Endeavour cleared after heat shield inspection

KENNEDY SPACE CENTER, Fla. - After a close-up, focused inspection of a damaged heat shield tile on the belly of space shuttle Endeavour, NASA analysts have concluded that there is no threat posed to the orbiter, and NASA's Mission Management Team cleared the ship for re-entry as-is.

"So all good results all the way around," said MMT Chairman LeRoy Cain. "We're essentially clearing the vehicle for re-entry at this point. There were no dissenting opinions, no alternate opinions; the entire team was pretty much on board with the assessments that were done."

NASA managers were optimistic that would be the case, based on an analysis of long-range telephoto views shot during Endeavour's final approach to the station Wednesday, but today's focused inspection - utilizing an instrumented boom on the ship's robot arm - was ordered Friday to make absolutely sure.

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The inspection work began after midnight when the space station's robot arm was used to pull Endeavour's heat shield inspection boom, or OBSS, out of the ship's cargo bay for hand-off to the shuttle's 50-foot-long arm. Pilot Gregory Johnson, overseeing a series of computerized maneuvers, then positioned the arm under the shuttle's right side for close-up photos and laser scans.

The imagery and laser scans showed the damage site measured 2.43 inches by 2.95 inches with a maximum depth of .89 inches. Cain said the analysis showed the aluminum structure below the damage site would experience maximum temperatures of around 219 degrees Fahrenheit during re-entry, well below the 350-degree safety limit.

"With this data, to include the laser data that the team was able to acquire from the focused inspection, the analyses teams went back and essentially what they did is verify how much tile is still in the cavity," Cain said. "Because, of course, it's more important what remains than it is what's gone, per se. What we're interested in is protecting the structure underneath the tile and the associated systems."

And based on that analysis, "it was clearly OK," he said.

To make doubly sure they were on solid ground, analysts created a three-dimensional representation of the damage that had the uniform shape required for computer modeling. As such, the computer model assumed more damage than was seen in the actual gouge, "and in running that analysis, they determined we still cleared with plenty of margin."

The astronauts went to bed not knowing the Damage Assessment Team results, but Cain said they knew engineers were optimistic.

With the damage site cleared for entry as-is, the astronauts will have one less worry as they prepare for a second spacewalk Sunday to add ammonia coolant to a space station solar array.