Atlantis' astronauts Wednesday reeled in some of the cord towing a half-ton satellite above the shuttle to try to clear a jam in the 121/2-mile line but failed on their fourth try to fully deploy the craft.
Payload commander Jeffrey Hoffman this morning slowly spooled in nearly 90 feet of the 850 feet of tether connecting the Italian Space Agency's satellite to the shuttle.NASA managers hoped by backing up, then rolling out the tether faster than before, they could free the line from where they believed it was caught, as if on a balky fishing reel.
But when the astronauts tried to further release the satellite, the motor that pulls the tether off the spool and keeps it taut did not engage. A problem with the motor foiled the second failed attempt Tuesday to raise the satellite from its roost atop a 40-foot boom; it seemed to work fine on subsequent attempts that day.
The crew and Mission Control were working on the problem today, testing the motor and looking for any possible obstruction at the top of the tower.
The snag forced NASA to put on hold a risky experiment in which the astronauts are supposed to generate electricity by dragging the full length of the slender fiber-and-wire cord through Earth's magnetic field at 17,500 mph.
NASA added an eighth day to Atlantis' mission because of the problem and a delay in releasing another satellite over the weekend. The flight will end Saturday.
The astronauts were supposed to unreel the half-ton Italian satellite Tuesday on 121/2 miles of the cord, which is as thick as a shoelace.
But the cord unwound in fits and starts, and after three attempts, the astronauts had managed to reel out the satellite only 843 feet.
Mission Control said tension may have caused a snag on the reel. NASA mission operations director Randy Stone likened the problem to a fishing line caught among other coils on a reel.
Such a problem was not seen in training, said Sid Saucier, space systems project manager at NASA's Marshall Space Flight Center in Huntsville, Ala.
Twice during the attempt to unreel the spacecraft, the satellite swung over the shuttle on its cord.
But commander Loren Shriver fired the shuttle's jets to steady the tether and avert the possibility of an out-of-control satellite wrapping its cord around the spaceship. And Stone said the astronauts were never in danger.