NASA Astronauts Wiseman and Wilmore Complete Spacewalk (EVA)

NASA astronauts Reid Wiseman and Barry Wilmore work outside the International Space Station during a spacewalk on Oct. 15, 2014.

Credit: NASA TV

Two NASA astronauts working outside the International Space Station raced against the clock during a spacewalk today (Oct. 15).

NASA's Reid Wiseman and Barry "Butch" Wilmore performed a 6.5-hour-long spacewalk that included one particularly tricky task that had to be started and completed when the orbiting outpost was in orbital night.

Wilmore and Wiseman managed to remove and replace a power regulator that shorted out in May during the short amount of time when the station experienced night.

"Whoop!" one of the astronauts exulted after the replacement regulator was installed. The regulator, which is used to regulate power from one of the station's solar arrays, needed to be changed out in order to restore the station to full power.

Mission controllers watched a clock ticking down the time the astronauts had to complete the task.

The spacewalk officially began at 8:16 a.m. EDT (1216 GMT) and ended 6 hours and 34 minutes later.

The two astronauts also removed a faulty camera from the outside of the station and installed a new one.

Wilmore and Wiseman also moved some equipment to get ready for the eventual relocation of the station's Permanent Multipurpose Module (PMM) in 2015, NASA officials said.

PMM was built by the Italian Space Agency and is attached to the Earth-facing side of Unity module.

Despite their hard day of work, the astronauts still had time to do a little sightseeing while outside the space station.

They both got some good views of Earth during the spacewalk.

"That is amazing," one of the astronauts said when the spacewalkers spotted a possibly erupting volcano while flying above Earth.

"I see Cairo," Wiseman said during a pass over Egypt. "Can't quite make out the pyramids, though."

The PMM needs to be moved in order to make way for a pair of commercial crewed vehicles that could begin flying astronauts to the orbiting outpost as early as in 2017.

Astronauts will also need to install a set of international docking adaptors that should fly to the station in 2015 for the commercial vehicles.

The two October spacewalks kick off a series of EVAs (extravehicular activities) designed to make way for the new private spaceships once they start delivering astronauts to the station.

"We're going to be doing the things we need to do on these EVAs to prep for moving some modules around," Kenny Todd, space station integration operations manager, said during a news conference before the spacewalks.

"All that is in preparation for being able to support future [commercial] crewed vehicles coming to [the] station. We're trying to get out in front of that … We'll be prepping for moving modules; we'll be installing a new docking adapter system. All of that will be happening throughout the next several months on board the station."