Discovery launch set to go
Damaged tiles fixed on craft's tail section after mishap
By Thom Patterson
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KENNEDY SPACE CENTER, Florida (CNN) -- The launch of the space shuttle Discovery will go ahead as scheduled Wednesday after technicians replaced two protective tiles damaged near the spacecraft's tail Tuesday, a NASA spokeswoman said.
The tiles were damaged when a cover panel on the No. 7 cockpit window fell off as the orbiter sat on the launch pad late in the afternoon, officials said.
"Everything looks good," Discovery vehicle manager Stephanie Stilson told reporters. "This is a minor repair for us."
Wednesday's scheduled launch will be the first mission for the shuttle program since the Columbia disaster in February 2003 that killed all seven astronauts aboard.
Liftoff is set for 3:51 p.m. ET from launch pad 39B. Discovery has been outfitted with an expansive array of safety modifications to avert another disaster.
The plastic-and-foam window cover struck the left-hand housing for the shuttle's orbital maneuvering system -- the network of small rocket engines that control Discovery as it orbits -- Stilson said.
The loss of the Columbia was blamed on damage to a heat-resistant panel. The panels and the 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, allowing super-hot gas into the wing during re-entry.
Stilson said the window cover -- which weighs less than 2 pounds -- was discovered after it had fallen about 65 feet.
The cover is designed to protect the windows while the shuttle is on the launch pad and is removed before liftoff. NASA did not know how the shield had come loose, she said.
The piece of foam believed to have doomed Columbia also weighed less than 2 pounds.
Engineers at NASA's mission control in Houston, Texas, would "run all the numbers" overnight to ensure the orbiter is fit for launch, Stilson said.
"We're very confident that there will be no concern tomorrow morning," she said.
Discovery was cleared to "go" earlier Tuesday, despite a 40 percent chance of bad weather at launch time.
"Can there be something that we don't know about that can bite us? Yeah. This is a very tough business," NASA Administrator Michael Griffin told reporters at a space center news conference. "But everything we know about has been covered."
NASA has committed to daytime launches for the next two shuttle missions to ensure ideal lighting conditions for the cameras that will scrutinize the shuttle's ascent into orbit.
In the two and a half 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 have also designed an orbital boom sensor system, which is a second robotic arm that is tipped with cameras and other instruments and mounted in the shuttle's payload bay.
Once in orbit, astronauts will use the boom to inspect the panels on the orbiter's wings and nose cone for any damage that might have occurred during launch.
But repairing damage to the protection system -- should any be found -- could prove difficult.
Engineers have been developing and testing plugs and crack-repair procedures for the reinforced carbon-carbon panels, as well as tile-repair techniques, for use in the event of damage.
Two such methods will undergo limited testing in orbit by Discovery astronauts, but mission managers acknowledge that their techniques will likely 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 two and half 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," Griffin said.
Discovery will also deliver much-needed supplies to the international space station.
Two and half years have passed since a shuttle, with its school bus-sized 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 13-day mission, designated STS-114, the crew will devote its time to inspecting and testing repairs.
CNN's Miles O'Brien, Marsha Walton and Kate Tobin contributed to this report.
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