Nasa compromised safety in an attempt to meet unrealistic launch dates for the space shuttle Discovery, according to a report by some members of a taskforce appointed by the space agency to monitor safety.
Poor leadership by smug managers who influenced important decisions - some of the same "disturbing" traits that contributed to the Columbia disaster - were still present in the run-up to Discovery's flight, the report said.
"We expected that Nasa's leadership would set high standards for post-Columbia work ... We were, overall disappointed," the report said.
"It is difficult to be objective based on hindsight, but it appears to us that lessons that should have been learned have not been."
The report was produced by seven of the 26 members of an oversight committee assigned to monitor Nasa's progress as it implemented the recommendations of the Columbia accident investigators.
The criticism by the seven, who included a former shuttle astronaut and a former rocket engineer, was appended to the taskforce's final report which was published yesterday.
The full oversight group concluded in late June, a month before Discovery's lift-off on the first shuttle mission since the Columbia disaster, that Nasa failed to satisfy three of the 15 return-to-flight recommendations.
They included an inability to prevent dangerous pieces of foam and ice from breaking off the fuel tank during launch; an inability to fix any damage to the shuttle in orbit; and a failure to make the shuttle less vulnerable to debris strikes by toughening the outer skin. A chunk of foam insulation broke off Discovery's modified fuel tank during liftoff on July 26 but did not strike the shuttle. A similar piece of foam struck Columbia during liftoff in 2003, rupturing the protective heat shield and causing the shuttle to burn on re-entry.
The minority group criticised Nasa for describing the fuel tank as "safer", the "safest ever" and"fixed" when there was no evidence to support these claims.
They also accused managers of adjusting "performance standards" when targets did not meet the launch schedule.
"When achievements are mandatory at first but become 'goals' when the going gets tough, it sends a strong message to everyone that nothing is mandatory," they concluded.
They said personalities had been allowed to dominate over process. "Roles, positions and strength of personality often determined critical outcomes more than facts and analysis."
But the group's co-chairman, Richard Covey, cautioned against reading too much into the appended report, telling the New York Times that other members of the panel were not disturbed by Nasa's approach to safety.
"I personally did not find the process as it played out unusual," he said, adding that Nasa "did a competent job."