Wednesday's spacewalk began at 7:13 a.m. EST.
The two astronauts are seasoned astronauts. This is the eighth outside business for Cassidy and Behnken, according to NASA.
Behnken, with NASA astronaut Doug Hurley, took off from the United States and joined Cassidy on the space station on May 31. They were aboard the SpaceX Crew Dragon during the Demo-2 mission.
These spacewalks are the culmination of a series of electrical upgrades that began in January 2017 to replace nickel-hydrogen batteries with new lithium-ion batteries.
This spacewalk, similar to the one that took place last Friday, will focus on replacing the batteries in one of the starboard beam supply channels distant from the station. Because the astronauts completed some of the tasks for this spacewalk in the past week, they will also be focusing on the tasks for future spacewalks, routing the power and Ethernet cables, and working on d other preparations for future power system upgrades.
These cables will provide better views on future spacewalks, according to NASA.
These power system upgrades, however, are nothinglike replacing the batteries in your remote control. The new batteries each have a mass of 428 pounds.
For this second spacewalk, Cassidy will be crew member I and wearing a spacesuit showing red stripes, while Behnken will serve as crew member II in a striped suit. Hurley and Russian cosmonaut Ivan Vagner will help Cassidy and Behnken in their space suits. Hurley will operate the station's robotic arm to support astronauts outside the station.
The battery replacements, which will have a lifespan of 20 years, will place the station in a much better configuration in the long term, said Kenneth Todd, deputy program director of the International Space Station, at a press conference at NASA last week.
Behnken recently discussed the spacewalk and why it's important to replace the batteries, when calling CNN Innovation and Space Reporter Rachel Crane's space station.
"When the space station is in the sun, it collects energy and must be stored when it is in the dark," he said. "And therefore these batteries, as they are cycled over and over again, they wear out and must be replaced. And therefore periodically that maintenance is necessary."
Behnken said he is looking forward to another spacewalk experience.
"I really look forward to seeing the Earth when we have a free moment," he said. "I think every astronaut, when they go on their first spacewalk, they are really focused on trying to do all the activities and do a good job so that they can probably have a chance to do it. another if the opportunity arises.
"But after making a couple and knowing what to expect as you go along, it's important, you know, to take mental pictures, mental pictures, or to remember what it was like to be outside."
