Shuttle launch delayed until at least Saturday
Faulty fuel sensor forces NASA to scrub Discovery's liftoff
By Thom Patterson
Mission specialist Soichi Noguchi leaves the orbiter after Wednesday's launch was scrubbed.
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KENNEDY SPACE CENTER, Florida (CNN) -- A faulty fuel sensor aboard the space shuttle Discovery on Wednesday forced NASA to delay its launch until at least Saturday.
Wednesday's attempt to launch, on the first day of a launch window that closes July 31, would have been the space shuttle program's first mission since the Columbia disaster 2 1/2 years ago.
"We would not in any conceivable way be ready to launch before Saturday," Wayne Hale, deputy shuttle manager, told reporters Wednesday afternoon.
Saturday's launch would be at 2:40 p.m. ET.
"We're going to go where the technical data leads us until we solve this problem."
NASA said the sensor device was showing low fuel levels despite the exterior tank having been filled just hours before.
"It will take some time really to understand what to do to remedy the situation," said NASA spokesman George Diller.
"There are long faces here in the control center and around the site. Everybody was so looking forward to flying today," Diller said.
Crew members were already aboard the orbiter when the launch was canceled.
A series of mishaps marked the last 24 hours before Discovery's scheduled launch.
On Wednesday 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, a little more than three hours before the scheduled 3:51 p.m. ET launch.
The sensor monitors the amount of super-cold hydrogen fuel in the tank and tells the orbiter's engines to shut down if there's not enough fuel.
A launch controller described it as "a low-level fuel sensor in the external fuel tank, one of a set of four -- two of which are needed to work."
About 10 miles from the launch site along the Banana River, scores of shuttle watchers -- many wearing shorts and swim wear -- had gathered hoping for a liftoff when word reached them about the scrub.
"I'm disappointed and I'm leaving tomorrow, so I will miss it," said Rick Nakazawa, 47, of Santa Barbara, California. "It was exciting, you know, I'm glad I came out. I sure don't regret it, but it kind of sucks, pretty much."
Many in the crowd sought shelter under umbrellas or had constructed makeshift tents from bed sheets.
Lacey Nielsen, of Alta, Iowa, expressed a bit of optimism about it all.
"I am really bummed, but at least for their safety they caught it before anything bad could happen," Nielsen said. "Hopefully it's nothing big and they will be able to get done and put up into outer space."
'Minor repair' among mishaps
In Tuesday's incident, a plastic and foam cover fell about 65 feet from a cockpit window and damaged two protective tiles near the orbiter's tail section. The tiles were replaced.
Discovery vehicle manager Stephanie Stilson described it as "a minor repair for us."
The cover, which weighs less 2 pounds, is designed to protect the shuttle's windows while it is on the launch pad and is removed before liftoff. NASA did not know how the shield had come loose, she said.
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 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.
Shuttle program gets overhaul
In the 2 1/2 years since the Columbia accident, NASA has undergone a wrenching overhaul of the shuttle program.
The shuttle has a new fuel tank designed to prevent foam chunks of the size that downed Columbia from breaking off and hitting the spacecraft.
NASA engineers also have designed an orbital boom sensor system, which is a second robotic arm tipped with cameras and other instruments and mounted in the shuttle's payload bay.
Once in orbit, astronauts will use the boom to inspect panels on the orbiter's wings and nose cone for any damage that might occur during launch.
But repairing damage to the protection system -- should any be found -- could prove difficult.
Engineers have been testing plugs and crack-repair procedures for the reinforced panels as well as tile-repair techniques in the event of damage.
Two such methods will undergo limited testing in orbit by Discovery astronauts, but mission managers acknowledge that the techniques likely will need to be modified before they can be certified.
Most NASA engineers agree that astronauts would never be able to repair a hole the size of the one that doomed Columbia.
"The past 2 1/2 years have resulted in significant improvements that have greatly reduced the risk of flying the shuttle. But we should never lose sight of the fact that space flight is risky," said NASA Administrator Michael Griffin.
Discovery plans to deliver much-needed supplies to the international space station.
More than two years have passed since a shuttle, with its school bus-size payload bay, visited the station.
Discovery will deliver a replacement gyroscope, an external storage platform and an Italian cargo carrier called Raffaello.
The storage platform is needed for upcoming flights when it will be used to assemble the rest of the station.
For most of its scheduled mission, designated STS-114, the crew will devote time to inspecting and testing repairs.
CNN's Miles O'Brien, Geneen Pipher, Kate Tobin, Marsha Walton and KC Wildmoon contributed to this report.
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