"Looks like we've got a new MDM," Mastracchio said as he finished the job.
A quick test showed the new computer was working fine.
"Oh wonderful," Mastracchio said.
There are 45 MDM computers on the International Space Station, with 21 of them located on the orbiting lab's exterior and the rest installed inside the station's habitable area. Replacing the MDM computer boxes is one of 12 core space station repair skills astronauts learn before launch, NASA officials have said.
Despite their swift work, the spacewalkers did take time to marvel at the bright blue Earth below. At one point, Mastracchio reminded Swanson to take a look down at the sunlit Earth.
"Where are we?" Mastracchio asked Mission Control later. The answer: Over South America.
"A great view," the astronaut replied.