NASA astronauts Christina Koch and Jessica Meir will venture outside the orbiting outpost at about 7:50 a.m. ET Friday and spend over five hours replacing a broken battery charger, or BCDU. NASA will livestream the spacewalk starting at 6:30 a.m. ET.

The units have previously been replaced using a robotic arm, but the newly failed unit is too far away for it to reach.

The units regulate how much energy flows from the station's massive solar panels to battery units, which are used to provide power during nighttime passes around Earth. Three previous spacewalks had been planned to replace lithium-ion batteries, but those will be rescheduled until the latest BCDU issue is resolved.

The hardware failure does present some concern, especially since another BCDU was replaced in April and there are only four more backups on station. In total, there are 24 operational BCDUs.

The battery charger failed after Koch and a male crewmate installed new batteries outside the space station last week. NASA put the remaining battery replacements on hold to fix the problem and moved up the women's planned spacewalk by three days.

All four men aboard the International Space Station will remain inside. 

Friday's spacewalk will be Koch's fourth and Meir's first. 

Koch and Meir will have some time leftover during their extravehicular activity, or EVA, to finish additional tasks like hardware installations for the European Space Agency.

The planned EVA comes almost seven months since the first all-female spacewalk was canceled due to a lack of properly sized spacesuits for astronauts Koch and Anne McClain. Astronaut Nick Hague ended up joining Koch instead.

But this time, the right spacesuit hardware is in place.

NASA, meanwhile, is asking schoolteachers to share photos of their students celebrating "HERstory in the making." The pictures might end up on the spacewalk broadcast.

Russia holds claim to the first spacewalk in 1965 and also the first spacewalk by a woman in 1984. The U.S. trailed by a few months in each instance.

As of Thursday, men dominated the spacewalking field, 213 to 14.

Meir, a marine biologist who arrived at the orbiting lab last month, will be the 15th female spacewalker. Koch, an electrical engineer, is seven months into an 11-month spaceflight that will be the longest by a woman.

USA Today

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