NASA prepares for shuttle propellant load

NASA contractor technicians are preparing to load toxic rocket propellants aboard Discovery this week while engineers sort out an electrical problem with one of the shuttle's two solid rocket boosters.

The hypergolic propellants, which ignite on contact, will power Discovery's twin orbital maneuvering engines and 44 nose-and-tail steering jets during a test flight scheduled for launch on July 1.

The highly toxic propellants also are used to run the shuttle's three Auxiliary Power Units, which provide the hydraulic power needed to steer the ship's main engines during launch and operate its wing flaps, rudder speedbrake, landing gear and nosewheel steering system during atmospheric reentry and landing.

The oxidizer nitrogen tetroxide and the fuel monomethyl hydrazine will be loaded into tanks aboard Discovery on Thursday and Friday, respectively.

Engineers, meanwhile, are troubleshooting what appears to be a minor electrical problem on the shuttle's lefthand rocket booster. A glitch cropped up with a power distribution circuit that delivers electricity from the shuttle orbiter to the booster. The problem prompted a power shift to a back-up circuit.

"I don't think they consider this a major issue," said Kennedy Space Center spokeswoman Jessica Rye. "But they do want to take a look at it and see why it switched to the back-up circuit."

Discovery and a crew of seven astronauts are to be launched on NASA's second post-Columbia test flight, which also will serve as a supply run to the International Space Station. The launch window for the mission will extend through July 19.