The latching mechanism on one end of the 58-foot robot arm malfunctioned in August. It needs to be replaced before an Orbital ATK supply ship launches in November.
Within an hour-and-a-half, the spacewalkers had unbolted the degraded mechanism from the arm and turned their attention to the replacement part.
This bundle of latches — more than three feet (a meter) long — is used to grab visiting spacecraft, and provides power and data. The arm can also move like an inchworm across the space station by grabbing onto special fixtures.
The Canadian-built arm has been in orbit for 16 years. Engineers attribute the recent trouble to wear and tear. The two latching mechanisms, one on each end of the arm, have been used nearly 400 times.
The latching mechanism on the opposite end will be replaced early next year.
It was the first spacewalk for Vande Hei, a rookie astronaut who arrived at the orbiting outpost a few weeks ago.
“Congratulations, my friend, on becoming the 221st human to exit in your own personal spacecraft into the void of space,” said Bresnik, a veteran spacewalker.
“That’s it for all of the tender moments you’ll get from me,” Bresnik joked. “Now back to work.”
“Exactly,” Mission Control radioed. “Slow and steady, and go get ‘er done.”
As the duo worked, they marveled over the views of Earth below and the full moon above.
Six men currently live at the 250-mile-high outpost: three Americans, two Russians and an Italian.
On Wednesday, they marked the 60th anniversary of the Soviet launch of Sputnik, the world’s first artificial satellite, and the beginning of the Space Age.