Fuel Tank Repairs Enter Second Phase for Shuttle Atlantis

Workers apply foam and molds on the shuttle Atlantis' external tank to areas damaged by hail. The white hole with a red circle around it (upper right) is a hole prepared for molding and material application. The red material is sealant tape so the mold doesn't leak when the foam rises. The white/translucent square mold is an area where the foam has been applied and the foam has risen and cured against the mold surface. CREDIT: NASA/George Shelton.

CAPE CANAVERAL - NASA set out Tuesday on a second phase of repairs to shuttle Atlantis' hail-battered external tank, work that will determine whether the agency can resume International Space Station construction as planned in early June.

Normally done with robotics in the factory, the unprecedented work requires technicians to spray an aerodynamically smooth layer of thermal insulation on the curved portion near the top of the bullet-shaped tank.

Engineers built mock-ups and developed step-by-step procedures to prepare for the high-precision repairs, and technicians practiced manual sprays. NASA has never flown a tank repaired with this technique.

"There's a lot of confidence that everything is going to go smoothly," said June Malone, a spokeswoman for NASA's Marshall Space Flight Center in Huntsville, Ala.

The work is critical to NASA's plans to launch Atlantis and seven astronauts around June 8 on a mission to deliver a new 17.5-ton truss segment to the international outpost.

The launch had been scheduled for March 15 but was postponed when the shuttle's 15-story tank sustained serious damage during a Feb. 26 hailstorm.

Technicians already have fixed more than 2,100 of some 2,600 dents, divots and gouges in foam insulation covering the central and lower portions of the tank.

NASA also is inspecting the orbiter's main propulsion system propellant lines in an effort to spot any contamination that could trigger an engine failure in flight.

The inspections follow the discovery of four small pieces of silicon rubber within one of the three main engines that flew on a shuttle last December. Debris in a propellant line could degrade engine performance or, in a worst case, lead to a catastrophic failure in flight.

Engineers are using snake-like devices tipped with cameras.

The tank repairs and engine inspections are scheduled to be complete before the shuttle returns to launch pad 39A around May 15. About 22 days of routine launch preparations are required at the pad, so the schedule for a June 8 flight is tight.

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