Three pivotal and record-setting periods of Extravehicular Activity (EVA) are scheduled to occur from the International Space Station (ISS) over the coming weeks, according to a news conference, held at the Johnson Space Center (JSC) in Houston, Texas, earlier today (Wednesday, 22 March). ISS Operations Integration Manager Kenny Todd and NASA Flight Director Emily Nelson were joined by the Spacewalk Officers for the three EVAs—Sarah Korona, John Mularski and Alex Kanelakos—to outline plans which will see a major reconfiguration of the station, ahead of Commercial Crew operations. Designated U.S. EVAs 40, 41 and 42, the three 6.5-hour spacewalks will occur on Friday, 24 March, Thursday, 30 March, and Thursday, 6 April.
Current plans are for all three U.S. Orbital Segment (USOS) crew members to make two spacewalks apiece. Expedition 50 Commander Shane Kimbrough will lead EVA-40 with Flight Engineer Thomas Pesquet, and will also lead EVA-41 with Flight Engineer Peggy Whitson. For the third and final spacewalk, Whitson will lead EVA-42 with Pesquet. Assuming all goes according to plan, this busy run of activity will end with Whitson setting a new record for the greatest number of EVAs (and the largest number of spacewalking hours) ever performed by a woman and will include the 200th EVA in support of ISS construction and maintenance.
At present, inaugural unmanned missions by Boeing’s CST-100 Starliner and SpaceX’s Crew Dragon are not expected until early 2018, followed by a pair of piloted test flights—featuring NASA shuttle and ISS veterans Sunita Williams, Eric Boe, Doug Hurley and former Chief Astronaut Bob Behnken—the following summer. Satisfactory completion of these milestones is expected to lead to the first “operational” Post-Certification Mission (PCM) as soon as September 2018. As outlined last fall by AmericaSpace, this represents a delay of around a year beyond the original timeline and is attributable to ongoing technical and software issues with the Commercial Crew vehicles.
In order to enable future CST-100 Starliners and Crew Dragons to interface with the space station, a pair of Boeing-built International Docking Adapters (IDAs) will be installed onto the Harmony node. The “primary” IDA-1 would be attached to Pressurized Mating Adapter (PMA)-2 on the forward “end” of the node, whilst the “backup” IDA-2 would be situated on PMA-3 on its space-facing (or “zenith”) side. Unfortunately, IDA-1 was lost in a June 2015 launch accident, forcing NASA to repurpose IDA-2 as the new “primary” port. After many delays, IDA-2 was successfully launched in July 2016 and installed onto PMA-2, during a combined EVA/robotics operation a few weeks later. Taking the place of the “backup” docking port will be a new IDA-3. This is currently being built from around 300 spare parts and IDA-3 will fly aboard SpaceX’s CRS-14 Dragon in early 2018.
Before IDA-3 arrives, however, it is necessary for PMA-3 to be relocated from its current perch on the station’s Tranquility node to its final Commercial Crew location atop Harmony. That relocation will be principally controlled by the Robotics Officer (ROBO) in the Mission Control Center (MCC) at JSC, although it will require the EVA and “intravehicular” support by the Expedition 50 crew for internal reconfiguration and external cable disconnections and reconnections. Original plans called for the PMA-3 relocation to occur in October 2015, but the IDA-1 failure triggered a delay of almost 18 months. When the adapter is detached by means of the station’s 57.7-foot-long (17.6-meter) Canadarm2 on Thursday, 30 March, it will be its first movement to a new location in over seven years.
Launched aboard shuttle Discovery in October 2000, PMA-3 was originally installed on the nadir face of the Unity node. A few weeks later, it supported the arrival of shuttle Endeavour on STS-97 and was used for only one more spacecraft docking, welcoming Atlantis and her STS-98 crew in February 2001. PMA-3 was then relocated by the STS-102 astronauts in March 2001 from the nadir to the port side of Unity, permitting the temporary installation of the Leonardo Multi-Purpose Logistics Module (MPLM). With the rapid expansion of the ISS and the addition of new pressurized modules, PMA-3 was moved back to Unity nadir in August 2007, ahead of the arrival of the Harmony node, and in early 2009 returned once more to Unity nadir. Its most substantial move, however, came in January 2010, when it was transferred from Unity to a temporary spot at Harmony zenith, where it waited for the arrival of Tranquility. During Endeavour’s STS-130 mission in February 2010, PMA-3 was moved to its current position at the port-facing end of the new node.
