The U.S. space shuttle Discovery is preparing for lift-off Wednesday night on a mission to boost the power supply of the International Space Station. If the launch goes as planned, the shuttle will arrive at the International Space Station on Friday. Moreover the wheather is favorable for the launch from Kennedy Space Center in the southeastern U.S. state of Florida.

"We're not tracking any issues, so the team is anxious to go," Launch Director Mike Leinbach said at a pre-flight briefing. The launch was delayed by a month while teams of engineers worked through concerns over hydrogen valves in the engine compartment. Problems with one of the three valves on the last shuttle flight raised the launch team's anxiety level.

Packed aboard the spacecraft is a new set of solar panels to be installed on the station, as well as the final stretch of the ISS's massive backbone-like girder and a new component for the urine recycler, a roughly 180-pound "distillation assembly."

Japanese astronaut Koichi Wakata will be on STS-119's seven-member shuttle crew. He'll be spending the next couple of months on the space station, replacing American astronaut Sandra Magnus, who returns to Earth when Discovery comes home.

Seven astronauts altogether will ride Discovery into orbit, taking with them 31 thousands of framework which holds two folded-up solar wings and a radiator. The space station already has six electricity-producing wings; the two going up will be the last ones and elevate the orbiting outpost to full power.

This $300 million segment, in fact, is the last major American-made piece of the space station to be launched. Once the astronauts install the framework and the 115-foot-long wings are unfurled, the space station will be more than 80 percent complete.