Expedition 64 spacewalkers Kate Rubins and Victor Glover have completed a grueling session of Extravehicular Activity (EVA) outside the International Space Station (ISS) to prepare for an extensive campaign of solar array upgrades later this year and throughout 2022.
The two astronauts, both of whom were making their third career spacewalks, labored—albeit with some difficulty—to assemble a Modification Kit on the station’s outboard P-6 truss. Sunday’s EVA was the first to be carried out entirely by members of NASA’s “Artemis Team”, who may one day leave their bootprints in lunar dust. And with a cumulative 19 hours and 20 minutes of spacewalking time under his belt, Glover now sits in third place behind Winston Scott and Bob Curbeam for the greatest number of EVA hours by an African-American astronaut.
Assisted by Expedition 64 crewmates Mike Hopkins and Soichi Noguchi, the two spacewalkers arose early and were ahead of the timeline as they suited-up inside the “equipment lock” of the Quest airlock. Rubins and Glover participated in standard In-Suit Light Exercise (ISLE), flexing their arms and legs to speed up their metabolic rates and help rid their bloodstreams of excess nitrogen.
Hopkins and Noguchi helped them to don not only their Extravehicular Mobility Units (EMUs), but also the Simplified Aid for EVA Rescue (SAFER) backpacks, which the astronauts might use as a self-rescue tool, should they become physically separated from the station. At length, they were shoved, equipment and all, into the outer “crew lock” and hatches between the two locks were sealed to begin the process of depressurization to near-vacuum.
Overseeing today’s activity—designated “EVA-71”, the 71st spacewalk in U.S.-built suits, and conducted in the absence of the Space Shuttle, since February 2002—was a highly experienced Mission Control team at the Johnson Space Center (JSC) in Houston, Texas. Leading the “suit-up shift” was veteran Flight Director Anthony Vareha.
“Assembling a one-person spaceship is delicate work,” Mr. Vareha tweeted. “In most ways, @NASA_Astronauts are normal people, but I’ll grant that they do put their space suit pants on two legs at a time.” And the lengthy EVA itself was led by Flight Director Marcos Flores, Spacewalk Officer Art Thomason and Ground Intravehicular (IV) communicator, astronaut Frank Rubio.
Rubins and Glover transferred their suits’ life-support utilities onto internal battery power at 6:12 a.m. EST, formally kicking off what was expected to be 6.5 hours of activity. With Rubio’s calm voice in their earpieces, they set to work configuring tools and tethers and performing “buddy checks” of each other’s suits, before heading to work.
Their primary goal was to set up the struts of the first Modification Kit on the P-6 truss, which will support an upgraded set of ISS Roll-Out Solar Arrays (iROSAs), currently scheduled to launch aboard SpaceX’s CRS-22 Dragon cargo mission in May. As previously outlined by AmericaSpace, six iROSA arrays will partially cover (and thus “shadow”) six of the eight “legacy” solar arrays which were installed by successive shuttle crews between December 2000 and March 2009.
As part of the iROSA upgrade, both power channels on the station’s S-4 truss will receive new arrays, as will one channel apiece on the P-4 and S-6 trusses. But the primary focus of Sunday’s work was on the P-6 truss, which is by far the oldest, having been installed by the STS-97 shuttle crew way back in late 2000. Its twin Solar Array Wings (SAWs)—designated Power Channels 2B and 4B—were to be fitted with a Modification Kit that will allow the iROSAs to be installed later this year.
“This specific iROSA configuration was selected after careful consideration to balance observed degradation in the legacy solar arrays with the anticipated demand on each channel,” NASA’s Gary Jordan previously told AmericaSpace. When all six iROSAs are in place, they will function in tandem with the “unshadowed” element of the legacy arrays and are expected to afford the ISS a power hike from 160 kilowatts to 215 kilowatts.
The 330-pound (150 kg) Modification Kit—delivered last fall aboard Northrop Grumman Corp.’s NG-14 Cygnus cargo ship and temporarily stored in the end-cone of the Leonardo Permanent Multipurpose Module (PMM)—was too large to bring directly outside, so was carried in pieces in an 8-foot-long (2.4-meter) bag and passed out by Glover. The two astronauts made their way along the expansive Integrated Truss Structure (ITS) to reach P-6, which sits at the furthest-port end of the station. They stowed their bags and Rubins ingressed an Articulating Portable Foot Restraint (APFR) to begin work.
Working initially ahead of the timeline, they set to work on Power Channel 2B and attached a mounting bracket and an upper and lower strut to form the so-called “upper triangle”, which was to be bolted via the Pistol Grip Tool (PGT) onto the P-6 Mast Canister. Unfortunately, at her first attempt, Rubins was unable to fully engage one of the bolts and used a power drill to back it out and re-seat it. She then worked with a ratchet wrench to tighten the bolt, which yielded a safe configuration. NASA expects that the bolt will need to be secured further before the iROSA is installed later this summer.
The spacewalkers next moved to Power Channel 4B and completed the construction of the upper support hardware, securing it to the ISS structure, with an expectation that Rubins and Noguchi will complete this task in another EVA on Friday, 5 March. As for Sunday’s spacewalk, Rubins and Glover returned inside Quest at 1:16 p.m. EST after seven hours and four minutes. This marks the longest single EVA in either of their careers to date and pushes Rubins’ total to 19 hours and 50 minutes and that of Glover to 19 hours and 20 minutes.