How Astronauts Prepare for a Space Walk at the International Space Station

— -- American astronauts Barry Wilmore and Terry Virts are preparing for their first space walk of Expedition 42 when the duo step outside the International Space Station on Friday.

How does an astronaut prepare for a space walk? Practice.

Terry Virts, who will be taking the first space walk of his career on Friday, tweeted a photo of himself trying out the suit he'll use when he and Wilmore embark on their six-and-a-half hour space walk. It will be Wilmore's second space walk.

The duo will be working on new docking ports for future spacecraft that will arrive at the station. Friday's space walk is one of three that are scheduled to complete assembly work outside of the station.

NASA said today the duo had inspected their rescue jet packs, which would be used in the unlikely event that either astronaut became untethered from the space station.

Virts, who is one of the most active tweeters at the International Space Station, also shared a snap of himself hooked up to various health monitors doing a routine health check-in before his big day.