Shuttle reliability debated
March 26, 2003
CAPE CANAVERAL -- NASA may have to live with a risk factor of two catastrophes for every 113 shuttle flights, so it should limit its crew size and use robots and unmanned rockets whenever possible, a missile and rocket expert said Tuesday.
Aloysius Casey, a retired Air Force lieutenant general, also recommended to the Columbia Accident Investigation Board that space shuttle flights resume as soon as possible. The work force, skills and morale could erode to dangerous levels if the fleet is grounded for a long time, he said.
Casey put the shuttle's reliability at just over 98 percent, far better than for unmanned rockets, "but, in fact, I don't think it's good enough for optional human flight operations."
Casey, a consultant who was commander of the space division of the Air Force Systems Command, spoke in the third round of hearings before the board looking into the cause of the Feb. 1 shuttle disaster.
Investigation board member John Logsdon, director of George Washington University's Space Policy Institute, said he is not sure that 98 percent is a reliable number. "I'm not either," Casey replied.
High reliability is achieved through redundant shuttle systems and adequate margin, Casey told the seven board members who traveled from Houston for the first and only hearings in Cape Canaveral, home to Kennedy Space Center.
He said significant redesign of the shuttle could be a waste of money that wouldn't address "the next most probable failure cause."
Steven Wallace, a board member in charge of accident investigations for the Federal Aviation Administration, suggested that a reliability level of 98 percent would not suffice for commercial airlines.
"In 2000, we operated 11-million flights, 32,000 a day and without a single fatality," Wallace said. "Operating on this level of reliability, we would lose 640 of those airplanes every day."
At least three pieces of debris broke off Columbia's fuel tank barely a minute after liftoff Jan. 16 and hit the left wing. The board suspects a breach in the wing let in searing gases during the shuttle's return to Earth, causing the spacecraft to break apart.
The chairman of the investigation board, Harold Gehman Jr., agreed that the fuel tanks were not designed to shed debris during liftoff.
"They tried several fixes, and the fixes don't work," said Gehman, a retired Navy admiral.
Gehman stressed that the board has not yet concluded that the foam debris led to Columbia's destruction, "but it's an anomaly."
The investigation board also heard from Roy Bridges, the director of the Kennedy Space Center, and William Higgins, the chief of shuttle processing safety and mission assurance at Kennedy.
Bridges, a former shuttle pilot, said budget cutbacks resulted in a slashing of the center's civil servant work force during the 1990s and acknowledged that "we do miss things from time to time."
He told the board he was unaware of any safety concerns about flyaway tank foam and, if he had been, would have raised his hand at the flight readiness review and halted the launch.
"This is certainly a surprise to all of us," Bridges said.
UNMANNED MISSIONS READY: Despite the tragic loss of the shuttle Columbia and its crew, NASA is pressing ahead with an ambitious schedule of unmanned scientific missions to space starting next month.
Almost two dozen spacecraft are being readied to investigate Earth's environment, the solar system and the far corners of the universe during the next 10 years. They will join a fleet of about 30 science satellites soaring through the heavens.
A pair of robot rovers is sitting at the Kennedy Space Center, waiting to be boosted toward Mars later this spring.
The space agency needs "not an either-or but a combination" of unmanned and manned flights, NASA administrator Sean O'Keefe told reporters.
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