NASA is targeting an early June launch for its space shuttle Atlantis and will complete repairs to the orbiter's hail-battered external fuel tank rather than replace the 15-story vessel with a pristine one, mission managers said late Tuesday.
Atlantis and its six-astronaut crew are now slated to launch towards the International Space Station (ISS) no earlier than June 8 to deliver new starboard solar arrays and girders to the orbital laboratory.
"As of right now we're going to stay with the tank," said NASA shuttle program manager Wayne Hale of Atlantis' pockmarked fuel tank during a teleconference late Tuesday. "The entire team unanimously agreed that progress was being made to do that."
Hale said that the ongoing repair work to Atlantis' fuel tank would allow the orbiter to leave the cavernous Vehicle Assembly Building at NASA's Kennedy Space Center (KSC) in Florida and return to its launch pad around May 6, but that would not allow the orbiter and its STS-117 crew to launch within the limited flight window that closes on May 21.
Since the repair work was making progress, and replacing the Atlantis' fuel tank with a new one would push the orbiter's launch date to no earlier than June 19, mission managers opted to keep the current fuel tank, Hale added.
The new launch window stretches from June 8 to about July 18, with the next flight opportunity occurring around Aug. 5, NASA officials said.
Atlantis' STS-117 mission has been delayed since Feb. 26, when a severe thunderstorm battered the orbiter's fuel tank with golf ball-sized hail at its launch pad just weeks shy of a planned March 15 liftoff. The hail gouged more than 2,600 dings in the vital foam insulation covering the fuel tank.
Since that freak February storm, which appeared to occur right over Atlantis' Pad 39A launch site, engineers have been hard at work sanding the tank's surface and filling in divots with new foam, while another team analyzes the fixes to ensure they are sound.
Repair work underway
John Honeycutt, head of NASA's external tank project, said there are some 2,664 damaged areas on Atlantis' external tank. About 700 of them require workers to pour new foam insulation into the divots, a task that is about half complete, he added. Other areas will require a sand and blend approach, while still others may require a spray technique.
Shuttle workers are also removing the Atlantis' three main rocket engines to inspect its propellant lines for silicone contamination akin to that found in the propellant lines of Atlantis' sister ship Discovery, NASA officials said, adding that the work is not expected to affect the orbiter's launch date.
Commanded by veteran shuttle flyer Rick Sturckow, Atlantis' six-astronaut crew is gearing up to install the 17.5-ton Starboard 3/Starboard 4 trusses and twin solar arrays during three spacewalks planned for their 11-day mission. He and his crew have used their extra time on Earth to continue their mission training and spend time with family and friends.
"They're taking it in good spirits," Hale said of the STS-117 crew. "They want to have a good safe launch vehicle."
Atlantis' launch delay does mean that one NASA astronaut, spaceflyer Sunita Williams currently aboard the ISS, will have to wait a bit longer to return to Earth.
Williams was scheduled to return home aboard NASA's Endeavour orbiter during the STS-118 mission in July. Atlantis' launch slip to June pushes Endeavour's planned liftoff to early August, though Williams remains on schedule to return to Earth with the STS-118 crew.
"Right now we're staying with the current scenario," William Gerstenmaier, NASA's associate administrator for space operations, told reporters.
Williams could conceivably come home earlier aboard Atlantis, which would then bring NASA astronaut Clayton Anderson as a replacement, if the STS-118 flight slipped deep into fall, Gerstenmaier added, but stressed that it is not the current plan.
An eye on foam
The layers of foam insulation covering a shuttle's external tank prevent the vessel's super-cold load of liquid hydrogen and liquid oxygen propellant from building up ice on its aluminum exterior, NASA officials have said. Some foam at the tank's nose provides protection from aerodynamic stresses during launch, they added.
The foam's integrity has been a prime concern since the 2003, when an errant chunk of tank foam fell free during the launch of NASA's Columbia orbiter, piercing its left wing leading edge heat shield and leading to the loss of the shuttle and its seven-astronaut crew as they reentered the Earth's atmosphere.
NASA has since made a series of modifications to shuttle fuel tanks to eliminate foam where possible and limit the amount of material shed during launch. Shuttle and ISS astronauts also perform meticulous robotic and photographic inspections of an orbiter's heat shield while in space.
Atlantis' STS-117 mission is expected to be the first of about four planned NASA shuttle missions to continue ISS assembly in 2007. NASA hoped to squeeze in a fifth shuttle flight during December, though mission managers have said that spaceflight will likely slip to 2008. Even launching four shuttle flights this year may prove challenging, they added.
"I would say that flying four flights is not outside the realm of possibility," Hale said. "But we want to do this in a safe and orderly manner."
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