GRAHAM WARWICK / WASHINGTON DC
Shuttle probe cites foam and "broken safety culture" and urges recertification if vehicle is to operate after 2010
There were two causes of the Space Shuttle Columbia accident, investigators conclude in their final report. The physical cause was a breach of the orbiter's thermal protection system by insulating foam shed from the external tank after lift-off. The organisational cause was "the loss within NASA of its system of checks and balances", says Columbia Accident Investigation Board (CAIB) chairman Hal Gehman.
The report makes 29 recommendations that tackle both causes, 15 of which must be implemented before the Shuttle can return to flight, the CAIB says. The remainder are longer-term "continuing to fly" recommendations made because, based on NASA's history, the board "has no confidence that the Space Shuttle can be safely operated for more than a few years based solely on renewed post-accident vigilance".
Investigators found a "broken safety culture...with echoes of the Challenger accident" in NASA's human spaceflight organisation, with safety losing out to cost and schedule. The board recommends NASA establish an independent engineering authority responsible for all technical requirements and waivers.
"The programme should not be deciding its own margins," says board member Stephen Turcotte. NASA must also implement an independent safety programme and reorganise the programme office to improve integration of all the Shuttle elements.
NASA's Shuttle budget and workforce was cut by 40% in the 1990s, the report notes. "This left too little margin for robust operations. They were operating too close to too many margins," says board member John Logsdon. A "mischaracterisation" of the Shuttle as a mature system led NASA to hand operations over to a contractor and back off its safety oversight. "That was a mistake," he says.
The report criticises NASA for downsizing its quality assurance programme and failing to adapt inspection procedures to the increasing age of the orbiters. "As aircraft age, inspection points change. This is lacking in the Shuttle programme," says Turcotte. NASA has also failed to keep pace with advances in inspection technology. "They have 20-year-old inspection equipment that is frozen in time," he says.
While the CAIB concludes the Shuttle "is not inherently unsafe", it recommends the vehicle be recertificated in 2010 if it is to be operated to 2020 or beyond. "If the intention is to fly past 2010, then the Shuttle needs to go through recertification. It may not pass, or it may be too expensive," says Gehman. The Shuttle should be replaced as soon as possible, the board says. "We believe another vehicle as a complement or a replacement is a high priority," he says.
The final part of the report looks at the implications of the Columbia accident for the future of human spaceflight. "The report should now be the basis of a vigorous public policy debate on what to do next," says Gehman. "How soon do we replace the Space Shuttle, what is the US vision for human spaceflight and are we willing to resource that vision? This stuff is not cheap," he says.
Not all CAIB members, however, appear satisfied with the report. Brig Duane Deal is concerned that NASA will not make all the required changes before return to flight and says that tougher recommendations were buried or dropped from the report. Of concern are corroded parts, brittle bolts, launch pad systems, and weakened full-circumference rings attaching the fuel tank to the solid rocket boosters.
Source: Flight International
