NASA Eyes Space Shuttle Fuel Tank Fix
In the Vehicle Assembly Building at kennedy Space Center, the external tank which will be used for the October STS-120 space shuttle mission is being fitted with a crane to lift it into a checkout cell.
CREDIT: George Shelton/NASA
CAPE CANAVERAL, Fla. -- NASA is weighing the benefits of several possible modifications for space shuttle fuel tanks after a debris strike etched a deep gouge in the Endeavour orbiter's underbelly last week, a top shuttle official said Monday.
Wayne Hale, NASA's space shuttle program manager, said a team of engineers are studying up to five methods of tweaking fuel tank brackets to avoid the type of foam debris hit that dinged Endeavour.
"The all involve some reduction in the foam around the top of this little bracket," Hale told reporters in a Monday briefing.
A small piece of foam about the size of a baseball fell from a bracket on Endeavour's fuel tank roughly a minute after the shuttle's Aug. 8 launch. The shuttle is set to land later today here at the Kennedy Space Center.
The 0.021-pound (about one-third of an ounce) foam chunk, which may have contained some ice, unexpectedly ricocheted off a metal tank strut and gouged a deep, 3 1/2-inch by 2-inch (9-centimeter by 5-centimeter) long divot in the fragile heat-resistant tiles on Endeavour's belly.
"We didn?t think this could happen before," Hale, adding that previous studies predicted such foam debris would sweep harmlessly past an orbiter. "Clearly, we're smarter now than we were a couple of weeks ago."
While the resulting damage was later found to pose no risk to the safe return of the orbiter or its seven-astronaut crew, NASA has found similar foam shedding events on its last few shuttle flights. The damage from any such foam loss to an orbiter's heat shield is not believed to be catastrophic, like that which led to the 2003 Columbia accident, but engineers are analyzing it just to be sure, Hale said.
The increased frequency has prompted speculation that an extra hour added to launch countdowns - to allow inspections teams to scan shuttle fuel tanks for ice build-up - may actually contribute to ice formation that ultimately cracks or looses foam debris.
NASA engineers are already planning to replace the foam-covered brackets on fuel tanks, beginning with a planned April 2008 shuttle flight, but discussion is ongoing on whether an interim fix will be required. The space agency has continually worked to avoid foam debris during liftoff since a chunk of the insulation tore loose during the 2003 launch of Columbia and led to the orbiter's destruction during reentry.
LeRoy Cain, NASA's launch integration manager, told reporters last week that the space agency delayed today's planned mating of the next shuttle fuel tank to fly to its twin solid rocket boosters pending a final design change decision.
Trimming some unnecessary foam insulation from the brackets or coating them in slick solution or oil are among the possible modifications under discussion, he added.
Any fuel tank modification, if required, is not expected to add a major delay for NASA's planned Oct. 23 launch of the shuttle Discovery to deliver the new Harmony connecting node to the International Space Station.
"It's a serious problem for us, and we recognize right away that we need to go resolve it before we fly the next mission," Cain said.
But it could affect a planned December flight aboard Atlantis to haul the European Space Agency's Columbus laboratory to the station, Hale said. That flight has a slim, week-or-so long window that opens Dec. 6 in which to launch towards the space station, he added.
NASA has a relatively tight schedule of at least 11 more shuttle flights planned to complete space station construction by September 2010, when the agency's three-orbiter fleet is slated for retirement
Nevertheless, engineers will evaluate shuttle fuel tank safety between flights to identify what type of fix, if any, will be ultimately required, NASA said.
"It's just another day at the office," Hale said. "This is the kind of work that we're into if we want to fly this vehicle throughout its manifest."
NASA is broadcasting Endeavour's STS-118 mission live on NASA TV. Click here for mission updates and SPACE.com's NASA TV feed.
- VIDEO: STS-116 Mission Profile: Fourth Spacewalk
- VIDEO: Endeavour Shuttle Tile Damage
- Complete Space Shuttle Mission Coverage
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