NASA astronauts Kate Rubins and Jeff Williams are performing a six-and-a-half hour spacewalk today, in order to install a new international docking adapter — or IDA — to the outside of the International Space Station. Things get underway around 8:05AM ET, and you can watch NASA's coverage of the event in the livestream above.

The IDA is a key element of NASA’s Commercial Crew Program

The IDA is a key element of NASA’s Commercial Crew Program. That’s the initiative in which private companies create "space taxis" for NASA, to ferry the agency’s astronauts to and from the space station. For the program, SpaceX is building a crewed version of its Dragon cargo capsule, called Crew Dragon, and Boeing is building a brand-new crew capsule called the CST-100 Starliner. Those spacecraft are slated to carry astronauts to the ISS for the first time in late 2017 and early 2018, respectively. And when they arrive at the station, they’ll dock with the IDA.

The docking adapter just got to the space station on July 20th, after launching on one of SpaceX’s Falcon 9 rockets. It didn’t travel inside SpaceX’s pressurized Dragon capsule, though, which usually houses all the cargo bound for the station. Instead, the adapter was transported inside the Dragon’s trunk — the unpressurized structure attached to the end of the capsule that provides support and houses the vehicle’s solar panels. The IDA has mostly remained in the trunk since its arrival, until it was freed on Wednesday, August 17th. The station’s robotic arm removed the IDA from the trunk and placed the adapter about three feet away from the port it will be connected to.

Now that the IDA is in position, Rubins and Williams will exit the ISS and go through the complex process of hooking up the adapter to its port. Fortunately, lots of preparations have already been made to help the installation run smoothly. In four previous spacewalks, astronauts positioned all the necessary cables that Rubins and Williams will attach to the docking adapter to give it power and connectivity. Additionally, the two astronauts will have help from Takuya Onishi of the Japanese Aerospace Exploration Agency, who will remain inside the ISS during the spacewalk. After helping them to suit up, Onishi will manage a control panel inside the station that will help to physically connect the IDA to its port. "There’s a very coordinated interplay between the external crew outside, Tak on the outside, and the ground doing the commanding," said Zeb Scoville, the spacewalk flight director, during a NASA briefing.

This will be the fourth spacewalk for Williams and the first for Rubins

This will be the fourth spacewalk for Williams, who has been traveling to space since 2000. For Rubins, the spacewalk will be her first, though she has been training for this particular mission for years on the ground, according to Scoville. During the installation, the astronauts will be able to drink water from a 36-ounce drink bag, but neither will have any food to eat.

This is also the first spacewalk NASA has done since January. During that outing, NASA astronaut Tim Kopra and Tim Peake of the European Space Agency replaced a failed voltage regulator that had cut off one of the station’s power channels. However, that spacewalk didn’t go exactly according to plan. The walk ended two hours early after Kopra noticed a small water bubble had formed inside his helmet. NASA was worried about the same issue happening for this spacewalk, but the agency thinks they know what went wrong. The problem may have had to do with blockage in the spacesuit’s sublimator, along with some operational procedures that may have produced too much condensation. NASA has taken steps to make sure this doesn’t happen again during Friday’s installation, according to Kenneth Todd, an ISS program representative.

Originally, the first IDA installation was supposed to have taken place last summer. An adapter was set to arrive at the station in June of 2015, but it was destroyed when the Falcon 9 rocket that was carrying it disintegrated during launch. If that launch had been successful, the IDA that is now at the ISS would have been the second adapter and the station would have two functioning docking ports ready before the first Commercial Crew flights got underway. Now, NASA may only have one ready before those flights happen, which the space agency is prepared for. Another IDA is currently being built by Boeing and will likely go up on another SpaceX launch in early 2018, according to NASA.