In a spacewalk Thursday, astronauts Steve Swanson and Richard Arnold worked with a robotic arm, , to get the S6 truss that will hold the arrays maneuvered into place and bolted onto the space station. From inside the Discovery Friday, the astronauts sent instructions to the truss to unfurl the attached solar arrays, which are 230 feet long when spread open and weigh nearly 5,000 pounds.

The solar arrays are designed to gather energy through 32,800 solar cells and then transfer that power through the truss to the space station's batteries. Unfurled and with data and power cables attached and tested, the arrays are expected to begin delivering energy to the space station sometime Friday, according to Debbie Nguyen, a spokeswoman for NASA.

Nguyen said there was a holdup with the unfurling process when one of the 30 solar panels stuck to another panel. The astronauts, however, waited about 30 minutes while the heat of the sun warmed the arrays and pulled them apart.

With the truss and solar arrays in place, the space station now is 81% complete, according to Nguyen.

She added that the solar arrays will produce enough energy to power 42 2,800-square-feet homes. That will double the amount of power that goes to science experiments onboard the station.