NASA scientists say the second spacewalk may be needed to carry out more repairs. They have just made necessary repairs only to face yet another potential danger in a "poofed-out" insulation blanket under a cockpit window.
The same engineering team that spent the previous four days analyzing the gap fillers — ceramic-coated fabric set between heat-resistant tiles — is now trying to figure out whether the aerodynamic forces of reentry could cause a piece of the quilted blanket to come off and hit the spacecraft.
So far, analysts think that the biggest chunk that could come off during reentry would weigh 0.05 of a pound. But even that small piece could be trouble.
"In the worst case … you wouldn't like the result," N. Wayne Hale Jr., deputy manager of the shuttle program, was quoted as saying by Los Angeles Times.
Some experts are not surprised that the shuttles, which began flying in 1981, are showing signs of age.
"This has been a troubled spacecraft since the day it was built," said physicist Robert L. Park of the University of Maryland.
"It was built to reduce the cost of flying into space, but it has turned out to be the most expensive way possible."
The part of the insulating blanket sticking out is about 20 inches long by 4 inches wide.
Early engineering studies showed that if a piece of this section of blanket hit the craft near the tail, there could be structural damage.
Hale could not say whether such damage would be catastrophic. He said wind-tunnel and other tests were to be performed Wednesday night at several NASA centers.
The results will help determine whether NASA orders a fourth spacewalk to fix the problem or decides to leave the blanket alone.
"I am very hopeful we will be able to put this to rest" soon, Hale said.
The blanket is one of 32 that cover portions of the shuttle.
Although silica tiles protect most of Discovery, the lightweight blankets are used in places that don't receive as much heat during reentry.
The bulging blanket is just the latest problem to bedevil Discovery, which is the first shuttle to be launched since the 2003 loss of Columbia, which was damaged by a piece of foam that came off during liftoff and destroyed on reentry.
A large piece of insulating foam fell off Discovery's external tank during launch from Kennedy Space Center last week, embarrassing the space agency, which had labored for more than two years to prevent recurrence of such a problem.
Later on Thursday the Discovery crew is planning a moment of reflection to remember their colleagues killed during the last shuttle mission on board Columbia, in 2003, BBC informs.
Discovery is due to return to Earth on 8 August.
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