In 2014 Boeing and SpaceX were awarded contracts worth some $6.8 billion to develop commercial crew transportation systems for the ISS. SpaceX is building a crewed version of its Dragon cargo capsule, called Crew Dragon, and Boeing is constructing a crew capsule called the CST-100 Starliner.
The IDA-2 adapter, the second to be built, will allow new spacecraft to dock with the station, beginning in 2017. Spacecraft using the International Docking Standard, including NASA's Orion capsule, will be able to attach to the ISS.
The docking adapter was launched from Cape Canaveral atop a Falcon 9 rocket on July 18 and has remained, until now, inside the Dragon's external trunk section.
In four previous spacewalks, astronauts completed preparatory steps for the upcoming installation, including positioning dozens of meters of power and connectivity cabling for the docking adapter. The two astronauts will be assisted in their spacewalk by Takuya Onishi of the Japanese Aerospace Exploration Agency, who will monitor the progress from inside the ISS during the installation.
"There's a very coordinated interplay between the external crew outside, Tak on the inside, and the ground doing the commanding," said Zeb Scoville, the spacewalk flight director, during a NASA briefing.
The installation process will be aired by NASA TV beginning 6:30 a.m. EST (10:30 GMT).
