Cape Canavarel, Fla. ? NASA asked an astronaut aboard the international space station to exercise vigorously Friday, hoping the rapid movement would jostle a half-retracted solar wing that refuses to fold up properly.

German astronaut Thomas Reiter of the European Space Agency was told to do 30 seconds of robust exercise on a bungee-bar machine in an attempt to vibrate wires on the 115-foot solar array and prevent an unplanned, fourth spacewalk.

Reiter tried several times, but his exercise did not appear to change the solar array.

“I’m very sorry to hear that,” said Reiter, who has been at the space station since July. “I was training for it for a half year.”

Mission Control radioed back, “We’ll give you a silver medal for that.”

Earlier in the day, flight controllers jiggled the solar array 10 degrees to either side by remote control to try to relieve tension in a wire system that is preventing it from folding up like an accordion, as designed. That too did not appear to have the desired effect.

Flight controllers thought Reiter’s workout might fix the solar array problem based on previous experience. NASA officials recalled an incident in which the space agency saw an array shaking and found the cause was astronaut Leroy Chiao working the exercise device hard.

Space station crew members are required to exercise two hours a day to prevent loss of muscle mass.

In this image from NASA Television, European Space Agency astronauts Christer Fuglesang, left, of Sweden, and Thomas Reiter, of Germany, conclude a televised conversation Friday with Sweden's Crown Princess Victoria, Deputy Prime Minister Maud Olosson and a group of schoolchildren.

“If you think of the station as kind of a long beam … If you’re at one end putting a force into it, you’ll get some vibration going on,” Chiao told The Associated Press on Friday. He lived aboard the space station from October 2004 to April 2005.

The solar wing was part of an interim power system. A primary goal of space shuttle Discovery’s seven-day visit to the space station was to rewire the lab and hook a new set of solar wings onto the permanent electricity grid.

The new panels rotate with the movement of the sun to maximize the amount of solar energy produced, but in order for the new panels to spin, the old panel had to be retracted.

While it was folded far enough to give clearance to the new panels, the old one got stuck after retracting halfway. NASA had wanted it to retract fully.

NASA was considering a fourth spacewalk if Friday’s efforts failed, and the solar array could be jettisoned in a worst-case scenario.