MIAMI – Two scraps of insulation dangling from shuttle Discovery’s fuselage could pose a danger to the crew and might have to be removed or poked back into place during a spacewalk, mission managers said Sunday.

At issue in this latest complication confronted by NASA are two “gap fillers,” narrow strips of material that fill the space between the insulating tiles that protect the shuttle – and its seven astronauts – from the intense heat of reentry through the atmosphere.

Wayne Hale, NASA’s deputy manager of the shuttle program, said the astronauts were in no immediate danger and engineers were examining the problem and devising possible solutions.

“They’re working overtime to compress a decade worth of study into two days,” he said.

Asked about his gut feeling, he said he believed two Discovery spacewalkers likely will be asked to repair the craft in flight Wednesday.

“Why would you not take care of it if you have a simple plan to deal with it?” he said.

A breach in the protective skin, caused by an errant chunk of launch debris from the external fuel tank, caused the loss of shuttle Columbia and its seven crew members in February 2003.

Now, it has made NASA far more cautious.

“The Columbia accident caused us to realize that we’ve been playing Russian roulette with the shuttle crews,” Hale said candidly.

Discovery’s mission, the first since that accident, has been plagued by concerns over similar launch debris – concerns so intense that NASA again has grounded future missions and the agency’s chief openly admitted Sunday that engineers had failed in their task to modify the fuel tank.

“Our judgment at the time was that it was OK,” NASA Administrator Michael Griffin told NBC News. “As everyone has said without any attempt to hide it … we goofed on that one.”

Now, experts are concerned that the dangling scraps of insulation could affect Discovery’s aerodynamic performance as it returns next week to the Kennedy Space Center, possibly overheating part of the craft beyond its tolerances and causing another fatal accident.

“Technically, it increases the heating rate,” Hale said earlier during the mission. “I have heard the numbers on the order of a couple hundred degrees.”

Engineers plan to issue recommendations Monday.

One possibility: Adding new duties to the spacewalk scheduled for Wednesday, requiring the astronauts to trim away the protruding strips or shove them back into place. One sticks out about an inch; the other about six-tenths of an inch.

On the other hand, flight director Paul Hill said, engineers might decide that no harm will come to the shuttle if it lands as is.

Gap fillers have shaken loose before, he and others said, but the problem has never been identified during a mission.

NASA has devoted countless hours to unprecedented inspections of Discovery’s surface during this mission.

“This is the first time we have ever seen it in flight before reentry …” Hale said Sunday. “We’re really working at the limits of our understanding of aerodynamics, and that’s a problem.”

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