Efforts to prepare PMA-3 for its move to Harmony zenith got underway several weeks ago, when the Expedition 50 crew removed items stored inside the adapter, as well as the Intermodular Ventilation (IMV) valve which connects it to Tranquility. Yesterday (Tuesday), the astronauts participated in a briefing, which offered refresher training on their Extravehicular Mobility Unit (EMU) space suits, procedures and hardware. They also performed Robotics On-board Trainer (ROBoT) sessions, verified the functionality of their Simplified Aid for EVA Rescue (SAFER) backpacks and installed batteries in EMUs #3006 and #3008. Current plans are for Kimbrough/Pesquet to complete EVA-40, with Kimbrough/Whitson executing EVA-41 and Whitson/Pesquet teamed together for EVA-42. According to NASA’s Rob Navias, Kimbrough will wear #3008 for EVA-40 and 41, with Pesquet and Whitson clad in #3006. For EVA-42, Whitson will don #3008 and Pesquet will wear #3006.
Kimbrough (designated “EV1”, with red stripes on the legs of his space suit for identification) and Pesquet (“EV2”, wearing a pure white suit) will kick off EVA-40 at 8 a.m. EDT Friday. During their 6.5 hours outside the station, they will disconnect cables and electrical connections on PMA-3 to prepare for relocation. Additionally, the spacewalkers will install a new computer relay box with advanced software onto the S-0 truss, inspect a suspected ammonia leak on a radiator valve, replace cameras on the Japanese Kibo facility and lubricate the Latching End Effector (LEE) of the Dextre robotic “hand” aboard Canadarm2. Earlier today, Jessica Meir—one of NASA’s most recently-selected astronauts—revealed on Twitter that she will be at the Capcom’s console during EVA-40. “Excited to be the #Mission Control voice 4 @astro_kimbrough @Thom_astro @Space_Station #spacewalk Friday,” she tweeted.
Satisfactory completion of Friday’s EVA-40 is expected to set the stage for the PMA-3 relocation, which will be ground-commanded and overseen by Flight Director Emily Nelson and ROBO. “No crew involvement in the actual relocation,” NASA’s Dan Huot told AmericaSpace, earlier this week, “other than leak checks.” Originally scheduled for 30 March, the physical disconnection of the 2,650-pound (1,200 kg) adapter is now scheduled for 12:45 p.m. EDT on Sunday, 26 March, and should be berthed atop the Harmony node a little under four hours later, at 4:30 p.m.
This will allow Kimbrough and Whitson to venture outside the ISS for EVA-41 on 30 March, during which they will reconnect cables and electrical connections between PMA-3 and the Harmony zenith interface. The spacewalkers will then support a multitude of other tasks, including installing a second relay box onto S-0, as well as shields onto PMA-3 and over the now-vacant Common Berthing Mechanism (CBM) port on Tranquility. Finally, on 6 April, Whitson and Pesquet will replace an avionics box on ExPRESS Logistics Carrier (ELC)-4 on the nadir face of the station’s starboard Integrated Truss Structure (ITS). The replacement avionics box will launch aboard Orbital ATK’s OA-7 Cygnus cargo ship on Monday, 27 March.
These three excursions are designated U.S. EVAs 40, 41 and 42, but when Whitson and Pesquet return inside the Quest airlock on 6 April, they will wrap up the 200th spacewalk dedicated to station construction and maintenance. Since the initial ISS-related EVA by STS-88 astronauts Jerry Ross and Jim Newman, way back in December 1998, a total of 121 men and women from nine sovereign nations have toiled on the grandest engineering challenge in human history. Among their ranks have been the first national spacewalkers from Canada, Sweden and Italy, together with the longest EVA of all time. As well as marking Whitson out as the oldest female spacewalker, the ISS era has also seen Russian cosmonaut Pavel Vinogradov secure the world record for the oldest spacewalker. He was 59 when he headed out of the airlock, back in April 2013.
At the time of writing, Whitson and fellow NASA astronaut Sunita Williams have both performed seven EVAs, more than any other woman. Yet in terms of EVA hours, Whitson sits in second place. Her tally presently stands at 46 hours and 18 minutes, slightly behind Williams’ 50 hours and 40 minutes. As soon as she departs the Quest airlock on 30 March, Whitson will thus become the first woman to perform as many as eight EVAs. About 4.5 hours into EVA-41, she will exceed Williams to become the most seasoned female spacewalker of all time. And by the time Whitson returns inside the ISS on 6 April, wrapping up her ninth career EVA, she will have totaled more than 59 hours outside a spacecraft. This promises to set her in third place—behind U.S. astronaut Mike Lopez-Alegria and Russia’s Anatoli Solovyov—on the world list of most experienced spacewalkers.