Foam Mishap Won't Delay Shuttle Launch

Steven W. Lindsey leads the seven-member Discovery crew. (AP)

Discovery, pointed skyward on Launch Pad 39B at the Kennedy Space Center, is set for a 12-day mission to the international space station, where it will repair station machinery, test shuttle equipment and deliver supplies to station Commander Pavel Vinogradov and Flight Engineer Jeffrey Williams.

Shuttle Commander Steven W. Lindsey and the rest of Discovery's seven-member crew spent Monday resting up from two weekend launch attempts, both scrubbed because of bad weather.

Air Force 1st Lt. Kaleb Nordgren of the Weather Squadron said the chances of launch Tuesday would improve to 60 percent, relatively good for midsummer Florida afternoons, when thunderstorms are the norm. The odds will drop back to 40 percent Wednesday.

Launch Director Michael D. Leinbach scrubbed Sunday's attempt earlier than necessary to get a head start on replenishing Discovery's onboard fuel cells with liquid hydrogen, used to run the shuttle's electrical systems. The hydrogen gradually boils off as the shuttle waits on the launch pad.

Immediately after the scrub, shuttle technicians also began emptying the external fuel tank of 500,000 gallons of liquid hydrogen and liquid oxygen, a regular procedure between launch attempts.

After the "detanking," the ice team spotted the crack on foam insulation on the bracket for the liquid-oxygen feed line. The bracket strut, high on the side of the fuel tank, moves as the tank expands and contracts when fuel is pumped in or removed. The liquid hydrogen is cooled to minus 423 degrees Fahrenheit, and the liquid oxygen combuster is at minus 297 degrees Fahrenheit.

John Chapman, head of the External Tank Project Office at NASA, said Sunday's mishap probably occurred as the bracket was expanding with the removal of the cryogenic fuels. Rainwater from the day's periodic cloudbursts had probably collected in the bracket, he said, and when liquid oxygen was running through the feed line, the water turned to ice, crushing the piece of foam.

When the foam tried to expand as it warmed, he said, the ice cracked it.