Astronauts take a spacewalk to repair robotic arm
Expedition 53 Commander Randy Bresnik and Flight Engineer Mark Vande Hei wrapped up the first of three spacewalks planned for the next two weeks. The October 5, 2017, spacewalk was nearly seven hours long and saw the replacement of one of the two Latching End Effectors (LEE) on the International Space Station’s robotic arm.
Starting at 8:05 a.m. EDT (12:05 GMT) Oct. 5, the astronauts switched to suit-battery power on their Extravehicular Mobility Units to begin U.S. EVA-44.
Once outside, the two made their way to the P1 truss segment on the port side of the outpost. There, already prepositioned, was the LEE-A side of the robotic arm. After installing foot restraints on the truss segment, the two began working to remove the end effector.
The LEE is attached to the arm wrist joint via six Expandable Diameter Fasteners. These were released by the astronauts using the space-grade equivalent of a power drill called a Pistol Grip Tool (PGT).
Once the first two fasteners were released, the LEE was commanded to rotate so that the spacewalkers could reach the other four. Once that maneuver was completed, the robotic arm was powered down.
With no problems, the duo removed the 440-pound (200-kilogram) end effector and tethered it to a temporary stowage location near the work area. The new LEE, located on the Mobile Base Unit, was removed from its current location and attached to the arm in a reverse fashion. Once four of the bolts were driven using the PGT, ground teams powered the robotic arm back on. This allowed for a 10-minute break for the astronauts.
After the power-up, the remaining bolts were driven and the primary task of the spacewalk was completed, some three hours into the EVA. While the duo began cleaning up their workspace and attaching the old LEE on the Mobile Base Unit, ground teams decided to give each astronaut a get-ahead task.
The two tasks involved removing a protective cover from a spare Direct Current Switching Unit, allowing it to be removed robotically in the future, and to prepare a Flex Hose Rotary Coupler for future operations. By the time those were finished, it was time to call it a day. The two astronauts made their way back to the airlock to conclude the spacewalk after 6 hours, 55 minutes outside the outpost.
Source: Spaceflight Insider