He may be long-retired from the British Army, and his Christian name may have a different vowel at its core, but “Major Tim” Peake will pay unique tribute on Friday, 15 January, to “Starman” David Bowie, who died last weekend from cancer. Peake and his Expedition 46 crewmate, NASA astronaut Tim Kopra, were recently announced to perform U.S. EVA-35, a planned 6.5-hour spacewalk to remove and replace a failed Sequential Shunt Unit (SSU) on the International Space Station (ISS), as well as tending to several other tasks in readiness for Commercial Crew operations. Launched on 15 December, alongside Russian cosmonaut Yuri Malenchenko, it was anticipated—though unconfirmed until early January—that Kopra and Peake would execute U.S. EVA-35. As well as representing Kopra’s third career spacewalk, it will be the first time that a Union Jack has ever been seen on the sleeve of an Extravehicular Mobility Unit (EMU) suit in the vacuum of space.
The death of Bowie prompted a massive outpouring of tribute from numerous astronauts, including Chris Hadfield, who became the first Canadian citizen to command the ISS back in spring 2013 and sang his own version of “Space Oddity,” whilst floating aboard the station. Poignantly, Hadfield delivered the lyrics “Planet Earth is blue / and there’s nothing I can do” as he beheld the grandeur of our world through the multiple windows of the cupola. Almost three years later, Hadfield tweeted on Monday: “Ashes to ashes, dust to stardust. Your brilliance inspired us all. Goodbye Starman.” High above the Earth, that same day, Tim Peake added his own tribute. “Saddened to hear David Bowie has lost his battle with cancer,” he tweeted. “His music was an inspiration to many.” Added Expedition 46 Commander Scott Kelly: “Sad to learn of the death of musician @DavidBowieReal whose inspiration lives on ‘far above the world’.”
For Peake and Kopra, the taking of protein pills, the putting-on of helmets, and the commencing of countdowns is now far behind them, as they wrap up a highly successful first month aboard the sprawling, multi-national space station. In Bowie’s words, both have “really made the grade” and in the words of ISS Operations and Integration Manager Kenny Todd, speaking yesterday (Tuesday) at a press conference at the Johnson Space Center (JSC) in Houston, Texas, they have completed a significant amount of Human Research experimentation, which all new expedition crews perform in their first weeks aloft, as they seek to chronicle their physiological and psychological adaptation to microgravity.
Summarizing the successes of recent weeks, Mr. Todd noted a busy schedule of traffic to the ISS, with Orbital ATK returning its Cygnus cargo ship to flight—and marking the first berthing of a commercial vehicle at the Earth-facing (or “nadir”) port of the Unity node—as well as Russia staging the inaugural voyage of its new Progress-MS spacecraft and Expedition 46 crewmen Kelly and Kopra performing an “Unplanned EVA” on 21 December to move the stuck Mobile Transporter (MT) and secure it at Worksite 4. “We did it with about four days of notice from the time we saw the problem to the time we went out the hatch, so that was pretty remarkable in itself,” explained Mr. Todd. “The crew and entire engineering ops team did a great job in putting that plan together and executing it.”
Looking ahead, Mr. Todd remains positive that an equally busy manifest of visitors in 2016 lies ahead. Last week, a review of launch data from the maiden flight of SpaceX’s Upgraded Falcon 9—which boosted 11 Orbcomm Generation (OG)-2 satellites into low-Earth orbit on 21 December—was completed, and, according to Mr. Todd, “all indications are very positive” that ISS-bound Commercial Resupply Services (CRS) Dragon cargo missions will resume in the near future. Current plans call for the CRS-8 Dragon, which is carrying the long-awaited Bigelow Expandable Activity Module (BEAM), to be launched to the station as soon as 8 February, although precise details are expected to be hammered-out over the next couple of weeks. In the meantime, the OA-4 Cygnus was previously scheduled to unberth from Unity nadir on 25 January, but according to Mr. Todd the ISS Program may extend its stay-time “a little longer” to keep the station clean and utilize the outgoing cargo ship to stow as much trash as possible before it departs.
Moving onto plans for Friday’s EVA, he stressed that the primary objective stems from the failure—on Friday, 13 November, last year—of Power Channel 1B on the station’s S-6 segment, which is situated at the furthest-starboard point of the 356-foot-long (108.5-meter) Integrated Truss Structure (ITS). The truss houses eight sets of Solar Array Wings (SAWs), mounted on the S-6, S-4, P-6 and P-4 segments, together with their associated radiators and cooling hardware, as well as providing locations for scientific payloads, storage places for spares and positions for Canada’s 57.7-foot-long (17.6-meter) Canadarm2 robotic arm. Each SAW is equipped with a Sequential Shunt Unit (SSU), which serves to regulate power generated by the massive arrays at an established “set-point” of 160 volts, by shunting and unshunting 82 array “strings.” This ensures a steady electrical output across the space station. Although the failed Power Channel 1B was quickly recovered after November’s failure, its loss was traced to a power short within the 1B SSU, necessitating its replacement with a spare unit already aboard the ISS.
