NASA postponed the launch of the space shuttle Atlantis on Wednesday because of a problem with a power system aboard the ship, officials with the US space agency said.
The launch of Atlantis on NASA's first construction mission to the International Space Station since the 2003 Columbia accident had been planned for 12:29 pm (1629 GMT) Wednesday. The next opportunity to fly would be at 12:03 pm (1603 GMT) on Thursday.
Engineers detected a voltage spike in a power unit inside one of the shuttle's three onboard fuel cells. The problem was found shortly before the shuttle was to be loaded with a half-million gallons of propellants for launch.
The 250-pound (113-kg) units combine oxygen and hydrogen to produce electricity for the shuttle's systems and water that is used for cooling and for the crew to drink. All three must be operating for the shuttle to fly.
Preliminary analysis points to a glitch in a Freon cooling loop that is part of the system, said NASA spokeswoman June Malone. NASA needs to resolve the problem quickly to take advantage of the two remaining days in the shuttle's launch window.
After Friday, NASA has agreed to delay the flight so that Russia can proceed with its launch of Soyuz spacecraft that will ferry a new crew to the outpost along with an Iranian-born American entrepreneur, Anousheh Ansari. She will fly home with the current station crew in a Soyuz capsule that is nearing the end of its orbital lifetime.