credit: NASA/Jack Pfaller

Jan. 7, 2011

NASA managers are evaluating potential launch dates for space shuttle Discovery in late February and working to see if International Space Station on orbit operations would allow a launch as early as Feb. 24. More will be known next week and managers hope to set a launch date by the end of next week.

Progress continues to be made in understanding the most probable cause of cracks discovered on Discovery’s external tank mid-section, known as the intertank, where small cracks developed during the Nov. 5, 2010, launch attempt. Four additional small cracks were found during thorough X-ray of the backside of the tank after Discovery was returned to the Vehicle Assembly Building before Christmas.

Plans are for the repair work to continue through the weekend. The shuttle program also reviewed the plan to modify as many as 32 additional stringers with radius blocks, which will provide added structural support in areas known to carry much of the structural load of the external tank. These radius blocks essentially fit over existing stringer edges through which the securing rivets are installed to provide additional structural support. The radius block modification is a known and practiced structural augmentation technique used extensively on the intertank. This work should begin as soon as the repairs to the three stringers with the four additional small cracks have been completed, likely in the next day or so, and the modification of the additional 32 stringers is expected to be complete next week.

NASA managers will meet with Space Shuttle Program officials Monday to review the progress to date and the forward plan. A determination of the need and viability for the installation of additional radius blocks on all remaining stringers will be made sometime next week. With the work remaining, the potential for additional modifications yet to be defined, and further reviews pending, the decision was made Thursday to allow the teams additional time and delayed the targeted launch date out of the early February launch window. Launch dates for Discovery and Endeavour will be discussed at next Thursday’s Space Shuttle Program Requirements Control Board meeting.