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.
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.
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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