Space program pioneers told Columbia investigators Wednesday that shuttle wings were never designed to be struck by anything and suggested NASA should have taken the potentially catastrophic problem much more seriously.

NASA's quick dismissal of wing damage from a chunk of foam insulation also was criticized during the daylong public hearing by a sociologist who spent nearly a decade studying and writing about the Challenger disaster.

The space agency never fixed the underlying institutional problems that led to the 1986 tragedy and many of them were repeated during Columbia's doomed flight three months ago, Boston College's Diane Vaughan said.

"Neither one of these accidents that we've had on shuttle require Ph.Ds in physics to understand," said Robert Thompson, who headed the shuttle program during the 1970s and helped design the spacecraft.

"Erosion rates on an O-ring, when there should be no erosion, is an obvious thing," he said, referring to the Challenger accident.

Thompson then turned to Columbia, which investigators believe was likely damaged by a piece of insulating foam that came off the fuel tank during liftoff.

"Kinetic energy of a 2 or 3-pound hunk of foam when it's traveling 700 feet per second, that's high school physics," he said. "It appears to me that the agency needs to, number one, make damn sure of the procedures" that bring reports of problems and corrective actions to the right people.

Thompson was among five retired NASA and contractor managers with expertise going all the way back to the Mercury, Gemini and Apollo programs who testified Wednesday morning before the Columbia Accident Investigation Board.

Vaughan, author of "The Challenger Launch Decision," told the board during the afternoon session that the similarities between the two accidents are alarming and that, in both cases, engineers' intuitions, hunches and concerns were disregarded by top management because of the absence of hard data.

"NASA as an organization did not learn from its previous mistakes and it did not properly address all the factors" identified by the presidential commission that looked into the Challenger disaster, Vaughan said.

As the public hearing drew to a close, investigation board member Steven Wallace observed: "NASA's taken quite a pounding here today."

The retired space officials agreed the reinforced carbon-composite panels that line the leading edge of the shuttle wings were a technical challenge back in the 1970s and were never meant to withstand a blow of any sort. Everyone was well aware of the vulnerability of the panels, Thompson said, noting: "We didn't do a dead chicken test on it. We knew damn well you could knock it off if you hit it with enough potential energy."

"The whole intent was to not let it happen," he said.

Thompson said he would not know how to design the shuttle wing to take a big strike, like Columbia's left wing did 81 seconds after liftoff Jan. 16.

Milton Silveira, who also helped to design the shuttle, said not even the wings of airplanes are designed to sustain such impacts. Thompson agreed, noting that NASA would have had to abandon the shuttle project in order to provide an impenetrable wing edge.

The investigation board has yet to settle on a cause, but say the evidence is pointing to a deadly breach along the leading edge of the left wing, most likely a missing seal. Under this scenario, the seal was struck by foam during liftoff and was jarred loose the next day in orbit. Two weeks later, on Feb. 1, the gap was expanded by the searing gases of atmospheric re-entry and led to the ship's destruction over Texas.

Thompson told reporters he was surprised that engineers concluded while Columbia was still in orbit that the piece of foam did not cause any severe damage and that the shuttle and its crew of seven would be safe coming home. He said if it were up to him, he would have fixed the longtime problem of foam coming off the external fuel tank well before Columbia's flight.

So why didn't NASA do that?

"You're asking me to crystal ball something," Thompson said. "I would venture this thought: You get used to a little bit of something happening," like foam shedding off the tank.

Even though Vaughan's book on Challenger generated quite a bit of publicity when it came out in 1996, and though she heard from numerous organizations interested in reducing risks and errors such as hospital physicians, submarine safety groups, nuclear regulatory operations and the Forest Service, NASA never contacted her.

"Everybody called. My high school boyfriend called," she said, generating a big laugh. "But NASA never called."

As the hearing was in progress, shuttle program manager, Ron Dittemore, announced he will leave NASA as soon as the investigation is completed. He said he had planned long before the accident to resign this spring, but stayed on to help in the aftermath.