HOUSTON, July 31: Nasa administrator Michael Griffin said on Sunday that the US space agency had ‘goofed’ on vital safety checks before launching the shuttle Discovery and that it was ‘lucky’ the shuttle had not sustained serious damage during liftoff.

Facing down questions over a stray shard of foam which broke off from an external tank during Discovery’s launch on Tuesday, Griffin told NBC’s ‘Meet the Press’ that pre-launch checks had fallen short.

“Our judgement at the time was that it was okay,” the Nasa chief said of the structural reviews of the external tank and other vital equipment that was examined before Discovery’s liftoff.

“As everyone has said without any attempt to hide it ... we goofed on that one,” he said.

The shedding of foam debris during launch is alarming because it was just such a stray shard of foam that hit the space shuttle Columbia during liftoff.

The damage caused by the debris caused Columbia to disintegrate as it re-entered the Earth’s atmosphere in February 2003 killing all seven astronauts onboard.

Nasa grounded its shuttle fleet and implemented new safety procedures in the wake of the tragedy.

Griffin expressed confidence that Discovery would return safely to Earth, but conceded Nasa had been ‘lucky’ the craft was not seriously damaged during launch.—AFP