Behnken, Cassidy Join "Pretty Exclusive Club", Both Log Tenth Spacewalks

Two NASA astronauts smoothly powered through a lengthy spacewalk on Tuesday, tending to a multitude of tasks which will expand the capabilities of the International Space Station (ISS). Expedition 63 crewmen Bob Behnken and Chris Cassidy were both embarking on the tenth EVAs of their respective careers—jointly tying an already-extant record for the greatest number of spacewalks by a U.S. citizen—and spent five hours and 29 minutes outside the sprawling orbital complex. By the time they returned back to the station’s Quest airlock, Behnken had established his new credentials as the fourth most experienced spacewalker in history, whilst Cassidy has nudged himself into the Top Ten.

Chris Cassidy now sits in ninth place on the list of the world’s most experienced spacewalkers, with over 54 EVA hours. Photo Credit: NASA

Aided by Expedition 63 crewmates Doug Hurley and Ivan Vagner, the spacewalkers suited up in the inner “equipment lock” of Quest, where they performed In-Suit Light Exercise (ISLE) tasks, prior to being sealed in the outer “crew lock”. The airlock’s outer hatch was pushed open by Behnken—serving as “EV1”, the lead spacewalker—at 7:12 a.m. EDT, about 25 minutes ahead of the timeline. Entering the vacuum of space for the tenth time in their careers, Behnken and Cassidy join U.S. spacewalking supremos Mike Lopez-Alegria and Peggy Whitson in having conducted as many as ten EVAs.

Dragon Endeavour crewmen Doug Hurley (left) and Bob Behnken trained extensively to support this summer’s quartet of EVAs. Photo Credit: NASA

After checking their suits and tethers, Behnken and Cassidy set to work. Their first task was the installation of a unique “robot hotel”, known as the Robotic Tool Stowage (RiTS), onto the station’s Mobile Base System (MBS). The RiTS provides a protective storage point for critical robotic tools. Launched last December aboard SpaceX’s CRS-19 Dragon cargo ship, it affords robotic hardware adequate protection from both the extreme heat and frigid cold of space and guards against radiation and micrometeoroid impacts. It also allows storage space inside the ISS for robotic equipment to be minimized. Having an external location to hold all robotic tools is also useful for the station’s Dextre “hand” to easily locate and grapple what it needs for its myriad tasks.

The RiTS’ first residents will be the two Robotic External Leak Locators (RELLs), launched via Cygnus resupply ships in December 2015 and in April of last year. These two robotic “sniffers” provide a means to quickly and effectively locate external ammonia leaks and rapidly confirm a successful repair. In the late summer of 2017, the first RELL identified a minor leak and took corrective action.

The flight unit of the Robotic Tool Stowage (RiTS), pictured at right, with an engineering model of the Robotic External Leak Locator (RELL) at left. Photo Credit: NASA

At one stage, veteran astronaut Mike Lopez-Alegria—currently the United States’ most seasoned spacewalker, with 67 hours and 40 minutes across ten spacewalks between October 2000 and February 2007—noted that Behnken and Cassidy were actually the first astronauts to log ten EVAs in the U.S.-built Extravehicular Mobility Unit (EMU).

Lopez-Alegria performed two of his EVAs in a Russian space suit, whilst Peggy Whitson did likewise on one of her ten EVAs. “They join @AstroPeggy and me in a pretty exclusive club of 10-EVA-ers,” tweeted Lopez-Alegria, “but they’re the first to do them all in the NASA EMU.”

Mike Lopez-Alegria, pictured here during an EVA in 2007, is presently the United States’ most experienced spacewalkers and the first American to log as many as ten spacewalks. Photo Credit: NASA

With the RiTS work done, they pressed on with their next tasks. After having encountered some difficulty during an initial attempt on 1 July, Behnken and Cassidy successfully removed handling aids (known as “H-fixtures”) from two locations at the base of the solar arrays. The H-fixtures were used during ground processing of the massive arrays before launch and must now be removed to prepare for future upgrades to the ISS power infrastructure. For an ex-Navy SEAL, skilled in underwater demolition, it was perhaps unsurprising that Cassidy was put to work on this decidedly over-water “demolition” task, jamming pliers into the H-fixture mechanism, then working it loose.

The two men then returned to Quest to re-set their safety tethers and moved to the Tranquility node on the port side of the station. Here they were tasked with preparing the node’s exterior for the arrival of NanoRacks’ Bishop commercial airlock, scheduled to ride aboard SpaceX’s first CRS2 Dragon cargo ship in the fall. They worked to “tie-back” three axial shields set up on Tranquility’s port-side Common Berthing Mechanism (CBM) in March 2017 by Expedition 50 spacewalkers Shane Kimbrough and Peggy Whitson. During that EVA, it was intended that four shields should be fitted to protect the CBM from micrometeoroid impacts. However, one of the shields inadvertently slipped from Kimbrough’s gloved hands and was lost. As such, the spacewalkers had to fit only three shields to the four “quadrants” around the port-side CBM, leaving one quadrant exposed to the space elements.

Bob Behnken is now the fourth most experienced spacewalker in the world, with over 61 hours of EVA to his credit. Photo Credit: NASA

Today, more than three years later, it was the task of Behnken and Cassidy to tie-back those axial shields to prepare for the next arrival at Tranquility’s port CBM. They also took time to inspect the CBM for any debris which might prevent a good seal with Bishop upon its arrival. The only issue of note seemed to be the presence of some metallic material, which they cleaned away with a tape scraper.

As previously detailed by AmericaSpace, the Bishop airlock represents a collaborative effort involving NanoRacks, Thales Alenia Space, NASA and Boeing. Plans to build it as the first-ever privately-financed airlock for the ISS were announced two years ago, via Space Act Agreement. Boeing has fabricated a passive CBM for the new airlock, capable of releasing small CubeSats and other deployable payloads.

The space station’s Dextre “hand” grapples the RELL during operations in 2017. Photo Credit: NASA

With their work at Tranquility done, the astronauts wrapped up their spacewalk by routing a pair of ethernet cables and Behnken replaced a lens filter on an external camera. They returned to Quest to conclude an EVA lasting five hours and 29 minutes. And when one stacks up the numbers, this puts Behnken—with a cumulative total of 61 hours and ten minutes—in fourth place on the list of the world’s most experienced spacewalkers, behind Russia’s Anatoli Solovyov and fellow U.S. astronauts Mike Lopez-Alegria and Drew Feustel. Cassidy, with 54 hours and 51 minutes, edges himself into ninth place on the list.

It is a peculiar anomaly to see such a gap between them, in view of their broad equivalence of experience, but one should recall that—like so many other things in life—not all EVAs are created equal. Behnken’s past spacewalks have all lasted around six hours or longer; today’s EVA, in fact, was the shortest in his career so far. Cassidy has also logged a few heavy-duty spacewalks in terms of duration, although a planned 6.5-hour EVA in July 2013 was curtailed after just 90 minutes when his crewmate Luca Parmitano experienced potentially life-threatening water intrusion into his helmet.  

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