This story was updated at 1:40 p.m.EDT.
NASA'sfirst space shuttle to fly since the Columbia disaster will not liftoff untilJuly, a drastic delay that will force mission managers to miss the first of twolaunch windows this summer.
Spaceshuttle officials are now targeting a launch window opening July 13 for the space shuttleDiscovery, after it became clear that lifting off during the current window -which runs from May 22 to June 3 - would be unattainable. The new launch windowcloses July 31.
"We'regoing to return to flight, we're not going to rush to flight," said NASA chiefMichael Griffin in a press conference at the space agency's Washington, D.C.headquarters. "We're going to do it right."
Unresolveddebris issues, malfunctioning external tank sensors and soiled thermalprotection blankets contributed to Discovery's launch delay, which will push back preparations to deliver a large cargo pod tothe International Space Station (ISS). The delay will also allow more time to developplans to service the Hubble Space Telescope, Griffin said.
The spaceshuttle is sitting atop launch pad 39B at NASA's Kennedy Space Center (KSC) inFlorida as part of the agency's first return to flight mission STS-114. Acountdown test with the crew and orbiter stack is scheduled for next week atKSC.
The STS-114flight is slated to test a host of new tools and techniques designed toincrease shuttle flight safety, a direct response to the loss of the Columbiaorbiter and its seven-astronaut crew. Columbia broke up during reentry on Feb.1, 2003, which investigators later determined was a result of wing damagecaused by external tank debris shed two weeks earlier at the mission's launch.
"Every timewe've established a launch date, it's been on the best data available," saidWilliam Readdy, NASA's spaceflight program chief, during the press conference."Since we first established a launch date in June 2003, we've adjusted it ahalf a dozen times based on new data."
Ice debris and sensor glitches
It was newdata on the potential danger of ice debris striking the shuttle that pushed shuttlemanagers to set the new launch date. The ice, which tests have shown can break off in chunks of up to five inches long, forms on regions of a 17-inch wideliquid oxygen feed line running down the external tank.
Tankengineers had previously installed a drip lip to the area of most concern - a bellowsunit that expands and contracts - which reduced the risk of ice by about 70percent, NASA officials said.
"A verysmall piece of ice can cause problems," said NASA shuttle program managerWilliam Parsons said in a separate briefing today from Johnson Space Center(JSC) in Houston. "Ice does not cause the same damage foam...we understand foammuch better because we've done a lot of testing."
The damageto Columbia's wing leading edge was caused by a briefcase-sized chunk of insulationthat separated from the external tank during liftoff. Tank engineers have sinceredesigned portions of the tank to reduce the amount of foam shedding.
"Thetesting on the ice lagged behind the testing on foam, but was clearly put inplace," said Wayne Hale, deputy shuttle program manager at JSC, during thebriefing. "But we had plans on how to deal with it [and will] now that we knowthat we have to do something about it."
Shuttleengineers could install a removable heater to the bellows area to prevent icebuild-up. The heating unit is already expected to ride on the third externaltank to fly, and will likely be installed on another tank already inside NASA's52-story Vehicle Assembly Building to iron out assembly processes before a unitis attached to Discovery's fuel tank.
But Halesaid that heater assembly kits won't arrive at KSC until May 5, and there stillremains some testing to determine if they will ultimately fly aboard Discovery.
Earlierthis month, shuttle mission managers and launch workers performed a criticaltest of Discovery's revamped external tank, fueling it with 500,000 gallons ofliquid oxygen and hydrogen which the orbiter burns to reach space.
During thattest, problems were detected in two of the tank's four fuel sensors, used tomeasure liquid hydrogen propellant levels, for reasons engineers still do notfully understand. Four functioning fuel sensors are required in order to launchthe shuttle, Readdy said.
"I assureyou that four [sensors] of four is the launch commit criteria of STS-114 andSTS-121," Readdy added.
Thefollow-up to Discovery's test flight, the STS-121 mission aboard Atlantis will alsotest a series of new procedures and technologies for enhanced shuttle safety.
Other concernsalso included the accidental contamination of Discovery's thermal protectionblankets with hydraulic fluid, though Parsons said those concerns have beenlessened and the blankets could be cleaned, or even left alone, after further study.
ISS support and Hubble
Discovery'stwo-month launch delay will also affect space station operations, whereExpedition 11 astronauts Sergei Krikalev and John Phillips were anticipatingthe shuttle's May arrival to bring a wealth of food, supplies and new scienceequipment.
NASA'sspace shuttle fleet has been grounded since the Columbia accidents, leavingspace station crews dependent on Russian Soyuz spacecraft to reach the ISS andthe automated Progress vehicles for cargo deliveries. Discovery will deliver alarge cargo container to the ISS, as well as large station components thatcurrently cannot be launched aboard any other spacecraft.
WilliamGerstenmaier, NASA's ISS program manager, said more water - currently the keyconsumable aboard the station - would be added to a Progress vehicle set tolaunch in June.
"Each oneof our international partners was disappointed that we're not going to launchthe shuttle in that first window, but I think they understood clearly why we'redoing it," Gerstenmaier said.
During the earlier briefing today, Griffin told reporters thathe had already informed key members of Congress Thursday evening that he woulddirect engineers at Goddard Spaceflight center to start preparing for a spaceshuttle servicing mission to Hubble on the assumption that one ultimately willgo forward.
Griffin said a final decision is still pending NASA'ssuccessful return to flight with the launch of the shuttle Discovery. However,with that launch now delayed nearly two more months, Griffin said the Goddardteam has to get started now to preserve the option of saving Hubble before thepopular telescope is scheduled to go dark around 2008.
"[But] We're not going to allow Hubble preparations tointerfere with return to flight," Griffin said.
Space News Staff Writer Brian Bergercontributed to this report.
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