After a successful simulated launch countdown, STS-128 astronauts (from left) Danny Olivas, Nicole Stott and Christer Fuglesang settle in the slidewire basket on NASA Kennedy Space Center's fixed service structure. They are practicing emergency exit from the pad on Aug. 7, 2009.
Credit: NASA/Kim Shiflett.
An external tank foam-shedding problem could prompt NASA to roll shuttle Discovery back to Kennedy Space Center's assembly building for repairs, but the agency still is pressing ahead with preparations for the targeted Aug. 25 launch.
Senior NASA managers will gather today and Wednesday for a preliminary flight readiness review for Discovery, which is slated to fly seven astronauts on an International Space Station outfitting mission.
One key issue to be addressed: significant foam loss on NASA's past two flights from metal brackets that hold liquid oxygen pressurization lines and electrical cabling on the side of the shuttle's 15-story external tank.
"I suspect there will be a good deal of discussion about this," said Kyle Herring, a spokesman for NASA's Johnson Space Center in Houston.
NASA is facing a Sept. 3 deadline to launch or delay the mission until October. A robotic Japanese cargo carrier is scheduled to launch on its debut mission to the station on Sept. 10 and Russia is set to launch a crew exchange mission to the outpost around Sept. 20.
A recommendation to fly Discovery as is or roll the shuttle back to the Vehicle Assembly Building for repairs will be made on Aug. 18.
Here's the situation:
Larger-than-allowable chunks of foam insulation broke free from a so-called ice frost ramp during the launches of Atlantis in May and Endeavour in July.
On the Endeavour flight, foam chunks that weighed about 0.044 pounds -- or about double the allowable amount -- broke free from a bracket high up on the shuttle's bullet-shaped tank.
The concern is that breakaway foam could do critical damage to shuttle wing panels or thermal tiles, which protect orbiters and astronauts from extreme heat during atmospheric reentry.
Columbia and its seven-member crew were lost in 2003 when a 1.67-pound chunk of foam broke free 81 seconds into flight, blasting a 6- to 10-inch hole in its left wing.
Hot gases blowtorched through the hole during atmospheric reentry, leading to the disintegration of the spaceship 16 minutes before a planned landing here at KSC.
Endeavour's tank also shed an unusual amount of thin foam from a ribbed center section during its July 15 launch. NASA engineers say an adhesive failed to bond properly with a substrate primer on the aluminum lithium skin of the tank.
More than 150 tests were performed on that area of Discovery's tank prior to its move last week to launch pad 39A. That problem is not expected to delay Discovery's launch.
NASA engineers still are trying to determine the root cause of the foam loss from the ice frost ramps. Each tank is equipped with 34 of the metal support brackets. Foam insulation applied to them smoothes airflow over the brackets and prevents ice build-ups.
Herring said the suspect ramp on Discovery's tank has no known flaws. Special high-tech x-rays uncovered no cracks or voids during extra testing prior to Discovery's move to the pad, he said.
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