NASA wrestled Monday with whether to try a Fourth of July space shuttle liftoff after the startling discovery of a small chunk of foam insulation that broke off Discovery's fuel tank as it sat on the launch pad.

The troubling find came after inspectors discovered a 5-inch-long crack in the foam, a problem that continues to vex NASA ever since a big piece of foam brought down Columbia and killed seven astronauts in 2003.

A graphic from NASA shows the external fuel tank, close-up of the lock speedline bracket showing an area of missing foam and a photo of the missing chunk of foam from space shuttle Discovery's external fuel tank in Cape Canaveral July 3, 2006. [Reuters]

NASA managers were meeting Monday evening to decide how to tackle the problem and whether a Tuesday launch was possible.

At least one member of the panel of experts that investigated the Columbia accident said he was nervous about the decision.

"If those guys aren't more nervous than I am, they've become jaded and should resign their positions," said Nobel Prize-winning physicist Douglas Osheroff. But two of Osheroff's accident board colleagues said they were comfortable, with board chairman Harold Gehman Jr. saying, "It looks to me like they are following the right decision processes."

NASA managers are leaning toward flying Discovery with no changes to the foam section in question, said John Chapman, external tank project manager.

The other options were to spend a day inspecting the foam area of concern, which would push the launch back to Wednesday, or to try to fix the foam, which would take several days and require NASA to use a new technique since such a repair has never been done in that area before, Chapman said.

"We believe we're getting much more comfortable with the ability to potentially fly as we are right now, but the team is still looking at that," Chapman said. "We want to make sure that we understand all the considerations that caused this foam to be lost."

The 3-inch-long, triangle-shaped piece fell off an area of foam that covers an expandable bracket holding a liquid oxygen fuel line against the huge external tank. NASA engineers believe ice built up in that area from condensation caused by rain Sunday.

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