NASA officials have postponed the planned launch of the space shuttle Atlantis until no earlier than Saturday over worries about fuel sensor readings.
They said they believed a wiring problem caused two of four fuel tank sensors to fail and were trying to determine if it would be possible to either fix the problem or launch the mission safely anyway. The shuttle was originally scheduled to lift off on Thursday.
NASA has until 13 December to launch the 11-day mission this year and take the European Space Agency's Columbus science laboratory to the International Space Station.
The weather was fine and everything had seemed ready for the third on-time launch this year. But on Thursday morning two of the four engine cut-off sensors – or ECOs – inside the liquid hydrogen section of the tank failed a routine pre-launch check.
"We have these sensors at the bottom of the tank, kind of like the fuel tank in your vehicle, and they tell us when we are about to run out of fuel," said LeRoy Cain, head of the shuttle Mission Management Team.
The shuttle uses more than 500,000 gallons (2.2 million litres) of liquid hydrogen and oxygen to get into orbit. If the engines keep firing after the tank is empty, it could spark an explosion.
Engineers and other experts have been meeting to discuss the problem and were ordered to go home and sleep on it. "I can almost guarantee you we will have some new thinking, too, after we let this team go home and rest," Cain said.
The first mission after the 2003 loss of the shuttle Columbia and its seven astronauts, in July 2005, was delayed by 13 days due to sensor glitches.
The Space Shuttle - Learn more in our continuously updated special report.
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