Washington: In a stern rebuke to NASA managers, Columbia investigation chief Retd Admiral Harold W Gehman said their "cavalier" attitude to safety sent the shuttle to its doom, killing seven astronauts including India-born Kalpana Chawla.

NASA cannot consider Columbia's February disintegration an example of "bad luck" because it "ignored" numerous problems within the shuttle programme that contributed to the break-up, Gehman told reporters.

"The Board is convinced that coming and going into space is a dangerous task. It is not like taking a drive in your car," he said.