NASA said Thursday that engineers are testing the foam insulation bonding on the space shuttle Discovery's external fuel tanks before it heads to the International Space Station on August 25.
NASA has been cautious about shuttle exit and return conditions since the shuttle Columbia blew apart in 2003 as it returned from a 16-day space mission.
A chunk of insulation that broke off from Columbia's external fuel tank during takeoff gouged the craft's left wing heat shield, allowing superheated gases to melt the shuttle's internal structure.
The space shuttle then exploded, killing all seven astronauts onboard.
Pieces of insulating foam have peeled off during blastoff on previous shuttle Endeavor and Atlantis missions, said shuttle program manager John Shannon.
"Other than that, the vehicle is in great shape and we are ready to proceed for the new flight readiness review next Tuesday," Shannon told reporters.
Seven astronauts will travel aboard Discovery, including Nicole Stott, who will remain on the ISS for three months replacing Tim Kopra, who has been on the orbiting station since July.
Discovery will be transporting several tonnes of food and supplies as well a freezer to store test results. "It's a big flight to fully utilize the ISS," said space station deputy program manager Kirk Shireman.
Also bound for the ISS: the COLBERT, a second exercise treadmill for the mission, named after popular US television comedian Stephen Colbert.
"With six people on board it's hard to schedule running time on the treadmill for all the crew members so now we'll have two treadmills up there," Shireman said.
NASA is seeking to maximize the shuttle flights to complete assembly of the ISS before the three US shuttle crafts are phased out of service in September 2010.
Shannon said that the agency is on schedule to end the shuttle program by the end of 2010.
"If we planned for more flights there will be significant work to re-start the process," he warned, adding that in October "we have the lay off of 1,200 shuttle employees -- that's 10 percent of my workforce."
Discovery is scheduled to liftoff from the Kennedy Space Center in Cape Canaveral, Florida at 1:36 am local time (0536 GMT) on August 25.
On its last mission, the shuttle Endeavour lifted off from Cape Canaveral on July 15 on its sixth attempt, delayed by bad weather and technical glitches.
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