Technicians at NASA Kennedy Space Center's Launch Pad 39A in Florida are moving ahead with plans for a tanking test for space shuttle Discovery's external fuel tank, which now will be no earlier than Friday, Dec. 17, weather permitting. Cold and windy conditions have slowed test preparation. The test will help verify repairs associated with cracks on the tops of two 21-foot-long, U-shaped aluminum brackets, called stringers, and help engineers determine what caused the cracks in the first place during Discovery's launch countdown on Nov. 5.
Shuttle managers also decided late Monday afternoon that following the tanking test they plan to roll Discovery back into Kennedy's Vehicle Assembly Building (VAB) to allow its external tank to undergo additional image scans. Rollback is expected to occur 4-5 days after the tanking test. Once in the VAB, technicians would collect X-ray data on stringers on the back side of the external tank midsection, called the intertank, which is not accessible at the launch pad. Additionally, the test instrumentation and foam insulation on those areas of the intertank would be removed and the area would be prepared again for launch. In parallel, the back side stringer inspections would take.
At the launch pad, crews currently are replacing foam insulation after installing 89 strain gauges and temperature sensors for the tanking test to precisely record movement and temperatures from the intertank as it chills and warms again during the loading of propellants and emptying process. The tank holds super-cold liquid oxygen and liquid hydrogen, which cause the tank to shrink by about half an inch.
Managers and engineers will review the data gathered from the tanking test and additional image scans before determining the next course of action. Currently, managers plan to have Discovery returned to the launch pad in January ahead of its next launch opportunity, which is no earlier than Feb. 3 at 1:34 a.m. EST.