Cape Canaveral, Fla. Space shuttle Endeavour's astronauts slowly but successfully unfurled the second of the international space station's giant solar wings Monday, completing the largest structure ever deployed in orbit.
NASA had delayed spreading the second wing by one day after the first wing appeared too slack.
Shuttle commander Brent Jett Jr., using computer commands, carefully unfolded the second wing a few feet at a time in a start-and-stop procedure that took almost two hours. A couple sections stuck together and had to be jarred loose by retracting the panel a little and then shooting it back out.
The glimmering blue and gold-colored wing began generating electricity even before it reached its full 115 feet. To NASA's relief, the panel stretched tight.
"Great work, gentlemen," Mission Control said. "You've got a lot of happy folks down here. We think you've earned your solar wings."
"There was a fair amount of tension in the cockpit," replied astronaut Joe Tanner.
Following Monday night's feat, the space station's new solar wings spanned 240 feet from tip to tip, including connecting beams.
The right wing was extended Sunday night via computer command to its entire length in just 13 minutes. But it snapped back and forth as it went out, and two tension cables apparently came off their pulleys, leaving the blanket of solar cells less taut than desired.
The problem did not appear to affect the wing's electricity-generating ability, said flight director Bill Reeves.
The main concern was whether the wing would be secure enough during the docking or undocking of a space shuttle, or during orbit-changing maneuvers. The worry is that vibrations could tear, bend or break off the solar panels.
The space agency said that it is possible no repairs or extra work will be needed and that the solar wing has an acceptable amount of tension.
The $600 million set of solar wings is the largest, most powerful and most expensive ever built for a spacecraft. The panels are based on a design originally intended for NASA's space station Freedom, a project proposed by President Reagan in 1984 that slowly and agonizingly evolved into what is currently orbiting Earth.
With a combined length of 240 feet and a width of 38 feet, space station Alpha's solar wings have half an acre on which to collect sunlight and transform it into electricity.
Alpha commander Bill Shepherd and his Russian crew need more power in order to spread out in the complex where they have been living for the past month. One of the space station's three rooms has been unheated and sealed to conserve power. A fourth room, the American-made Destiny lab module, due to soar in January, requires considerable electricity for experiments.