This story was updated at 10:20 p.m. EST.
NASA has delayed the planned Feb. 12 launch of the space shuttle Discovery by at least a week to allow extra time to evaluate vital fuel valves on the spacecraft, agency officials said late Tuesday.
Discovery was slated to launch toward the International Space Station on Feb. 12 to deliver the last set of U.S.-built solar arrays to the orbiting laboratory. The mission is now scheduled to blast off no earlier than Feb. 19 at about 4:41 a.m. EST (0941 GMT), but an official launch target will be determined at a later date.
?By looking at it right now, we think it?s about a week delay, but we?re not going to put pressure on the team,? said John Shannon, NASA?s space shuttle program manager, in a briefing at the agency?s Kennedy Space Center in Florida. ?We?ll just let the information drive us.?
The delay is necessary to allow engineers time to be sure that pieces of Discovery?s flow control valves won?t chip off and damage vital plumbing between the spacecraft?s main engines and its 15-story external tank. The valves are used to keep the space shuttle?s hydrogen propellant tank pressurized as the orbiter rockets spaceward.
The valves were replaced on Discovery after engineers discovered damage to a similar valve that flew aboard its sister ship Endeavour last November.
During Endeavour?s Nov. 14 launch, a piece of one of three flow control valves chipped off, apparently from high-cycle fatigue, Shannon said. The valve functions much like a pop-up lawn sprinkler to funnel hydrogen gas from a shuttle's main engine back into its external tank to maintain proper pressure levels, he added.
Shannon said the damaged valve on Endeavour caused no serious harm during that shuttle?s November launch and NASA officials want to be sure the same will be true for Discovery when it flies.
?We don?t expect there to be a problem, but we don?t have the proof in hand,? Shannon said. ?We want to have that proof in hand before we commit to go fly.?
Shuttle officials announced Discovery's flight delay late Tuesday after a day-long meeting to discuss the orbiter's launch readiness.
NASA engineers plan to perform a series of tests to evaluate what effects valve debris could cause during ascent. Top shuttle officials are expected to discuss the results from those tests next week before setting an official new launch target.
Michael Leinbach, NASA?s launch director, said his team of shuttle workers is currently in a holding pattern until a new launch date is set.
?Once we?re given a launch date, we?ll get back into our processing,? Leinbach said.
Commanded by veteran spaceflyer Lee Archambault, Discovery?s STS-119 mission will launch seven astronauts toward the space station to deliver the outpost?s last set of U.S. solar arrays. Four spacewalks are scheduled during the two-week spaceflight. The mission will also ferry Japanese astronaut Koichi Wakata to the space station, where he will replace NASA spaceflyer Sandra Magnus as a member of the outpost?s three-person crew.
Space station mission managers, meanwhile, are tackling several issues to prepare the outpost for Discovery?s arrival this month and the planned shift to a larger, six-person crew later this year. They range from a recent vibration event associated with a Jan. 14 thruster firing to ongoing, but not insurmountable, glitches with new life support equipment.
NASA space station program manager Mike Suffredini said he is confident the glitches will be resolved and the station ready to support the first six-person crew in late May as planned.
Suffridini said that while the vibrations on Jan. 14, which occurred during a routine Russian thruster firing to boost the space station?s orbit, were stronger than the acceptable limits, they did not cause any structural damage to the outpost. During the two-minute, 22-second engine burn, the space station?s current skipper Michael Fincke of NASA reported that the outpost shook more than he?d ever seen in his two increments aboard, but he did not hear creaks or groans from the structure, he added.
A video from a camera inside the station showed items shaking back and forth.
?You can see things were moving around pretty good,? Suffredini said.
But despite the shaking, the event did not impact the space station?s 15-year design lifetime, he added.
Earlier today, space station managers in Russia and at NASA?s Mission Control in Houston canceled another planned thruster firing planned Wednesday. The next maneuver may take place sometime in March, Suffredini said.
Discovery?s STS-119 mission is NASA?s first of up to six planned shuttle flights for 2009. They include one final flight to overhaul the Hubble Space Telescope and a series of space station construction missions.
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