A giant solar wing ripped as it was being unfurled by astronauts aboard the international space station, creating another problem for NASA at the orbiting outpost.
The next shuttle flight could be delayed if this latest problem is not resolved quickly, said NASA's space station program manager, Mike Suffredini. Atlantis is supposed to lift off in early December with a European laboratory.
"We don't clearly know what we're dealing with yet, and as soon as we know what we're dealing with, then we can talk about what our next steps are," Suffredini said.
The astronauts immediately halted the wing extension when they spotted the damage. By then, the solar panel was already extended 90 feet (27.4 meters) of its 115 feet (35 meters). Space station commander Peggy Whitson said the sun angle prevented her and the others from seeing the 2 1/2-foot (75-centimeter) tear sooner.
"It's just the way it goes," Mission Control said consolingly.
The torn solar wing can still provide power. NASA's bigger concern is the structural problem posed by a partially deployed panel.
The damage was especially agonizing for the 10 space travelers because it came on the heels of an otherwise hugely successful day. Two of shuttle Discovery's crew had just wrapped up a seven-hour spacewalk and were still reveling in the smooth extension of the first of two retracted solar wings on a newly installed beam.
During the spacewalk - the third of their mission - Scott Parazynski and Douglas Wheelock installed a massive beam holding a pair of solar wings, which were folded up like an accordion. It took three days to move the beam from one location on the space station to another 145 feet (44 meters) away and was considered one of the hardest construction jobs ever attempted in orbit.
Parazynski also dealt with the other problem on the space station, inspecting one of two rotary joints that keep the station's solar panels turned toward the sun.
Steel shavings were found during a spacewalk over the weekend in the joint on the right side of the station, and Parazynski was asked to look at the left joint for comparison. Everything inside that joint was shiny and looked pristine.
Until NASA figures out what is grinding inside the gears and fixes it, the right joint will remain in a parked position as much as possible, limiting power collection.
Astronauts awoke Wednesday to the sounds of "Nel Blu Dipinto di Blu" ("In the Blue Painted Blue"), more commonly known as "Volare."
"Thank you for giving us a song that we can sing all day," Shannon Lucid told Italian astronaut Paolo A. Nespoli.
NASA plans to take a closer look at the malfunctioning joint during a spacewalk on Thursday, although that work might be upstaged by the solar wing trouble.