Thursday, July 23, 2009

Additional tests planned for Discovery tank

Additional tests to the external fuel tank set to fly with Discovery next month will push the launch date back at least four or five days.

A first round of 26 foam samples from the tank's "intertank" area did not show signs of problem with its adhesion.

But engineers today agreed that a larger number samples was needed to achieve a statistically useful result.

Starting Friday, workers on scaffolding in Kennedy Space Center's Vehicle Assembly Building will begin pulling an additional 125 "plugs" of foam from the intertank, all from the side that faces away from the orbiter.

"It's like coring an apple," said Kyle Herring, a NASA spokesman at the Johnson Space Center in Houston, describing the testing technique. "It's like a high-tech cookie cutter."

Discovery was tentatively scheduled to roll from its processing hangar to the 52-story VAB on Friday, where it would be mated with the tank and twin solid rocket boosters on a mobile launcher platform.

Now that will happen Sunday at the earliest. Discovery's launch, most recently targeted for Aug. 21, will move to the 25th or 26th assuming the additional tests raise no new concerns, Herring said.

A standard foam repair technique will be used to fill in the areas where core samples have been taken.

NASA ordered up the tests after Endeavour's tank showed a surprising amount of shedding from the intertank, where foam loss is not usually seen, after its July 15 launch.

The intertank connects the tank's liquid hydrogen and liquid oxygen tanks, which hold fuel at extremely cold temperatures.

The foam loss mostly came after the critical first couple of minutes of flight, when foam impacts can cause more damage. A first round of inspections of Endeavour's heat shields showed no need for repairs.

Earlier today, Discovery mission specialist Jose Hernandez posted a note on Twitter about the possible launch delay: "Looks like our launch will slip. Most likely date is Aug 26th. However, this is just a rumor. Will post the new date once it is official."

You can link to his tweets here.

IMAGE NOTE: In the Vehicle Assembly Building's High Bay 1 at Kennedy Space Center, Eugene Sweet, a principal liaison engineer from NASA's Michoud Assembly Facility near New Orleans where the external fuel tanks are built, is testing foam adhesion on the intertank of space shuttle Discovery's external tank. He is collecting foam samples an inch-and-half in diameter for analysis to confirm the foam is bonded well to the metal primer underneath. The testing was prompted by the foam loss during launch of space shuttle Endeavour on the STS-127 mission July 15. Photo credit: NASA/Tim Jacobs.

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