Nasa's latest shuttle efforts were tainted by some of the problems that caused the Columbia disaster, seven members of an oversight panel say.
Some of the same problems plagued this flight, panellists say
Their views are included in a report by the Return to Flight task group, overseeing how Nasa responds to recommendations following Columbia.
They said leadership shortfalls made the shuttle effort costlier, longer and more complex than it needed to be.
Space shuttle Discovery launched successfully from Florida on 26 July.
The task group's final report was released on Wednesday. The views of the more critical seven panellists are individual observations only.
Nasa's administrator Michael Griffin requested that all individual comments, including the 20-page critique from the seven panel members, be included in the official task force report.
It was the first flight since shuttle Columbia broke up over the US in 2003, killing seven astronauts.
"We expected that Nasa leadership would set high standards for post-Columbia work...we were, overall, disappointed," the panellists wrote in the report.
"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 seven critics included a former shuttle astronaut, former undersecretary of the Navy, a former congressional budget office director, former moon rocket engineer, a retired nuclear engineer and two university professors.
They were part of the 26-member Return to Flight task group appointed to evaluate how the US space agency meets the recommendations by the Columbia Accident Investigation Board (Caib).
The task group concluded in an advance summary in late June - just a month before Discovery's launch - that Nasa had failed to satisfy three of the 15 return to flight recommendations.
Those three failed recommendations were: an inability to prevent dangerous pieces of foam and ice from breaking off the fuel tank during launch; no capability to fix damage to the shuttle in orbit; and a failure to make the shuttle less vulnerable to debris strikes.
But during launch on 26 July, a 1lb (450g) chunk of foam debris peeled away from the external fuel tank, though, fortunately, the foam did not hit Discovery.
Nevertheless, Nasa has since grounded the entire shuttle fleet until the problem has been fixed.