Gehman: Columbia investigation 'a real puzzle'
HOUSTON, Texas (CNN) -- The Columbia Accident Investigation Board began the first public hearing into the shuttle tragedy Thursday in a 500-seat auditorium not far from the Johnson Space Center.
Retired Navy Adm. Hal Gehman, who leads the board, said Wednesday data information compiled from sensors onboard the shuttle show the aerodynamic control surfaces were fighting drag earlier than previously estimated, "which means that perhaps the orbiter was wounded earlier than we thought."
Gehman also said a study of the nearly 20,000 pieces of debris recovered so far -- including all six of the shuttle's wheels -- shows that more than one tile had to have been damaged to lead to the catastrophe.
"We're pretty sure that the loss of one tile could not have caused the amount of heat that we're seeing inside the [left] wing," Gehman said.
He said the investigation is "a real puzzle" and said investigators don't yet "have that golden nugget," although he expressed confidence the board would find the answer.
"It may be a piece of debris in the field. It may be a piece of analysis, it may be a piece of telemetry," he said. "In my opinion, not everything is on the table yet."
However, Gehman said, his worst nightmare is that investigators would find out exactly what part of the shuttle failed, but not why it failed.
Regarding the board itself, Gehman said three new members have been added. They are Dr. Sally Ride, the first American woman to fly in space; Douglas Osheroff, a Nobel laureate who chairs the Physics Department at Stanford University; and Dr. John Logsdon of George Washington University's Space Policy Institute.
Ride, who has been in space twice, also sat on the Rogers Commission, the presidential board that investigated the 1986 Challenger disaster.
Some other changes in the board's makeup have come following criticism about conflict of interest, since some of the people involved in the investigation are top-level managers in the shuttle program at NASA.
An engineer whose team found errors in the safety of the space shuttle program was one of four witnesses expected to testify at Thursday's hearing.
Shuttle program manager Ron Dittemore also has been called as a witness as has Keith Chong, an engineer for Boeing, and Jefferson Davis Howell Jr., director of the Johnson Space Center.
He said there's not an adversarial relationship between the board and NASA, because "they want to get to the bottom of this as fast as we do," but he said it could get "a little more sporty as we begin to look at NASA's management issues, NASA's characterization of risk."
Part of the risk assessment refers to e-mails NASA released showing conversations between engineers about possible re-entry scenarios, taking into account possible damage to the left wing. Some of those missives predicted disastrous results, but in the end it was determined that there was no serious risk to the shuttle.
CNN Space Correspondent Miles O'Brien contributed to this report.