ORLANDO, Fla. – The space shuttle will not launch again until March at the earliest because engineers need more time to figure out why foam keeps breaking off the ships’ external fuel tanks during flight, NASA announced Thursday.

The agency is considering various fixes, including removing and re-applying foam in one area that shed the largest piece of debris during the July 26 launch of shuttle Discovery.

But extensive evaluation and study are still needed, making any launch attempts this year impossible, said Bill Gerstenmaier, NASA’s associate administrator for spaceflight operations.

“We’re just starting to make sense of the data and understand where things are coming together,” he said.

Gerstenmaier spoke Thursday at a news conference along with agency administrator Michael Griffin, who responded to criticism this week of NASA’s management and engineering practices.

The critical comments became public Wednesday in the final report of a task group that monitored the agency’s return-to-flight effort after the 2003 Columbia disaster.

The group’s full report gave NASA mostly high marks for improving safety. But seven of the 26 members issued a harsh minority report concluding that the agency had failed to change fundamentally. NASA still accepts risks without understanding them or even knowing how to evaluate them properly, the group concluded.

Griffin said pushing the next shuttle mission to March is evidence that the agency is taking a conservative approach. While not addressing specific criticisms, he expressed confidence in his top shuttle managers.

Though Discovery’s tank shed foam, Griffin noted that fewer pieces of foam came off this tank than in previous launches.

Most of the pieces were small, but a nearly 1-pound chunk broke off a ramp on the tank that covers some cable trays and fuel lines. The large piece did not hit the orbiter.

A piece of foam damaged Columbia during its launch, causing the orbiter to break apart over Texas on Feb. 1, 2003, while en route to a Florida landing at the end of its mission. Seven astronauts were killed.

Since taking over as NASA’s top administrator, Griffin has welcomed criticism while maintaining that the decision-making power rests squarely with him and his managers.

“We do not shrink in NASA from criticism of our engineering processes, our decisions or anything else,” Griffin said, referring to the comments in Wednesday’s report. “We will look into it, we’ll evaluate it, and we’ll make a decision, move on, and our superiors and our stakeholders will judge us for what we have done.”

Discovery’s launch last month was the first since the Columbia tragedy, and the ship landed safely in California last week after bad weather kept it from returning to Kennedy Space Center.

The shuttle is expected to begin its cross-country jaunt back home Friday atop a modified 747 jet. The plane will need to stop for fuel, and possibly to avoid any weather problems along the way. But the shuttle could be back in Florida as early as Saturday afternoon.

Now that NASA is targeting a March launch, Gerstenmaier said it would use Discovery for the next mission instead of shuttle Atlantis as previously planned. This avoids the need to launch Atlantis on back-to-back flights next year. The ship is the only one suited to carry a large piece of the space station – a truss – to the outpost on the mission after next.

Even with delays and recurring problems, Griffin said, NASA still expects to complete construction of the space station by the time the shuttle fleet is retired in 2010. President Bush set that retirement date earlier this year as part of his plan for NASA to develop a new vehicle that could go to the moon and even Mars someday.

Discovery, which spent nine days at the international space station, left the outpost well-stocked and in good condition. Griffin said NASA would continue to pause between missions to address concerns.

“We will, after every flight, face up to whatever facts, whatever cards nature is dealing us,” Griffin said. “But our plan is to use the shuttle fleet to essentially complete assembly of the space station in the years that we have remaining.”

(c) 2005, The Orlando Sentinel (Fla.).

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Distributed by Knight Ridder/Tribune Information Services.

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