NASA has decided to proceed with a shuttle launch to the International Space Station (ISS) next week, having concluded that insulation foam losses from the external fuel tank, which occurred during the two previous shuttle launches, did not pose an unacceptable risk to the upcoming mission.

Space shuttle Discovery is set to lift off early Tuesday morning from Kennedy Space Center in Florida on a 13-day mission to the ISS. Discovery will deliver to the station new science gear and additional life-support equipment, as well as Stephen Colbert's namesake exercise device, the COLBERT treadmill.

There was much concern about the safety of the foam insulation that coats the shuttle's external fuel tank. Orbiters in both a May mission to the Hubble Space Telescope and last month's mission to the ISS showed dings from falling pieces of foam during ascent. A large-scale foam loss significantly damaged the heat shield of space shuttle Columbia in 2003, and the shuttle broke up on reentry, killing all seven crewmembers.

"We had lots of discussion about the foam," NASA associate administrator for space operations Bill Gerstenmaier said in a morning news conference today at Kennedy Space Center. And although there were differences of opinion on how to interpret the data from foam tests, Gerstenmaier said, the discussion was not contentious. "No one chose to appeal the decision" to fly, he said.

Space shuttle program manager John Shannon put the issue in perspective, saying that the foam loss on last month's mission was one-fiftieth the mass of the foam loss that doomed Columbia. "I think we have done due diligence on the foam," he said.

Photo of the shuttle crew heading for a simulated launch countdown earlier this month: NASA/Kim Shiflett