Space shuttle Atlantis cleared for launch Friday

CAPE CANAVERAL, Fla, Sep 8 (Reuters) NASA will try to launch the space shuttle Atlantis today after clearing a technical problem with a power generator that forced a two-day delay, officials said on Thursday.

The US space agency had planned to launch Atlantis on Wednesday on the first construction mission to the International Space Station since the 2003 Columbia disaster, but a problem in a motor inside one of the shuttle's onboard fuel cells prompted managers to delay the launch.

The flight was previously postponed by a lightning strike and a storm.

''The team came to the conclusion today that the cloud we saw over fuel cell number 1 was probably acceptable to fly with,'' shuttle program manager Wayne Hale said following a meeting of top NASA officials.

Launch time today is 11:41 am (2111 hrs IST). NASA forecasters predicted a 70 per cent chance of acceptable weather for liftoff.

If Atlantis does not fly today, NASA had agreed to delay the mission so that Russia could proceed with its launch of a Soyuz spacecraft that will ferry a new crew to the space station, along with an Iranian-born American entrepreneur, Anousheh Ansari.

But NASA managers said they were talking with Russian space officials to allow Atlantis to be launched tomorrow if today's attempt has to be called off. That could leave as few as two days between the shuttle's departure and the arrival of the Soyuz.

The power problem, a voltage spike in one of the three fuel cells on the shuttle, was found shortly before the shuttle was to be loaded with a half-million gallons of propellants for launch on Wednesday.

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.

Hale said there was ''some risk'' in flying with the troublesome fuel cell, but not to the spacecraft or crew. Rather a failure of the fuel cell during the flight could cut the mission short.

NASA's top safety officer, along with the fuel cell manufacturer, urged managers to delay the flight and replace the fuel cell. But Hale and other managers said they believed it was riskier to try to replace the device, located beneath the payload bay floor.

Atlantis' crew is to deliver and install a 372 million dollars solar power module to the space station. Even with a fuel cell failure, NASA wants to at least unload and attach the module, leaving its checkout and deployment for the space station crew or a future shuttle mission.

If NASA misses this week's launch window, the next opportunity for Atlantis to fly would be on October. 26 under current requirements for daytime launches.

NASA is looking into lifting its self-imposed ban on night flights, which was enacted after the Columbia accident so cameras could have a clear view of liftoff.

Foam fell off Columbia's fuel tank during launch, striking the ship's wing and damaging its heat shield. The shuttle broke apart as if returned to the atmosphere for landing, killing all seven astronauts aboard.

Construction of the 100 billion dollars space station has been on hold since the accident.

NASA has just four years to finish building the orbital complex before the space shuttles are retired. The station's structural trusses, modules and other major components were designed to be launched only on the shuttles.

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