Two members of Expedition 48, NASA astronauts Jeff Williams and Kate Rubins, ventured outside the station for the second time in as many weeks. Their task was to retract an unused thermal radiator, install a new light bulb and attach high definition cameras on the truss of the International Space Station (ISS).
The Sept. 1 spacewalk started at 7:53 a.m. EDT (11:53 GMT), after the Quest airlock had completely depressurized and the two astronauts spacesuits’ switched to battery power. Williams was designated the lead spacewalker, EV-1, and wore red stripes on his suit. Comparatively, Rubins, EV-2, wore white stripes.
“Welcome back outside,” Williams said to Rubins after floating out of the airlock. This was his fifth Extravehicular Activity (EVA) and Rubins’ second.
“Yeah, good to be out here,” Rubins said.
The first order of business was to retract a thermal radiator on the P6 truss segment called the Trailing Thermal Control Radiator (TTCR), pronounced “ticker.” It is effectively a spare that was deployed years earlier in order to compensate for an ammonia leak.
Once out of the airlock, Williams started toward the work area on the far-port side of the Integrated Truss Assembly, the backbone of the orbiting laboratory. It holds most of the station’s power, cooling equipment, batteries, and orbital replacement units, just to name a few. As he went, he set up tethers for Rubins. Once he was nearly at the site, Rubins began to make her way over.
Once at the site together, Williams got into position below the radiator, while Rubins was above it to watch it as he retracted it with his Pistol Grip Tool (PGT). In essence, the PGT is a power tool designed for spacewalkers.
First, using the PGT, Williams turned a bolt. As it turned, the radiator folded up like an accordion. Once the task was complete, both Williams and Rubins worked together to cinch the ticker down via four bolts. They are not dissimilar to lug nuts on a car tire.
After everything was secure, the two covered the ticker with a thermal blanket, completing the primary task of the EVA.
The secondary tasks of this EVA were to replace a light bulb and place two enhanced HD cameras on an antenna extruding from the P1 truss. To get into a better position to accomplish these goals, Williams took a ride on the robotic Canadarm2.
Japanese astronaut Takuya Onishi, located inside the ISS, took controlled the arm with Williams attached and placed him directly in front of the antenna. Once he arrived, he swapped out the old bulb with the new one and attached the enhanced HD cameras. The new cameras will be used next to the original standard definition camera.
While this was ongoing, Rubins, went back to the airlock to stow some equipment before heading back to the main work area. Her secondary task was to inspect the Solar Alpha Rotary Joint (SARJ), which is a paddlewheel that allows all eight Solar Array Wings to track the Sun.
She also tightened some bolts that were loosened during a previous spacewalk.
After that task was complete, she moved to the P6 truss to uncover a few failed orbital replacement units. This will allow for the Dextre robotic manipulator to grab onto them. A future SpaceX Dragon spacecraft will bring up the replacement boxes to be swapped out. In light of the recent SpaceX pad explosion, it is unclear when the next CRS Dragon will be sent to the outpost.
After the work was finished, the two astronauts made their way back to the airlock using the same path they took to get to the work site. Once back inside and their space suits attached to station power and air, the spacewalk officially concluded. All in all, the total time for this EVA was 6 hours, 48 minutes.
Altogether, 195 spacewalks have been performed in support of assembly and maintenance of the ISS for a total of 1,217 hours, 34 minutes.
After repressurizing the airlock, the two were helped out of their space suits by other members of Expedition 48.
In about four days, Williams, along with two Russian cosmonauts, Aleksey Ovchinin and Oleg Skripochka, will board their Soyuz TMA-20M spacecraft to head back to Earth after 172 days in space.
During his stay, Williams set the all-time U.S. endurance record for most cumulative days in space. His total upon landing will be 534 days over four missions since 2000.
Undocking is currently scheduled for 5:51 p.m. EDT (21:51 GMT) Sept. 6. Landing is expected to follow about three-and-a-half hours later.
Remaining aboard the station will be Rubins, Onishi and Russian cosmonaut Anatoli Ivanishin. They launched to the outpost aboard Soyuz MS-01 back on July 7, 2016.
Ivanishin is set to take over command of the station from Williams a day prior to leaving the ISS. However, Expedition 48 will end and 49 begin only when Soyuz TMA-20M is undocked.
Written by: Derek Richardson
Original source: spaceflightinsider.com