NASA readies for third attempt to launch shuttle

By Deborah Zabarenko

CAPE CANAVERAL, Florida (Reuters) – NASA counted down on Tuesday to a third attempt to launch space shuttle Discovery on a mission vital to the program’s future after easing worries over a crack in foam insulation on the ship’s fuel tank.

Bad weather canceled planned launches on Saturday and Sunday, but NASA forecasters said there was an 80 percent chance of favorable weather on this U.S. Independence Day, the best prediction so far in this launch window.

The flight, set to lift off at 2:38 p.m. EDT (1838 GMT) from the Kennedy Space Center in Florida, is critical to NASA’s plan to finish the half-built International Space Station before the fleet is retired in 2010. An accident or serious problem likely would ground the shuttles permanently.

A small crack in the foam that insulates Discovery’s massive external tank raised concerns on Monday, and NASA experts inspected the area early on Tuesday to see if any potentially damaging ice had formed in the area of the crack. None had, according to NASA flight commentator George Diller.

"That is good news, that there has not been any ice buildup in that area where the insulation was lost," Diller said.

A circuit breaker problem relating to the shuttle’s booster joint heaters prompted NASA to assemble a repair team to send to the launch pad, but commentator Bruce Buckingham said, "The system is functional at this time and we could fly as is."

Problems with falling foam insulation have been a key concern for NASA since the fatal disintegration of shuttle Columbia on February 1, 2003. That accident was caused by a briefcase-sized chunk of foam that hit Columbia’s left wing on launch, opening a hole that let in superheated gas during re-entry, killing all seven crew.

TROUBLE-SHOOTING

Despite extensive investigation, trouble-shooting and new design features, the problem recurred a year ago during a launch of Discovery. It forced NASA to ground the shuttle fleet while engineers worked on more modifications.

Even before this latest problem with foam, NASA administrator Michael Griffin had decided to proceed with the current launch over objections of his chief engineer and head of safety.

But there was no dissent over the immediate problem of the cracked foam insulation.

"I think the teams have done a very good job of avoiding … launch fever," NASA’s associate administrator for spaceflight, Bill Gerstenmaier, said late on Monday after managers decided the small foam crack along an oxygen fuel line was not a launch hazard.

Inspectors discovered the 5-inch long, 1/2-inch wide crack in the fuel tank foam following the second launch attempt on Sunday. A small wedge of foam broke away and was found on the launch platform.

The crack was probably caused by condensation trailing down the shuttle’s liquid oxygen fuel line and then freezing due to the extreme cold of the fuel flowing through the pipe. When the fuel tank was emptied after Sunday’s delay, the ice melted and the foam cracked as the line expanded in the warm air.

Kennedy Space Center technicians used a tiny camera encased in flexible plastic to get detailed, close-up pictures of the crack and surrounding area, and those images showed the rest of the foam was in good shape.

Engineers expect small amount of ice will form in the crack, but not enough to pose a debris hazard to Discovery.

The shuttle will head toward the space station to deliver equipment and supplies, make repairs to a mobile rail cart, and deliver a new crewmember. Since the Columbia accident, the station has been operated by two crew to save on supplies.

The primary goal of NASA’s 115th shuttle mission, however, is to test the new tank design and other safety upgrades.

(Additional reporting by Jim Loney and Irene Klotz)