The space with the space station on Tuesday afternoon. The shuttle's seven-astronaut crew is delivering the S6 truss, which is the backbone piece, along with a nearly 5,000-pound, 230-foot set of solar arrays. The arrays are attached to the truss and may begin generating power for the space station as soon as Friday.

A robotic arm onboard the space shuttle, , and a robotic arm onboard the space station, dubbed, in turn, Canadarm 2, were used Wednesday to unload the truss from the space shuttle's cargo bay, according to Mike Curie, a spokesman for NASA.

Thursday, astronauts Steve Swanson and Richard Arnold set out on a six-and-a-half-hour space walk to install the truss. Curie said that the robotic arm on the space station maneuvered the truss into place while the space walkers watched to make sure it was aligned exactly. Then the astronauts screwed in the bolts while Canadarm 2 held the truss in place. The power and data cables have been attached to the truss and are expected to be powered up later Thursday.

On Friday, the solar arrays are slated to be unfurled and set up. They are designed to gather energy through 32,800 solar cells and then transfer that power through the truss to the space station's batteries.

Curie said they simply couldn't do the work without the use of robotics.