NASA loading Atlantis fuel cells

Shuttle Atlantis' power-producing fuel cell system is being prepped for flight today as countdown to the planned launch Wednesday of an International Space Station assembly mission continue at Kennedy Space Center.

Engineers are loading liquid oxygen and liquid hydrogen into the system, which uses the commodities as chemical reactants to generate electricity to power spaceship systems and drinking water as a byproduct.

The weather outlook for launch remains good. Meteorologists say there is an 80 percent chance that conditions will be acceptable for launch. The chance of thick clouds or rain within 23 miles of the shuttle runway at the coastal spaceport are the only concerns. Those conditions could hamper a commander's ability to return safely to the runway if an emergency landing became necessary.

See the detailed forecast here: STS115WXL2.pdf

Liftoff remains scheduled for 12:29 p.m. Wednesday.