Wednesday was the second in a series of International Space Station spacewalks where the astronauts worked on upgrading the exterior of the ISS.
It was a mission made possible by a lot of preparation.
"Spacewalks are one of the more dynamic things we do probably one of the more dangerous things we do other than launch and landing,” said NASA Spokesperson Brandi Dean. “And it's also one of the hardest things that I hear astronauts say -- that's the hardest part of their job."
Spacewalks are physically and mentally demanding. NASA astronauts spend a lot of time on land before they even make it to the International Space Station preparing and training.
"Underwater is one of the ways we do it we also have a harness they get into so they can experience gravity to some extent,” Dean said. “And studying, they spend a lot of time studying what exact moves they're supposed to be making, what connections to expect what handrails they'll be using to get from one place to another, so it is a lot of time and dedication."
NASA astronaut Kjell Lindgren spoke to NBC Connecticut in May ahead of the historic SpaceX Crew Dragon launch. He spoke about his experience in space, flying his first mission in 2015, spending 141 days on the International Space Station, and completing 2 spacewalks.
"The ability to look down at the earth to find places where I've lived where I have friends, the first view through my helmet visor as I did a spacewalk,” Lindgren said. “And then I think on top of all of those extraordinary experiences one of my favorite memories was reuniting with my family."
Through social media and NASA TV, Wednesday's mission was broadcast live and viewers were able to watch the astronauts switch out old batteries on the exterior of the ISS for new ones.
And 6 hours later, the mission was complete and the astronauts were safely helped back on board by a familiar face - Doug Hurley - who made history with Bob Behnken in May when the two arrived at the International Space Station by way of SpaceX’s Crew Dragon.