NASA: No Heat Shield Repair Required for Shuttle Endeavour

NASA 'Cautiously Optimistic' Shuttle Repair Not Required
This image of the gouge to heat shield tiles on the space shuttle Endeavour was taken Aug. 12, 2007 using a camera on an extension boom during a focused inspection by the orbiter's crew.
(Image: © NASA.)

HOUSTON --Spacewalking astronauts will not have to perform an unprecedented spacewalkrepair to fill in a gouge on their orbiter's belly-mounted heat shield, missionmanagers said late Thursday.

After a week ofintense scrutiny and a battery of tests, mission managers concluded thatthe small, but deep, divot in Endeavour's undercarriage will not requirerepair during a planned Saturday spacewalk, said John Shannon, chairman ofNASA's STS-118 mission management team.

"Wewent through all of that data and it was unanimous that we were not in a lossof crew vehicle case," Shannon told reporters in a briefing here at theJohnson Space Center (JSC).

There wassome dissent from one NASA branch, the JSC Engineering Group that serves as oneof three independent entities to check the agency's work, which stated it wouldbe "prudent" to patchEndeavour's dinged tile, but otherwise the group found flying as isacceptable, Shannon said.

Thedecision clears Endeavour and its seven-astronaut crew for a planned Aug. 22landing, pending a now-standard late inspection of the orbiter's wing edges andnose cap, once the orbiter casts off from the International Space Station (ISS)on Monday.

"I am100 percent comfortable that the work that has been done has accuratelycharacterized it, and that we will have a very successful reentry,"Shannon said of the tile damage, adding that, had the analysis favored repairhe would have been equally as comfortable.

Abaseball-sized piece of foam insulation weighing 0.021 pounds (about one-thirdof an ounce) popped free from Endeavour's external fuel tank about a minuteafter its Aug. 8 launch.

The debrisbounced off a metal strut and smacked into Endeavour's belly-mounted tiles, leavinga small, deep pit that exposed a slim one-inch (2.5-centimeter) long stripof 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 landinggear door. During reentry and landing, temperatures can reach between 2,000 and2,100 degrees Fahrenheit (1,093-1,148 degrees Celsius) inthat area.

But thedamage, NASA said, is not a threat to the safe return of Endeavour's STS-118astronaut crew, nor will the heating during reentry exceed the orbiter's safetymargins, mission managers said.

"Theyseem to feel that the biggest danger is more just being able to reuse Endeavouronce we get back on the ground," STS-118 mission specialist Alvin Drew,Jr. told reporters Thursday. "They seem to be confident, and I trust theirconfidence, that we can get home safely even with the divot that we have in thebelly."

Shuttleflight controllers did draw up a possible two-part repair to fill in the tilegouge that would call on spacewalkers Rick Mastracchio and Dave Williams toperch themselves at the tip of the shuttle's 100-foot (30-meter) robotic armand inspection boom.

Once there,they would swing behind Endeavour's underbelly, coat the dinged tiles with aheat-resistant paint and then fill the divot with a caulk-like ablative gooknown as STA-54 while taking extreme care not to cause additional damage to theshuttle's heat shield.

"It isnot appropriate, if you have a condition that is acceptable, to expose the crewto that risk," Shannon said.

NASAdeveloped the inspection boom and both repair techniques after its fatal 2003 Columbia catastrophe, butonly the paint fix - known as an emmitance wash - has been tested in space.

Plans for thefix were relayed up to the astronauts early Thursday, but Mission Controlwarned the shuttle crew that it was entirely possible a repair would not beneeded.

"Please pass along our thanks for all the hard workcertainly to the MMT, but also to everyone supporting our flight," shuttlecommander Scott Kelly said of Endeavour's mission management team (MMT).

With notile repair required, Williams and ISS flight engineer Clayton Anderson willnow prepare for Saturday spacewalk to continue assembly of the orbitallaboratory. NASA engineers are drawing up new routes across the ISS exterior toavoid regions with sharp edges that could damage spacesuit gloves after a smallhole in one of Mastracchio's gloves forced an earlyend to a Wednesday excursion.

NASA isbroadcasting Endeavour's STS-118 mission live on NASA TV. Click here for mission updates andSPACE.com'sNASA TV feed.

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