After
months of unprecedented repairs, the ding-ridden fuel tank of NASA's space shuttle
Atlantis is patched up and primed for a planned June 8 launch, top agency
officials said Friday.
"I'm really
pleased to say that we have effectively completed the repairs on the external
tank," Wayne Hale, NASA's shuttle program manager, told reporters in a
teleconference.
The
announcement kick-starts Atlantis' stalled STS-117 mission more than two months
after a Feb. 26 storm battered
the orbiter's foam-covered external tank with hail at its Pad 39A
launch site at NASA's Kennedy Space Center (KSC) in Florida.
Launch
pad bound
Atlantis is
slated to launch no earlier than June 8, and is due to return to the launch pad
at 4:00 a.m. EDT (080 GMT) on May 16, NASA officials said. The shuttle could
leave its makeshift repair site -- NASA's cavernous Vehicle Assembly Building at
KSC -- a day early if scaffoldings are removed in time over the weekend, they
added.
"As you can
imagine, it's going to look pretty speckle-y," John Chapman, NASA's external tank
project manager, told reporters during the briefing. "It's kind of like having
a car that has had body and fender work, but hasn't had the primer work...you're
eye has trouble recognizing that it's going to be nice and smooth."
All tests
to date have found the fixes sound for NASA's upcoming shuttle flight, though
the sheer scope of the repair work does add some risk to the upcoming launch, mission
managers said.
"There is,
at least mathematically, some small increase in risk," Hale said. "But our work
indicates that that is a very small-to-nonexistent increase to the potential
for damage."
NASA has
kept a close eye on shuttle fuel tank foam and made a series of improvements
since the 2003 Columbia
accident, in which an errant chunk of insulation tore free from its tank
during liftoff and struck the orbiter's heat shield, leading to loss of the
spacecraft and its seven-astronaut crew during their return to Earth.
Round-the-clock
repairs
Commanded by
veteran spaceflyer Rick Sturckow, Atlantis' STS-117 astronaut crew will deliver
a new pair of solar arrays to the International Space Station (ISS) and ferry
NASA astronaut Clayton Anderson to replace fellow U.S. spaceflyer Sunita
Williams as a member of the orbital laboratory's Expedition 15 crew.
The ISS
construction flight was initially headed for a March 15 launch target when a
freak storm pelted the orbiter and its fuel tank with hail the size of golf
balls on Feb. 26. The hailstones gouged some 4,200 divots into the vital foam
insulation coating Atlantis' fuel tank, prompting almost three months of delays
to make repairs.
"This team
has been essentially working 24/7 since the storm doing engineering analysis,
testing and repair of the tank," Chapman said. "This has truly been unique. We've
had hail damage before, but never to this magnitude."
Repair
crews stripped away whole sections around the fuel tanks nose cap, where hail had
gouged about 1,400 divots into the foam surface, then sprayed the area with new
insulation, NASA said. Nearly 2,800 other small dings were repaired with a
variety of other methods.
"Each and
every one of those sites required detailed engineering analysis and
disposition," Chapman said.
To do that,
engineers pelted samples of shuttle fuel tank foam with steel balls to simulate
hail damage, then patched them up and tested them in a hot gas chamber to
ensure the fixes were safe for Atlantis' actual tank.
Sharper
sander
Repair
crews also developed a new, but vital, tool to re-contour the nose cap foam of
Atlantis' fuel tank to the proper shape to withstand aerodynamic stresses and
heating during liftoff, Chapman said.
During construction
at NASA's Michoud Assembly Facility in New Orleans, Louisiana, shuttle fuel
tanks are rotated under a sanding device to shave away excess nose cap foam in
a pencil-sharpening fashion. Since Atlantis' fuel tank is attached to the
orbiter at KSC, engineers developed
a portable sanding machine that could perform the same contour work inside
the VAB.
Hale lauded
the efforts of NASA engineers and contractors from across the agency for their
ability to focus given a tumultuous few months that have seen a former astronaut
arrested, freak storms, a shooting at the agency's Johnson Space Center in
Houston and most recently two
consecutive train derailments that plagued a shipment of shuttle rocket
booster segments to KSC.
"They have
shown real American grit in the face of adversity," Hale said.
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