HOUSTON -- Spacewalking astronauts will not have to perform an unprecedented spacewalk repair to fill in a gouge on their orbiter's belly-mounted heat shield, mission managers said late Thursday.
After a week of intense scrutiny and a battery of tests, mission managers concluded that the small, but deep, divot in Endeavour's undercarriage will not require repair during a planned Saturday spacewalk, said John Shannon, chairman of NASA's STS-118 mission management team.
"We went through all of that data and it was unanimous that we were not in a loss of crew vehicle case," Shannon told reporters in a briefing here at the Johnson Space Center (JSC).
There was some dissent from one NASA branch, the JSC Engineering Group that serves as one of three independent entities to check the agency's work, which stated it would be "prudent" to patch Endeavour's dinged tile, but otherwise the group found flying as is acceptable, Shannon said.
The decision clears Endeavour and its seven-astronaut crew for a planned Aug. 22 landing, pending a now-standard late inspection of the orbiter's wing edges and nose cap, once the orbiter casts off from the International Space Station (ISS) on Monday.
"I am 100 percent comfortable that the work that has been done has accurately characterized it, and that we will have a very successful reentry," Shannon said of the tile damage, adding that, had the analysis favored repair he would have been equally as comfortable.
A baseball-sized piece of foam insulation weighing 0.021 pounds (about one-third of an ounce) popped free from Endeavour's external fuel tank about a minute after its Aug. 8 launch.
The debris bounced off a metal strut and smacked into Endeavour's belly-mounted tiles, leaving a small, deep pit that exposed a slim one-inch (2.5-centimeter) long strip of felt covering the shuttle's aluminum skin. The 3 1/2-inch (nine-centimeter) long gash sits about four feet (1.2 meters) aft of Endeavour's right landing gear door. During reentry and landing, temperatures can reach between 2,000 and 2,100 degrees Fahrenheit (1,093-1,148 degrees Celsius) in that area.
But the damage, NASA said, is not a threat to the safe return of Endeavour's STS-118 astronaut crew, nor will the heating during reentry exceed the orbiter's safety margins, mission managers said.
"They seem to feel that the biggest danger is more just being able to reuse Endeavour once we get back on the ground," STS-118 mission specialist Alvin Drew, Jr. told reporters Thursday. "They seem to be confident, and I trust their confidence, that we can get home safely even with the divot that we have in the belly."
Shuttle flight controllers did draw up a possible two-part repair to fill in the tile gouge that would call on spacewalkers Rick Mastracchio and Dave Williams to perch themselves at the tip of the shuttle's 100-foot (30-meter) robotic arm and inspection boom.
Once there, they would swing behind Endeavour's underbelly, coat the dinged tiles with a heat-resistant paint and then fill the divot with a caulk-like ablative goo known as STA-54 while taking extreme care not to cause additional damage to the shuttle's heat shield.
"It is not appropriate, if you have a condition that is acceptable, to expose the crew to that risk," Shannon said.
NASA developed the inspection boom and both repair techniques after its fatal 2003 Columbia catastrophe, but only the paint fix - known as an emmitance wash - has been tested in space.
Plans for the fix were relayed up to the astronauts early Thursday, but Mission Control warned the shuttle crew that it was entirely possible a repair would not be needed.
"Please pass along our thanks for all the hard work certainly to the MMT, but also to everyone supporting our flight," shuttle commander Scott Kelly said of Endeavour's mission management team (MMT).
With no tile repair required, Williams and ISS flight engineer Clayton Anderson will now prepare for Saturday spacewalk to continue assembly of the orbital laboratory. NASA engineers are drawing up new routes across the ISS exterior to avoid regions with sharp edges that could damage spacesuit gloves after a small hole in one of Mastracchio's gloves forced an early end to a Wednesday excursion.
NASA is broadcasting Endeavour's STS-118 mission live on NASA TV. Click here for mission updates and SPACE.com's NASA TV feed.
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