Two spacewalking NASA astronauts have been busy today at the International Space Station.

The pair replaced a failed backup computer during a jaunt outside the ISS.

Mission Control called it a “nice and clean” spacewalk and the backup computer is now online.

The astronauts wrapped up their work ahead of schedule, completing the job in just over 90 minutes. The spacewalk was scheduled to take 2.5 hours.

NASA astronauts Rick Mastracchio and Steve Swanson ventured outside the orbiting outpost just before 10 a.m., nearly 40 minutes late. Both have 14 previous spacewalks between them.

Their task was to replace the multiplexer-demultiplexer (MDM) that failed on April 11.

It's a backup computer that routes commands to the systems controlling the station's solar arrays and robotic arm rail car on the ISS' truss or backbone.

In a short time, the failed unit was taken out and the new one installed and powered up.

Both astronauts are now safely onboard the space station.