A pair of spacewalking astronauts disconnected an old empty ammonia tank outside the International Space Station and got a new one ready to put in its place.
In the first of three spacewalks needed to complete the job, Clayton Anderson had no problem taking apart the ammonia lines on the old tank. But he needed a pry bar to remove the new tank out of space shuttle Discovery's payload bay. The tank got hung up on a bolt.
"Go nice and easy, Clay," spacewalking partner Rick Mastracchio warned as Anderson pushed and prodded with the pry bar. After several tries, the tank finally came free. "We got it!" Anderson called out.
The two men lifted the 770-kilogram tank out of Discovery and handed it off to a robot arm, which manoeuvred it to a temporary storage location at the space station.
The actual swap-out of the two tanks will take place during the second spacewalk Sunday, with the entire effort wrapping up on the third and final outing Tuesday. It will be "a big juggle" with the tanks, said David Coan, Mission Control's lead spacewalk officer.
Besides the tank work, Mastracchio and Anderson collected a science experiment from the space station's Japanese lab and replaced a failed station-positioning device.
Then the game plan changed. Instead of tackling battery work, they focused on hoses and clamps. Astronaut Dorothy Metcalf-Lindenburger, directing the spacewalk from inside, urged the men to go slow because of the switch.
Mastracchio and Anderson were originally scheduled to work on old batteries on the far left end of the space station, along the sprawling power truss. But based on new findings, NASA cancelled the task this week because of concern the two might get shocked. The job instead will be carried out on the next shuttle flight, once the spacesuits are better protected.