Launch controllers will load oxygen and hydrogen into the fuel cells aboard space shuttle Endeavour this evening as the countdown to the launch of STS-126 moves ahead smoothly. The fuel cells convert the chemicals into electricity while Endeavour is in space.

The process also produces water for the crew. Endeavour Commander Chris Ferguson and Pilot Eric Boe will also fly several practice landings aboard NASA's Shuttle Training Aircraft overnight. STS-126 is to lift off Friday at 7:55 p.m. EST.

The Mission Ahead

The flight of space shuttle Endeavour includes several significant steps to install new crew equipment inside the International Space Station and service the solar array joints of the laboratory. During STS-126, the crew of space shuttle Endeavour and the space station will:

+ Exchange crew members. Sandra Magnus will swap places with current station resident Greg Chamitoff.

+ Conduct four spacewalks. Working in teams of two, astronauts will emerge from the space station's Quest airlock and work on the two large joints that turn the station's massive solar array "wings." They are to service the starboard side joint and perform preventative maintenance on the port side joint.

+ Install new crew quarters, a galley, waste water recycling system and oxygen generator inside the space station. The equipment has been packed inside refrigerator-sized racks that require forklifts to lift them on Earth. But in space, a single astronaut can move a rack around with little problem.

Endeavour and its crew are to land at NASA's Kennedy Space Center after 15 days in space.