Space Expert Faults NASA Over Foam Debris Hitting Columbia
NASA almost certainly violated its own flight safety margins when it repeatedly launched shuttles knowing that they could be hit by foam debris from the external fuel tank, a retired Air Force space expert told Columbia accident investigators.
Since the orbiter was destroyed Feb. 1, the possibility that falling foam damaged Columbia’s thermal protection tiles has played a key role in the investigation.
NASA long had known that insulation from the tanks had gouged the delicate heat-shielding tiles in previous flights; however, officials had decided the gouging wasn’t a safety hazard.
“There is no way you can say you are operating within [safety] margins if you have foam of unknown size impacting the flight surfaces,” said Aloysius G. Casey, a retired general who once ran the Air Force’s centers for developing ballistic missiles and spacecraft. He spoke at a public hearing held here by the Columbia Accident Investigation Board.
Although NASA has conducted tests through the years to assess the damage that foam debris might cause, the original design of the shuttle never anticipated that risk, Casey said. It is believed that a 2.6-pound piece of foam hit Columbia’s left wing.
Casey said it is unclear what changes would be needed to keep foam from falling off the external tank. He suggested that reducing the thickness of the insulation could help keep it bonded to the tank during liftoff.
But Casey also warned the board against trying to make comprehensive safety improvements.
“It is impossible in ... a system as large and complex as the shuttle to identify with any certainty the next most-probable [cause of] failure,” Casey said. NASA could very well spend a lot of money, he said, on things that are not likely to cause the next problem.
The shuttle has a 98.4% probability of flying a successful mission, given that it has failed twice in 113 flights, he said. While that is better than unmanned rocket launchers, it is not good enough for human spaceflight, Casey said.
Such a rate in commercial air travel would translate to 640 crashes every day, said Steven B. Wallace, a board member and civil aviation accident expert.
The hearing included testimony from Kennedy Space Center director Roy Bridges and shuttle processing chief Bill Higgins -- both of whom discussed the complex organization that gets the space shuttle ready for flight and attempts to ensure safety.
Bridges said that in 1999, he had to issue urgent warnings within NASA that Kennedy was losing critical skills because of budgetary cutbacks.
The space center had 2,498 employees assigned to the shuttle in 1992. But by 1999 that number had fallen to 1,687. It is currently 1,773.
Bridges said he had no direct role in assessing the risks facing Columbia during its flights and had not known earlier that foam debris posed a serious safety problem.
He said many of Kennedy’s physical facilities are dilapidated and that NASA is facing massive investments if it wants to continue operating the shuttle for 10 to 20 more years as it has indicated.
Just new doors, siding and a roof for the vehicle assembly building, where the shuttle is attached to its solid rocket boosters and its external tank, would cost $100 million, he said.
Higgins described the system NASA uses to oversee the private contractor that processes the shuttle for launch. There are now 8,500 items that must be checked before launch.
Separately Tuesday, the independent Aerospace Safety Advisory Panel issued a report that said the shuttle fleet is encountering increasing problems as it ages and that NASA needs to reconsider how it certifies the vehicles as safe to launch.
The panel’s report was written before the Columbia accident but it had not been publicly issued.
The 106-page report said cracks, leaks and other problems were evidence of “degradation” and that the space agency should reevaluate the certification it has on various systems. The report did not mention foam debris problems.
Columbia was the oldest orbiter in the fleet, having first flown in 1981. The investigating board also is looking into how age may have diminished safety margins over the years.