![]() ![]() The defuser onDiscovery's tank is different from those on all past external tanks and willeventually be swapped out with an older version, she added. "We don't like flying right onthe edge."Ĭolemansaid one potential culprit is a defuser, a sort of mesh screen that that sitsat the very top of the hydrogen tank and disperses fuel in a manner thatprevents hot spots from developing on the tanks aluminum skin. "We've gotto understand it," Coleman said of the glitch. In a normallaunch, the valve cycles between eight and nine times. The valve apparently cycled the exactnumber of times - 13- as it did during the April 14 tanking test, which is justshy of breaching launch restrictions for an actual space shot. ![]() One concernnot solved in the May 20 test revolved around a pressurization valve at thevery top of Discovery's external tank. ![]() "It probably points tothe fact that.some kind of connection wasn't exactly right." "The mainengine cutoff sensors worked perfectly," Parsons said. The result, apparently, was a fully function sensorsuite during the second test fueling. Since then, padengineers have swapped out wiring and rechecked the connections running betweenDiscovery and its tank. Launchrestrictions require that all four sensors function properly before liftoff,though two of the devices cut out in the April 14 test. The sensors make sure Discovery's engine shutdown before its fuel tank runs completely dry, NASA officials said. Shuttlemanagers ordered Friday's test to reexamine a set of four sensors that monitorliquid hydrogen propellant levels inside Discovery's external tank to ensuremain engine cutoff during launch. "We've beenaware of this and we have a way to ensure we deploy the ," Parsons said."I don't believe this is going to be a real big problem, this is just anoperational workaround." Shuttleengineers will soon install the new heater to the expandable bellows portion ofa liquid oxygen feed line on Discovery's replacement fuel tank to prevent icebuildup.Īnotherconcern revolving adequate clearance between Discovery's new orbitalboom - which astronauts will use to scan the orbiter for damage - and avital communication antenna has been addressed, NASA officials said, addingthat the separation between the two devices is slim during deployment. If shuttle engineers push hard, however, they could accomplish thefeat by the window's opening, he added. NASA launchdirector Michael Lienbach said the addition of a third tanking test could pushDiscovery up to a week into its current launch window, which runs from July 13to July 31. "Right now,I don't have a third tanking test in my plan," Parsons said, conceding thatsome shuttle officials believe such a test could be warranted, but have agreedto look over the data from today's test first. NASA officials, however, could call for that extra test afterreviewing data from Friday's activity. The tank was original slated for NASA's follow-up mission toSTS-114, STS-121 aboard Atlantis.īut thereare no current plans to check that replacement tank as well by pumping it fullof the liquid oxygen and liquid hydrogen fuel Discovery consumes duringliftoff. Investigators later found thatlaunch debris, which struck Columbia's left wing during liftoff, caused theaccident.ĭespitetoday's test, Discovery will eventually fly with a completely differentexternal tank, one which already stands ready to accept the orbiter at themassive 52-story Vehicle Assembly Building (VAB) just over four miles away fromthe launch pad. 1, 2003, when the Columbiabroke apart during reentry, killing its crew. NASA'sspace shuttle fleet has been grounded since Feb. Theirspaceflight will also deliver vital consumables, science equipment and othercargo to the International Space Station, where the Discovery crew plans toperform no less than three space walks. Thehumidity today allowed more ice to form on Discovery's tank today than in theprevious test, but amounted to little more than frost, shuttle officials said.Ĭoncernsover the potential fatal danger posed by icedebris shaking off the tank prompted shuttle engineers to devise a newheater to limit the hazard.ĭiscoveryand the STS-114 crew are set to launch no earlier than July 13 on mission totest new hardware and procedures expected enhance space shuttle safety. ![]() "It was agood day," said Sandy Coleman, NASA's external tank project manager, during theteleconference. IfDiscovery's STS-114 crew - NASA's first shuttle astronauts to fly since the2003 Columbia disaster - had been aboard the orbiter, conditions would havebeen ripe to launch them into space. ![]()
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