The huge solar wings on the International Space Station (ISS) were successfully unfurled Friday, paving the way for the orbiting laboratory to power up to its full capacity for the first time.

NASA said "no difficulties were encountered" in deploying the wings after astronauts Steve Swanson and Richard Arnold Thursday bolted an S6 truss to the space station to hold panels forming the fourth and last solar antenna.

The payload is one of the last major tasks of the more than decade-long effort by 16 countries to build the 100-billion-dollar outpost in space.

Once activated, the solar array will have the capacity to generate some 120 kilowatts of usable electricity, enough to power about 42 large homes. The ISS had been producing 90 kilowatts before the addition.

The 14-tonne S6 truss was carried into space by Discovery, which blasted off Sunday from Florida with a crew of seven astronauts, and the orbiter's robotic arm was used to lift it out of the shuttle's bay.

Each solar array set has two wings measuring 115 feet (35 meters) wide by 38 feet (11.58 meters), for a total span of 240 feet (73 meters) when deployed, including the truss connecting the two panels and allowing them to pivot as they follow the sun.

The four panels -- two per wing -- contain 32,800 cells that convert sunlight into electricity.

Once deployed, the panels will boost the outpost's full power generation from 90 to 120 kilowatts, providing the power the space station needs to carry out scientific experiments planned by the European Columbus laboratory and the Japanese Kibo laboratory.

The space station will also be able to double the size of its crew from three to six, beginning in May.

During their spacewalk that lasted six hours and seven minutes, Swanson and Arnold also plugged in power and data connectors and prepared the panels, which had been collapsed like an accordion in a container aboard Discovery.

The next space walk is planned for Saturday at 1643 GMT by Swanson and fellow astronaut Joseph Acaba, and is set to last six hours and 30 minutes.

The two are due to remove two batteries from a part of the space station that will then be replaced during the next shuttle mission in June.

A third spacewalk has been planned for later in the mission.

In all, NASA has scheduled nine shuttle flights through 2010 to complete the construction of the space station.

Upcoming shuttle flights also include the last mission to service the orbiting Hubble telescope in May.

Discovery is due to land back on Earth on March 28 at 1742 GMT, two days after a Russian Soyuz mission takes off for the ISS carrying a crew of three, including US billionaire businessman Charles Simonyi, who has shelled out 35 million dollars for his second trip as a space tourist.

The Discovery mission, delayed five times, is the first by a US space shuttle in 2009.

It has been a near picture-perfect mission so far, barring the delayed lift-off and some pesky space rubble that had US and Russian experts braced to move the ISS in an "avoidance maneuver."