New foam covers fashioned for Discovery tank

NASA is equipping the external tank for its next shuttle mission with new foam covers after finishing a weekend effort to remove cracked covers from metal brackets on the exterior of the giant fuel reservoir.

Working in the checkout cell in the northwest corner of the Kennedy Space Center Vehicle Assembly Building, technicians removed foam-and-cork covers from four of five metal brackets that hold a 17-inch liquid oxygen feedline to the side of the tank being readied for the planned Oct. 23 launch of Discovery on an International Space Station assembly mission.

The covers are designed to keep ice from building up on the aluminum brackets when supercold propellants are loaded into the 15-story tank. The liquid oxygen that runs through the feedline is Minus 298 degrees Fahrenheit.

Hairline cracks were found in the four thermal covers, which are fashioned from two different types of foam and Super Lightweight Ablator (SLA). The SLA is a cork mixed with an epoxy bonding material.

Concerned that the cracks might lead to foam shedding in flight, NASA managers ordered up replacements late last week. The new thermal covers will be made from foam; the higher density cork will be left out of the mix.

Technicians started the replacement work today. The effort is expected to take the better part of the next two weeks.

NASA and contractor managers will meet today to refine the work schedule, but it appears the tank will be ready to be mated late next week to twin solid rocket boosters stacked on a mobile launcher platform in High Bay 1 of the assembly building.

Discovery and a crew of seven astronauts will deliver the U.S. Harmony module to the international station. Built in Italy, the multiport module will serve as the gateway between the U.S. section of the station and European and Japanese science laboratories to be launched late this year and in 2008.

Designated STS-120, the 13-day mission will be the 23rd station assembly mission to be flown by NASA's shuttle fleet. The crew includes mission commander Pam Melroy, pilot George Zamka and four mission specialists: Scott Parazynski, Douglas Wheelock, Stephanie Wilson and Paulo Nespoli of the European Space Agency.

U.S. astronaut Dan Tani will taxi up to the station on Discovery, and current station flight engineer Clay Anderson will return to Earth on the shuttle.

IMAGE NOTE: Click to enlarge the NASA image of ET-120 being hoisted off a transporter in the transfer aisle of the Kennedy Space Center Vehicle Assembly Building in late July. The tank now is in the checkout cell in the northwest corner of the building, where modifications are being made to thermal covers on metal brackets that hold a liquid oxygen feedline on the side of the tank. Photo credit: NASA/George Shelton.