Washington - Nasa's quick decision to ground the space shuttle fleet while engineers search for the cause of tiny cracks in the rocket engine fuel lines was applauded by experts who said it shows the agency is putting safety above schedule.
Even though grounding the fleet cripples the National Aeronautics and Space Administration's efforts to keep its tight schedule for building and supplying the international space station, officials said there was no hesitation in taking the action, even though it is not clear the cracks represent a risk.
"These days, the value of safety is higher in the Nasa culture than it has ever been," frequent space agency critic Keith Cowing said on Tuesday.
Cowing, the editor of Nasa Watch, a watchdog website, said that earlier in Nasa's history, "You didn't want to be the guy who stood up and said, We shouldn't fly. There's been a slow-motion change in that culture and that's good."
Nasa engineers said they aren't even sure the problem is a threat to safety. They found minuscule cracks in the metal liner of fuel lines that carry super cold hydrogen to the main rocket engines.
The cause of the cracks and the extent of the threat they represent are unanswered questions, said Nasa spokesperson James Hartsfield, but that alone is enough now to ground the fleet.
"When there is something that we don't understand, it is a safety concern for that reason," Hartsfield said. "We need to get answers."
James Oberg, a veteran space engineer, author and Nasa watchdog, applauded the decision to ground the shuttles. Ignoring such a cautious, careful approach, he said, contributed to the 1986 explosion of space shuttle Challenger that killed seven astronauts, and to the loss in 1999 of three unmanned spacecraft sent to Mars, he said.
"This is the safety attitude from Apollo that some programme managers forgot prior to Challenger," Oberg said. Apollo was the Nasa programme that landed American astronauts on the moon.
Grounding the fleet to find the answers "is a refreshing reminder that there is a backbone of integrity within mission operations that is critical to success in space", Oberg said.
Hartsfield said Nasa engineers are just beginning to search for solutions to the fuel-line cracks, and it could be weeks before the shuttle fleet is cleared to fly again.
That means possible delays for missions scheduled for July, August and October. The October flight is critical since it involves resupplying the international space station and rotating crew members from the orbiting laboratory.
The fuel-line problem - a single, tiny crack in the lining of one of 12 fuel lines - was discovered during a routine inspection of space shuttle Atlantis. Nasa engineers checked the fuel lines on space shuttle Discovery and found more cracks. That was enough to ground the fleet of four space shuttles. - Sapa-AP