Countdown is ‘go’ after shuttle wait

CAPE CANAVERAL, Fla. – NASA signed off Monday night on a Fourth of July shuttle liftoff despite worries about a piece of foam that popped off Discovery’s external fuel tank while the spacecraft sat on the launchpad.

“We’re go to continue with the launch countdown,” said Bill Gerstenmaier, NASA associate administrator, at a nighttime briefing.

The decision for today’s 11:38 a.m. PDT Tuesday liftoff of Discovery, which is headed for the International Space Station, was sure to stir more debate about whether the space agency was putting its flight schedule ahead of safety even though Gerstenmaier said “there were no dissenters … no concerns raised” at a meeting of managers.

The 3-inch triangular piece of foam that appeared to come from a 5-inch-long crack late Sunday or early Monday is far smaller than the foam chunk that brought down Columbia, killing seven astronauts in 2003.

Managers had spent most of Monday exploring the problem. NASA has spent millions of dollars trying to prevent foam from breaking off at liftoff, threatening the kind of damage it did to Columbia. Engineers were startled when foam broke off Discovery during last year’s mission, but it didn’t harm the shuttle.

The loss of foam from that area of the tank while on the launchpad is a rare occurrence, happening only once before, Gerstenmaier said.

The patch of foam fell off an area that covers an expandable bracket holding a liquid oxygen feed line against the huge external tank. NASA engineers believe ice built up in that area from condensation caused by rain Sunday.

Sunday’s launch was canceled because of the weather.

The size of the fallen foam was less than half the size of one that could cause damage, officials said.

NASA managers decided to go ahead with the launch attempt because of three criteria: They are confident enough foam still is on the bracket to prevent a large piece of ice from forming; that the area of foam where the piece dropped was still intact; and they don’t believe the area will be exposed to extreme heat during ascent.