U.S., British astronauts to perform urgent spacewalk Friday

CAPE CANAVERAL, Fla. -- Astronauts Tim Kopra and Tim Peake will venture outside the International Space Station on Friday to replace a failed voltage regulator and perform several tasks to prepare the outpost for the arrival of two new docking ports.

Peake will become the first Briton to walk in space as the two Tims perform NASA's 35th spacewalk based from the station's airlock. The nearly seven hour spacewalk is expected to begin at 7:55 a.m. EST.

Friday's planned spacewalk will be the 192nd in support of maintenance and repairs to the outpost since construction began in 1998. Kopra, who will be making his second walk in space in four weeks, will be identified as EV1 and sporting red stripes on his space suit, while Peake will be Extra Vehicular 2.

"I am thrilled at this opportunity for a spacewalk," Peake said from 255 miles above the planet. "Right now we are focusing on preparing the tools, equipment and procedures. If the spacewalk is successful, this will restore the International Space Station to 100% of its operational capability."

Space station commander Scott Kelly will assist the spacewalkers in donning and later removing their bulky suits. Kelly and Russian cosmonaut Mikhail Kornienko are currently nine months into a historic one year mission in space, their Soyuz craft set to carry them home in March.

The astronauts prime task will be the replacement of one of the eight Sequential Shunt Units (SSU), each one regulates power from the orbital outpost's solar arrays. NASA states the loss last November of this SSU was not very critical.

"We have eight power channels and we're down one. From a station perspective we could live in this state for quite a while," NASA space station operations manager Kenneth Todd explained on Tuesday. "If we were to have an additional failure in another channel, we'd probably find ourselves a little more strapped, and given the readiness of the team we feel it's about time to go get this work behind us."

Thirty minutes into the spacewalk Kopra, followed soon after by Peake, will begin a long, exhaustive transition to the end of the station's truss to the failed SSU. Peake will carrying the replacement voltage regulator while scaling across the truss segment. In Mission Control near Houston, astronaut Reid Wiseman will orchestrate the work and provide safety notes to the Tims. Wiseman performed a similar SSU replacement in 2014.

"The SSU is a large rectangular box with electrical connectors and alignment pins," European Space Agency spokesperson Julien Harrod said. "After removing the failed unit, Peake will hand the replacement to Kopra for installation."

The electrical repair will begin as the orbiting laboratory moves into darkness -- a time when the solar arrays do not collect electrical current -- and pause during its daylight pass. The space station travels at five miles per second, and takes 91 minutes to complete one orbit of the planet.

The spacewalking duo will work together to unbolt the old regulator and replace it with a new unit. The failed SSU will then be carried back by Peake and stowed inside the Quest airlock for it's return to Earth so engineers can learn how it crashed.

Following the completion of the two hour SSU change out, the astronauts will turn their attention to the retrieval of a broken camera, and will begin laying out electrical and data cables in preparation for the arrival of two International Docking Adapters.

Each Boeing-built IDA will be attached to existing docking ports to enhance the docking capabilities of newly designed spacecraft. The adapters will allow both crewed and uncrewed spacecraft from Boeing and SpaceX a place to dock to the orbiting laboratory.

The second of two completed docking adapters is expected to arrive in April aboard an uncrewed SpaceX Dragon space station resupply craft. The first adapter was launched on June 28 and lost two minutes into the ill-fated flight of a Falcon 9 resupply flight. A replacement IDA is under construction and is planned for launch this December.