Expedition 66 astronauts Raja Chari and Matthias Maurer ventured outside the International Space Station on Wednesday, performing a spacewalk to carry out repairs and upgrades on the space station.
US EVA-80 marked the 248th spacewalk carried out at the International Space Station, including spacewalks carried out from the Russian Orbital Segment and as part of Space Shuttle missions. It is the last spacewalk before the departure of Soyuz MS-19 next Wednesday, which marks the handover from the current Expedition 66 to Expedition 67.
The spacewalk began at 12:32 UTC lasted nearly seven hours, a fairly typical duration for most ISS spacewalks.
The astronauts carried out a number of maintenance and upgrade tasks on the station’s external hardware, including fitting hoses on a radiator module, installing a power and data cable on the European Space Agency (ESA) Columbus module, and replacing an external camera.
NASA astronaut Chari, designated EV-1 for Wednesday’s spacewalk, identified by red stripes on his spacesuit, was wearing Extravehicular Mobility Unit (EMU) 3004. In the EV-2 role, Maurer, a European Space Agency astronaut, was wearing EMU 3015 without the identification stripes.
A problem with the helmetcam did cause a one hour delay to the tasks, but none of the primary goals of the EVA.
The EMU spacesuits were developed during the Space Shuttle program. As always, both astronauts’ suits will be equipped with Simplified Aid For EVA Rescue (SAFER) recovery aids, to provide an emergency maneuvering capability so they can return to the ISS in the unlikely event their tethers should break.
Chari (left) and Maurer (right) carry out a spacesuit fit check with the aid of Thomas Marshburn (credit: NASA)
US EVA-80 was the fourth spacewalk of Expedition 66, following US EVAs 78 in December and 79 earlier this month. A Russian EVA was also performed from the Poisk module in January. With Expedition 66 due to hand over to Expedition 67 next Wednesday when Soyuz MS-19 returns to Earth, it is expected to be the last EVA of the current increment.
Wednesday’s spacewalk was the second of Raja Chari’s career, following US EVA-79 last Tuesday, and the first for Matthias Maurer. While Chari spent most of the EVA riding the station’s Canadarm2 robotic arm, Maurer was required to translate across much of the US segment of the station.
Maurer stated in an ESA press release “I really do have to do a complete tour of the space station. It is a motley mix and I’m totally looking forward to it”. He will be the twelfth European Space Agency astronaut and the fourth German to conduct a spacewalk at the ISS, after Thomas Reiter, Hans Schlegel, and Alexander Gerst.
The astronauts began and ended the spacewalk from the Quest airlock module, which is used for all US EVAs carried out at the station. Raja Chari’s main focus was carrying out repairs to a Radiator Beam Valve Module (RBVM), while Maurer worked on installing cables outside ESA’s Columbus module.
The RBVMs help to route ammonia through the space station’s radiators, providing cooling for onboard systems, including vital electronics. Spacecraft must use radiators to help dissipate heat as in the vacuum of space air circulation cannot be used to take heat away as it would on Earth.
The RBVM jumpers were inspected on-orbit in 2017 before their refurbishment (credit: NASA)
There are six of these modules on the P1 and S1 truss elements. The RBVMs are vital items of cooling hardware, controlling the flow of ammonia to and from the radiator assemblies, which themselves extend from the space station’s truss. The RBVMs can monitor pressure, temperature, and valve position, and can also vent ammonia during contingency situations. They also help to control pressure in the External Active Thermal Control System (EATCS) cooling loop.
A pair of ammonia line jumper hoses were removed from one of the RBVMs during a previous EVA after a small leak had been detected. These were returned to Earth for refurbishment, before being transported back to the ISS aboard a Dragon Cargo spacecraft. Chari reinstalled these jumpers onto the RBVM while mounted to a foot restraint on Canadarm2. He also installed two quick disconnects that will be used to provide power to a heater.
Meanwhile, Matthias Maurer connected a power and data cable to the Bartolomeo external science platform, which was installed on the Columbus module last year.
Bartolomeo hosts experiments that need direct access to the vacuum of space, such as investigating how material samples are affected by long-duration exposure to space. Maurer installed the last connections needed to make the platform fully operational. He also prepared the platform for experiments to be installed remotely using the station’s robotic arm.
The Bartolomeo facility (bottom right) attached to the Columbus module (credit: Airbus)
Another key objective for Wednesday’s EVA was to replace an external view camera on the P1 truss, a task for which Chari and Maurer will work together. Cameras are mounted at various points on the exterior of the ISS to document station activity and conditions. The new camera, installed on the Camera Port 8 site, will have an improved two-way data rate to the ground.
After the camera installation, Chari installed T-handle tools on the port radiator grapple bar to aid astronauts on future EVAs. Later he and Maurer completed the work on the RBVM by stringing a power cable to the module where Chari had installed jumpers earlier.
Other tasks scheduled for US EVA-80 included Maurer securing a loose insulation blanket on the Japanese Kibo science module, and making his way to Truss P4, to release bolts connecting orbital replacement units on that truss.
Maurer’s task was documented as then re-torquing the bolts at a lower setting. This will allow the Canadarm to more easily remove and replace these units as needed. He was also set to adjust an electrical connector on the S0 Truss mounted to the Destiny module so that it can once again provide power to a component.
Due to the camera issues at the start of the spacewalk, some get-ahead tasks could not be performed on this EVA and will be left for future spacewalks.
(NASA astronaut Raja Chari works outside the ISS during US EVA-79 earlier this month. Credit: NASA)