NASA's PAL Ramp Foam Problem a Lesson in Failure, Shuttle Chief Says

LAKE BUENAVISTA, Fl. -- NASA's efforts to address foam debris issues with its shuttlefuel tanks has proven an object lesson of how even the most diligentspaceflight risk management efforts can fail, the agency's shuttle chief saidWednesday.

Wayne Hale,NASA's shuttle program manager, told about 400 risk experts, engineers andmanagers that the loss of a one-poundchunk of foam from a protuberance air load (PAL) ramp during the Discoveryorbiter's STS-114 launch wasnot among the top risks expected for the mission before flight.

"Ourmistake was that we thought we understood the mechanism for foam loss," Halesaid here during NASA's Risk Management Conference 2005, adding that the PAL foamfell well clear of Discovery. "We were lucky."

The foamloss was reminiscent of a similar problem that doomed the space shuttle Columbia and its crew, andmarred Discovery's otherwise successful flight to the International SpaceStation (ISS).

Engineersmay now decide to removePAL ramps altogether from an external tank to fuel NASA's next shuttlelaunch, Discovery's STS-121 flight, set to fly no earlier than May2006. A meeting to discuss the matter could be held next week, Hale told SPACE.com.

STS-114pilot James Kelly said that while external tank foam debris was critical issuebefore the flight, he and his crewmates were more interested in ensuring theirspacecraft's integrity.

"The mostcritical thing for us as a crew was knowing the healthof our vehicle," Kelly said during the conference. "If you don't know there'ssomething to fix, it doesn't matter how well you can fix it."

NASA'sSTS-114 flight carried a 50-foot (15-meter) boomextension for the orbiter's robotic arm. Tipped with laser sensors and acamera, the boom allowed Kelly and his fellow Discovery astronauts to scan theorbiter's heat shield in flight and send the data down to engineers who latercleared the shuttle for reentry.

Kelly saidthe STS-114 crew did receive a good lesson in determining risk trade-offs whilepreparing for Discovery's flight.

The lack ofa backup system to ensure that latches for stowage lockers remained closedduring launch required the use of tape to safe their doors, he said, addingthat the STS-114 crew also traded a series of exchanges with structuralanalysts to develop contingency plans for securing a 600-pound (272-kilogram)ISS gyroscope in Discovery's payload bay for return to Earth.

Kelly saidSTS-114 mission managers did overrule Discovery's crew when it came to adding apair of heat shield repair tools on the orbiter's launch manifest. Two cure-in-place-ablative-applicators(CIPAA), backpack-mounted tools designed to squirt a pink goo-likematerial into damage tiles, rode aboard Discovery even though the repair methoditself was not ready for orbital testing.

"Our crewnever expected to have it onboard...[but] people did notwant to send us on orbit without something to save us, it was a very emotionalissue," Kelly said, adding that the important thing was that Discovery'sastronaut crew voiced their opinions. "Our concerns were noted and I think thatwas a success story."