Two International Space Station (ISS) astronauts ventured outside the outpost on the first of three planned spacewalks to prepare for the arrival of a second docking adapter for the Commercial Crew Program. The 6.5-hour long spacewalk began at 7:24 a.m. EDT (11:24 GMT) March 24, 2017.
For extravehicular activity (EVA) 40, Expedition 50 Commander Shane Kimbrough and Flight Engineer Thomas Pesquet were tasked with disconnecting cables and electrical connections on Pressurized Mating Adapter 3 (PMA-3), located on the port side of the Tranquility module.
This adapter was used for two Space Shuttle flights in 2000 and 2001. Endeavour and Atlantis docked with PMA-3 during STS-97 and STS-98 respectively to allow for the P6 truss and Destiny laboratory to be attached to the space station.
PMA-3 has since been stored on various ports around the space station since 2001 to make room for other modules. It has been in its current position since February 2010.
Whereas the Pressurized Mating Adapters were used to connect to spacecraft with the APAS-95 docking interface, namely those used by the Space Shuttle, future commercial crew spacecraft launching in 2018 will utilize the NASA Docking System. As such two International Docking Adapters were developed. The first one, IDA-2 (IDA-1 was lost during the CRS-7 launch mishap), was attached to PMA-2, which is located at the forward end of Harmony.
Once PMA-3 is in its new location and power and data cables are connected during the next couple spacewalks, IDA-3 can be launched, likely aboard the CRS-16 Dragon mission in 2018.
For EVA-40, Kimbrough was the lead spacewalker, EV-1, while Pesquet was EV-2. After leaving the airlock, the duo separated to conduct their respective tasks.
Kimbrough went to the S0 truss to change out a computer processor box called the External Control Zone 2 (EXT-2) Multiplexer-Demultiplexer (MDM). There was nothing wrong with the device, it was just being replaced with a more capable version called EPIC MDM.
Once that task was completed, Kimbrough took the EXT-2 MDM to the airlock before heading over the the port side of the Tranquility module for the primary task of EVA-40. He disconnected power and data cables to allow PMA-3 to be relocated on March 26.
Kimbrough’s third task was to replace two cameras on the Japanese module’s exposed facility. One was on the Japanese robotic arm while the other was on the forward side of the facility. Once he finished those tasks, he was able to perform one get-ahead task – replacing a failed light on a Crew Equipment Translation Aid cart.
Meanwhile, Pesquet’s primary job for this spacewalk was to lubricate a Latching End Effector (LEE) on the station’s Special Purpose Dextrous Manipulator called “Dextre.”
To accomplish this, Pesquet had to grab a foot restraint and an extender on a pallet next to the airlock. He then moved to the P1 truss segment where he inspected a radiator for any indication of a leak. While patting various flex hoses looking for ammonia flakes, high-definition video was recorded for engineers on the ground to pore over.
After that was done he moved to the S0 truss to begin lubricating the Dextre LEE. On previous spacewalks, the two LEE’s on the robotic Canadarm2 were also greased as part of regular maintenance.
The tool Pesquet used was called a BLT, or Ballscrew Lubrication Tool. It is essentially a rod that has a cradle that grease is applied to. The rode is then inserted into the main cavity of the LEE as well as the four latches along the side where the astronaut will rub the lubricant onto.
Once lubrication was complete he began to clean up his work area before heading over to the airlock to join Kimbrough who also finished all of his tasks.
When both were securely inside the airlock, and hooked up to ISS power and cooling, Pesquet locked the hatch and re-pressurization began, officially ending EVA-40 at 1:58 p.m. EDT (17:58 GMT) after 6 hours, 34 minutes.
This was the 198th spacewalk in support of space station assembly and maintenance, bringing the total EVA time to 1,238 hours. Additionally, this was the third spacewalk for Expedition 50 (the first two occurred in January 2017).
Kimbrough completed his fifth EVA bringing his cumulative spacewalking time to 31 hours, 56 minutes. Pesquet has a total EVA time of 12 hours, 32 minutes over two spacewalks.
The next task will be for ground-based robotics teams to command Canadarm2 to grab onto and relocated PMA-3 to the space-facing port of Harmony at the front of the station. Then on March 30, EVA-41 will take place, this time with Kimbrough and Flight Engineer Peggy Whitson.
The EVA-41 duo will work to reconnect PMA-3 cables and remove a thermal cover to allow for IDA-3 to be attached to in 2018. Additionally, shields will be placed onto the port that the module vacated.
Written by: Derek Richardson
Original source: spaceflightinsider.com