Poor leadership also made shuttle Discovery's launch more complicated, expensive and prolonged than it needed to be, the seven members said.
In fact, some of the "disturbing" traits that contributed to the Columbia tragedy - such as smug, overbearing managers influencing key decisions - were still present in the months leading up to Discovery's launch in July, the panel said.
"We expected Nasa leadership would set high standards for post-Columbia work ... We were, overall disappointed," they wrote.
The critique by the seven was included in the final report of the full 26-member task force, which was released on Wednesday.
At a news conference yesterday, Nasa's administrator, Michael Griffin, said he knew part of the task force had serious concerns, and he urged members to "speak their minds" and include the criticism in the group's official report.
"When I was asked the question, 'Do you want to hear this stuff,' the only answer I could ever give would be, 'Yeah, I want to hear it,"' Mr Griffin said. "We do not shrink in Nasa from criticism of our engineering processes, our decisions or anything else. We will listen to it, we'll evaluate and we'll make a decision."
The seven critics were a former shuttle astronaut, a former undersecretary of the Navy, a former Congressional Budget Office director, a former moon rocket engineer, a retired nuclear engineer and two university professors.
The group concluded in late June in an advance summary - just a month before Discovery's liftoff - that the space agency failed to satisfy three of 15 return-to-flight recommendations.
Those three failed recommendations were arguably the most critical: 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.Reuse content