Endeavour Fuel Cells, Main Engines Are Go

Shuttle Endeavour's power-producting fuel cell system is loaded up and ready for flight and checkouts of its three main engines are complete as NASA counts down to the planned launch Friday of the orbiter on its 25th and final flight.

Six astronauts will depart crew quarters in the Kennedy Space Center Industrial Area just before noon Friday, and a half-hour later, they'll begin boarding Endeavour at launch pad 39A.

Liftoff of Endeavour on NASA's 134th and penultimate shuttle mission remains scheduled for 3:47 p.m., midway through a 10-minute window to put the spaceship on course for a rendezvous and docking with the International Space Station on Sunday.

The weather is expected to be acceptable for launch, but the odds have dropped slightly, from an 80 percent to 70 percent, according to the latest forecast.

Engineers on Wednesday loaded the shuttle fuel cell tanks with liquid hydrogen and liquid oxygen. The two chemical reactants are combined to generate electricity to operate all spaceship systems. Potable water is a byproduct. The loading operation took about six to seven hours to complete.

Early today, the shuttle's three main engines were put through regular preflight checks, and later today, Endeavour's communications systems will be activated.

Coming up tonight: the Rotating Service Structure is to be backed away from Endeavour at 7 p.m. in preparation for external tank propellant-loading operations early Friday. A storm front is expected to sweep through the area late this afternoon and early this evening, potentially delaying the move. The rollback of the gantry can be delayed about 4.5 hours before impacting other preparations for Friday's planned launch.

Also of note: A brush fire about three miles from the launch pad Wednesday is now fully contained, but there still is smoldering and smoking. Helicopter water bucket operations will continue today as required.