NASA Weighed Redesigns for Shuttle's Foam

Lockheed Martin, which operates the Michoud Assembly Facility in New Orleans that applies the foam to the tank, declined to answer specific questions about the foam incident.

NASA officials indicated in news releases before the launch that they were still looking closely at redesigning the area where the problem occurred Tuesday. There are two similar foam wedges on the tank -- one near the top section that holds liquid oxygen, and the other on the bottom section, which holds hydrogen. The part that ripped off was near the hydrogen tank.

On the current flight, NASA continued its testing by placing devices to measure the wind speed or pressure, called accelerometers, on the tank.

The measurements were to "be used to determine whether there is need for the ramps in future tank modifications," according to a news release before the launch.

One focus for investigators looking into Tuesday's mishap will be a 10-foot section of the PAL wedge that had been dissected to make another repair that was also designed to reduce the possibility of losing foam, Malone said. The foam was then reapplied.

The foam-shedding problem had long plagued the space shuttle and proved to be one of the most vexing issues NASA faced after the Columbia disaster, several experts noted yesterday. NASA spent millions of dollars and thousands of hours implementing dozens of changes and safeguards that included improving the fitting that connects the external tank to the orbiter; a video camera on the liquid oxygen feed line to photograph liftoff; reversed bolts on the flange of the tank's midsection and a new process for spraying thermal foam on that area; redesign of the joints for movement along the liquid oxygen feed line to the main engines; and more rigorous procedure of spraying on the foam. The foam is needed to insulate the tank and keep the fuel at extreme subzero temperatures.

"They had a lot of different issues they were working after Columbia," said George Whitesides, executive director of the National Space Society. "Foam was one they threw quite a bit of resources at, and I think to a certain extent never got fully comfortable that they had solved it."

But several members of the Return to Flight Task Group, which helped oversee NASA's response to the Columbia disaster, said that although they were surprised and disappointed by the latest developments, the agency had taken a number of steps that seemed to have addressed the issue.

"I certainly believe from what I know that they had done whatever they could to fix the problem," said Kathryn Thornton of the University of Virginia. "You can think you have a problem fixed, but until you have a chance to test it you don't really know, and this was the test."

Nevertheless, the agency clearly had failed to solve the problem and now faces the daunting task of starting the process again, several experts said.

James N. Hallock, a member of the Columbia Accident Investigation Board and aviation safety manager of the Department of Transportation, said NASA needs to figure out how foam reacts to supersonic speeds.

"Do they really, really understand what's causing the problem?" Hallock said. "I suspect they really don't understand the mechanisms the way they really need to."

"Obviously they didn't do enough," said Jerry Grey, director of science and technology policy for the American Institute of Aeronautics and Astronautics. "What they have to do now is go back and review the whole process."