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15 Nov USA: NASA Digging Out from Shuttle Woes
By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) – NASA's quest to resume space shuttle flights has slowed to a crawl at the Kennedy Space Center, where technicians were meticulously testing the fragile cloth strips that forced an unprecedented and risky spacewalk during the last shuttle mission.
The tests on the cloth strips were in addition to extensive changes to the insulation on the shuttle's external fuel tank and other changes designed to make the spacecraft safer. NASA hopes to launch the spaceship in May for its second mission since the 2003 Columbia accident.
Workers have removed more than 2,300 strips, known as gap fillers, from between the ceramic tiles that form shuttle Discovery's heat shield.
About 65 percent cannot be tested and are immediately removed. For the remaining 35 percent, NASA technicians test how well the cloth strips are bonded to the ship by tugging on them for three seconds with five pounds (2.25 kg) of force. About half fail the test and are removed.
A protruding gap filler, which is about the width of a business card, could interfere with air flow around the shuttle during its supersonic descent through the atmosphere for landing and cause the ship to overheat.
"We've got to fly again and we've got to get this done in order to fly," said Pat Floyd, who heads the project United Space Alliance, NASA's prime shuttle processing contractor.
New gap fillers that have been carefully measured and cut to fill each space will have to be installed before the ships are ready to fly, a process that will take months.
During the agency's first post-Columbia mission in July, two gap fillers came loose, prompting flight directors to order a risky repair by spacewalking astronauts Steve Robinson and Soichi Noguchi.
INSULATING FOAM, HEAT SHIELD REPAIRS ALSO UNDERWAY
NASA has twice grounded the fleet because of problems with the tank's insulating foam that led to Columbia's destruction and the deaths of seven astronauts.
The ongoing repairs to the shuttle have heartened NASA officials hoping for a spring launch.
"I'm beginning to feel very bullish about the possibility of making May," shuttle program manager Wayne Hale said.
It took three months just to inspect the 12,000 heat-shield tiles on the front portion of Discovery, which get the most heat during the shuttle's re-entry into Earth's atmosphere.
NASA grounded the shuttle fleet following the 2003 Columbia disaster to fix problems with the ships' fuel tanks. A piece of foam insulation flew off Columbia's tank during launch and smashed into the ship's wing.
The damage triggered the breakup of the shuttle as it flew over Texas 16 days later en route to its landing strip in Florida. The problem reappeared during the July launch of Discovery, prompting NASA to ground the fleet again for additional tank repairs.
The space agency is changing its methods for applying some of the insulating foam on the fuel tanks and modifying the design of new heaters that were installed on the tanks after the Columbia accident.
Engineers believe tiny streams of air blasted through the foam where the heater wires were located. When the air came into contact with the cold skin of the tank it caused the overlaying foam to pop off.
Source: Reuters
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