Shuttle Evaluated After Foam Debris Shower
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Frank Morring, Jr.
Space shuttle experts are evaluating the heat shield protecting Endeavour following what appeared to be the worst release of insulating foam from its external tank since the Columbia accident.
Experts at Johnson Space Center should have plenty of data to evaluate, including the results of a detailed laser survey with the orbiter's robotic arm on July 16 that covered the reinforced carbon-carbon (RCC) panels on the nose cap and wing leading edges. Also on tap is digital telephotography by the International Space Station (ISS) crew during the back-flip rendezvous pitch maneuver upon rendezvous on July 17.
Early results were encouraging, managers say. A set of at least four marks on the black tile in the starboard chine area appears to be less serious than a similar ding observed during the STS-125 mission in May, when no action was required. Other debris seen falling from the intertank stringer probably came so late in the ascent that there wasn't enough atmosphere to slam it into a delicate RCC panel, as happened with Columbia.
Managers also want to know why so much foam fell from the external tank, after all the work that went into preventing it after the accident. One early suspect is the repeating fill-and-drain cycles Endeavour's tank experienced in the month-long runup to launch. The tank was filled with cryogenic propellants six times and drained five times before the July 15 liftoff, as a persistent gaseous hydrogen leak and coastal-Florida thunderstorms forced five scrubs.
Endeavour's seven-member crew is set to spend 16 days in space delivering the final element of Japan's Kibo module -- an experiment platform exposed to open space -- and outfitting it with experiments. In the course of five spacewalks they also are scheduled to replace the oldest set of batteries on the station, deliver spare parts that will be too large to fly on any of the vehicles that can dock with the station after the shuttle retires next year, and replace Japanese ISS crewmember Koichi Wakata with NASA's Tim Kopra.
Photo credit: NASA
