Shuttle launch delayed
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KENNEDY SPACE CENTER, Florida (CNN) -- The first space shuttle launch since the 2003 Columbia disaster will not take place until late this week at the earliest, NASA spokesman Mike Rein said Friday.
NASA previously had said the shuttle Discovery could lift off as soon as Sunday, although it was unlikely.
The launch originally was scheduled for Wednesday, but it was scrubbed 2 1/2 hours before liftoff because of a faulty fuel sensor.
The space agency has until July 31 to attempt a launch or must wait until September.
"We are still looking at launching during this window," NASA spokesman Allard Beutel said.
Beutel said the delay will allow NASA "more time to work on our troubleshooting plan." (Full story)
As for Discovery's seven crew members, they remain at Kennedy Space Center in Florida but could return to their home base in Houston, Texas, because of the delay.
Controllers called off the highly anticipated launch earlier this week after the Discovery crew already had been strapped in for the mission.
During a prelaunch test, a problem appeared in one of four hydrogen-fuel gauges in Discovery's external fuel tank.
When the spacecraft's external tank had been loaded, fuel sensors appeared in the "wet" position, indicating that the tanks were full, said Steve Poulos, NASA's orbiter project manager.
To test the sensors, commands were sent that should have changed their readings to the "dry," or empty, position. But one of the sensors didn't change, indicating a problem, Poulos said.
At that point, controllers scrubbed the launch.
The sensor that malfunctioned is one of four that monitor hydrogen levels in the external fuel tank.
The redundancy is designed to keep the shuttle's engines from shutting down if more than one sensor fails in flight and mistakenly shows low fuel.
Wayne Hale, deputy shuttle program manager, said the mission can't go forward until the problem is fixed because launch protocols require all four sensors to be working.
A similar sensor problem cropped up during a test of the external fuel tanks in April, which engineers were never able to isolate.
Hale said NASA managers were comfortable with going ahead with the scheduled launch because the tank had been changed, along with all of the wiring and boxes in the sensor system, and all of the components were successfully tested.
'Minor repair' among mishaps
A series of mishaps marked the last 24 hours before Discovery's scheduled launch Wednesday.
On that morning, it appeared foul weather might postpone the high-profile mission. Repairing a ground heater earlier in the morning had delayed filling the massive external fuel tank.
On Tuesday, a cockpit window cover fell off and damaged two protective tiles near the orbiter's tail section.
But it was the fuel sensor that stopped the launch.
NASA has committed to daytime launches for the next two missions to ensure ideal lighting conditions for cameras to scrutinize the shuttle's ascent into orbit.
The mission would be the first shuttle flight since February 1, 2003, when Columbia disintegrated over Texas while returning from orbit, killing all seven astronauts on board.
The loss of the Columbia was blamed on damage to a heat-resistant panel. The panels and insulating tiles make up the shuttle's thermal protection system.
NASA concluded a piece of foam from Columbia's external fuel tank hit the shuttle's wing during liftoff, punching a hole in the reinforced carbon-carbon panel and allowing super-hot gas into the wing during re-entry.
NASA shut down the program and made safety improvements to the shuttle fleet recommended by a blue-ribbon panel that investigated the disaster.
For most of its scheduled mission, designated STS-114, the crew will devote time to inspecting and testing repairs. Discovery also plans to deliver much-needed supplies to the international space station.
CNN's Kate Tobin and Marsha Walton contributed to this report.
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