Spacewalk underway for space station maintenance, upgrades

Two astronauts floated outside the International Space Station Wednesday for a spacewalk to install refurbished ammonia jumpers in the lab’s cooling system, to replace a high-definition camera and to make power and data connections on a European instrument platform.

NASA’s Raja Chari and Matthias Maurer, a German astronaut with the European Space Agency, also plan to carry out a variety of other maintenance tasks and upgrades, working independently through most of the spacewalk, which NASA refers to as an extra-vehicular activity, or EVA.

“We’re actually going to have our crew members at separate locations for the majority of the EVA,” said spacewalk flight director Paul Konyha. “In fact, it’s actually going to seem like there’s two EVAs happening at once at the same time.

“Our first EVA crew member (Chari) is going to be on the robotic arm for the majority or the entirety of the EVA. Our second crew member (Maurer) will be in free float, traversing many locations to accomplish many of the tasks that we have scheduled.”

Floating in the Quest airlock, the astronauts switched their spacesuits to battery power at 8:32 a.m. EDT to officially kick off the 248th spacewalk in ISS history, the third so far this year, the second for Chari and the first for Maurer.

NASA astronaut Raja Chari (left) and ESA astronaut Matthias Maurer (right) in their spacesuits for a rehearsal ahead of Wednesday’s spacewalk. Credit: Mattias Maurer/ESA/NASA

Chari, anchored to the end of the space station’s robot arm, plans to install the ammonia jumpers, work with Maurer to attach and connect the TV camera and attach two handling fixtures to an external radiator assembly.

Maurer will float from work site to work site, making power and data connections on the European Bartolomeo instrument platform, tying down a pulled-up insulation blanket on the Japanese Kibo module and helping Chari connect the new TV camera.

He also plans to carry out a variety of other tasks, including work to loosen bolts in a solar array electronics assembly to facilitate future component changeouts and to run a power cable to a coolant pump module.

The space station circulates ammonia through heat exchangers out to six radiators, three on each side of the lab’s power truss, to dissipate the heat generated by the station’s electronics. The ammonia is routed to the radiators through hoses from “radiator beam valve modules,” or RBVMs, part of a system that can be rotated with respect to the sun to maximize cooling.

In 2017, a slight leak was detected in jumpers running between one radiator panel and an RBVM. The hoses were bypassed, removed, taken back to Earth, refurbished and relaunched for installation by, as it turns out, Chari.

The spacewalk is expected to last about six-and-a-half hours.