Another technical problem forced officials with the U.S. space agency NASA to delay Friday's planned launch of the space shuttle Atlantis. VOA's Richard Green has more on the latest postponement of a critical mission to the International Space Station.
NASA engineers discovered a problem with a fuel sensor on the large external tank of the space shuttle Atlantis, hours before Friday's scheduled liftoff.
As the shuttle crew and technicians went through the normal last-minute preparations, NASA officials met to decide whether to proceed with the launch.
Finally, with just a few minutes remaining in the countdown, flight controllers announced their decision.
"Mission management team has decided that we are no-go for that mission today, so we would like you to execute a 24-hour scrub turnaround," they said.
The sensors are part of a complex system that measures the amount of hydrogen fuel in the external tank during launch. The system shuts down the shuttle's main engines before the tank runs out of fuel. If the engines shut down at the wrong time, they could either rupture, or shut down prematurely.
Bad weather and a problem with one of the shuttle's fuel cells have forced NASA to cancel three previous attempts to launch Atlantis since late August.
Wayne Hale, the manager of the space shuttle program, says he is taking every precaution to ensure the safety of the crew.
"Launching rockets is not like going down to the airport and hopping on a jetliner someplace," he said. "This is a much more complicated vehicle that has got to fly - I think we did the calculation one time - 30 times faster than your typical jet airliner; it certainly flies 100 times as a high. This is a lot more exotic regime. The stresses are higher, the margins [for error] are smaller. This is not an ordinary, everyday mode of travel we are talking about."
NASA rescheduled the launch for Saturday. Atlantis is to spend 11 days in space on a mission aimed at jump-starting construction on the International Space Station. The crew will attach a 17-ton segment of the orbital outpost that contains a new set of giant solar energy panels.
This mission has been delayed since the 2003 space shuttle Columbia disaster.
Officials say weather conditions are favorable for Saturday's planned launch.
If the launch is postponed again, NASA will have to wait until at least October before making another launch attempt.