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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