CAPE CANAVERAL, Fla. -- NASA successfully conducted a tanking test of space shuttle Endeavour's external fuel tank today, to ensure repairs to tank's liquid hydrogen vent line were successful. All indications are that the vent valve and valve performed as expected, which paves the way for the shuttle to liftoff on a space station assembly mission on July 11.
FREE VIDEO: FREE VIDEO: ALL-ACCESS SUBSCRIBERS: ALL-ACCESS SUBSCRIBERS: ALL-ACCESS SUBSCRIBERS: At a press conference following the test, shuttle program Launch Integration Manager Mike Moses and STS-127 Launch Director Pete Nickolenko expressed confidence that the pesky leak, the source of two previous launch scrubs for Endeavour, had been fixed and that the shuttle is good to fly next week. "We're in really good shape," said Mike Moses after the test. "In this case, there were absolutely no leak indications and when we did transition all the way through the replenish operations, there were absolutely no leak indications whatsoever noted," added Nickolenko. During the test, the external tank was filled with liquid hydrogen and liquid oxygen, just as it is before launch. A hydrogen gas leak at the Ground Umbilical Carrier Plate, or GUCP, postponed Endeavour's launch attempts June 13 and 17. The GUCP is attached to the venting system and a 7-inch line is used to carry excess hydrogen safely away from the launch pad. As the tank is filled with the supercold liquid, some of it warms up and "boils off". To keep the pressure in the tank from increasing to much because of the extra gas, the excess is captured in the vent line where it is then routed to a "flare stack" at the launch pad perimeter and harmlessly burned off. Engineers determined the most likely cause of the leak is a slight misalignment in the External Tank Carrier Assembly. The assembly was fastened to the tank during manufacturing. The misalignment likely is putting uneven pressure on a Teflon seal, causing a small leak when extremely low temperatures occur during fueling. Technicians replaced the old seal with a two-piece seal that has a tighter, more flexible fitting and added small washers to counter any movement of the external tank carrier assembly as the tank is fueled. During the operation today, sensors barely detected the presence of any hydrogen gas at all. The peak measurement was a concentration of only 12 parts per mission, compared with 60,000 parts per million that was measured during the last two launch attempts. NASA has a limit of 40,000 parts per million (4 percent) in the vicinity of the shuttle stack. Higher concentration raise the risk of a potentially catastrophic hydrogen fire and explosion at the pad when the shuttle lifts off. Endeavour's launch on the STS-127 mission is targeted for 7:39:33 p.m. on Saturday, July 11. The 16-day mission to the International Space Station will feature five spacewalks and complete construction of the Japan Aerospace Exploration Agency's Kibo laboratory. Astronauts will attach a platform to the outside of the Japanese module that will allow experiments to be exposed to space. Endeavour will be commanded by Mark Polansky, flying with pilot Douglas Hurley, Canadian flight engineer Julie Payette, David Wolf, Christopher Cassidy, Thomas Marshburn and space station flight engineer Timothy Kopra. The shuttle will have just four days to get off the ground before standing down until July 27 in order to make room for a Russian Progress resupply ship, scheduled to launch on July 24. Endeavour must undock by the 27th so that the supply craft can dock with the station by July 29. If all goes according to plan, Endeavour will land back at Kennedy Space Center at 12:15 p.m. on July 27. (The Spacearium / Space Media Corporation)
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