“It’s something we can live with for some period of time while we watched the vehicle traffic,” Mr. Todd told his JSC audience, but it was also important to protect the opportunity to remove and replace the 1B SSU at some point in January. Despite the having been recovered, it was decided that in the interests of preventing damage to downstream hardware, Power Channel 1B would be kept isolated, with the ISS running on its seven remaining channels, until such time as it could be re-integrated back into the grid. That said, there was a level of urgency in getting the replacement task behind them. “The reality is that if we were to have an additional failure in another channel,” said Mr. Todd, “we would probably find ourselves a little more strapped.”
Adding that there was “little doubt” that the cause of November’s failure indeed lies with the SSU, he drew parallels with a similar SSU failure in May 2014—which occurred in Power Channel 3A, located on the neighboring S-4 truss—and its subsequent replacement by Expedition 41 spacewalkers Reid Wiseman and Barry “Butch” Wilmore during U.S. EVA-28 in October 2014. In readiness for this second such Removal & Replacement (R&R) task in less than 18 months, a spare SSU was already in residence aboard the space station and was checked-out by the crew in December. In fact, Wiseman will be sitting at the Capcom’s console in the Mission Control Center (MCC) for Friday’s spacewalk, serving in the “Ground Intravehicular” (IV) role, talking the spacewalkers through their task. As for Kopra and Peake, both men trained extensively for an SSU R&R task in the Neutral Buoyancy Laboratory (NBL), as part of their generic EVA training. Since then, they have also studied video and other procedures, had tag-ups with EVA specialists on the ground, and Peake recently participated in a Virtual Reality (VR) simulation of his activities.
On Monday, 11 January, Peake tweeted to his 322,000 followers that he had completed his “final suit fit check prior to Friday’s EVA,” assisted by Scott Kelly, and stressed that his bulky ensemble “feels just great.” Kicking off Friday’s activities, Kopra and Peake will undertake 60 minutes of “pre-breathing” on masks, during which time the inner “equipment lock” of the Quest airlock will be depressed from its ambient 14.7 psi to 10.2 psi. Assisted by Kelly, who serves as “Suit IV” for the spacewalk, they will don and purge their U.S.-built Extravehicular Mobility Unit (EMU) suits and the airlock’s atmosphere will be repressurized back up to 14.7 psi. This will allow them to follow a nominal pre-breathing regime, lasting 50 minutes, followed by an additional 50 minutes of In-Suit Light Exercise (ISLE). The latter was first trialed during the third EVA of the STS-134 shuttle mission in May 2011 and serves to rapidly remove nitrogen from the spacewalkers’ bloodstreams, thereby avoiding a potentially fatal attack of the “bends” and skirting the need for the EVA crew to “camp out” overnight in Quest. At length, Kelly will oversee the transfer of Kopra, Peake and their equipment from the equipment lock into the outer “crew lock.”
Depressurization of the crew lock will then commence, pausing briefly at 5 psi for pressure and leak checks, before resuming until it achieves a condition of near-vacuum. U.S. EVA-35—the 35th EMU-based spacewalk to originate from the Quest airlock, and in the absence of the space shuttle, since February 2002—is scheduled to get underway at 7:55 a.m. EST. Kopra, designated “EV1,” with red stripes on the legs of his suit for identification, will depart the airlock first, carrying the tools for the R&R task, followed by Peake (“EV2”), who will be wearing a pure-white suit and will bring out the spare SSU itself. The duo will perform customary “buddy checks” of each other’s suits and tethers, then “temp-stow” some hardware onto the exterior of Quest.
Kopra will move to the Starboard Crew and Equipment Translation Aid (CETA) cart in order to retrieve a foot restraint, which he will later use to stabilize himself at the SSU worksite. He will connect safety tether anchors for both himself and Peake at a handrail on the S-1 truss, which lies close to the center of the ITS, then begin the steady translation out to the far end of the truss and the S-6 segment. When he arrives, he will set up the foot restraint, positioning it to give himself good access to the failed SSU, and will be joined in short order by Peake, toting the replacement unit.
The actual replacement must occur during the “night” portion of the station’s 90-minute orbit, in order to protect the spacewalkers from electrical output in the SAW. “This time pressure,” explained Lead U.S. EVA-35 Spacewalk Officer Paul Dum, “means that it’s critical that the crew is ready to step into contingency procedures quickly, if necessary.” With Peake on hand to provide visual cues and pass tools to his crewmate, Kopra will pull out the failed SSU and stow it onto his Body Restraint Tether (BRT). It is anticipated that the changeout will require around 15 minutes of the 45-minute “night” period. He will then install the spare SSU and bolt it into place, after which both men will work to bag up the failed unit and Peake will bring it back to Quest, stowing it inside the crew lock.
Returning to the airlock, and dropping off his foot restraint on the way, Kopra will head into his second task: the re-installation of the Non-Propulsive Valve (NPV) into a very tight area, close to the port-side end-cone of the Tranquility node. The valve was removed by Expedition 42 spacewalker Barry “Butch” Wilmore during U.S. EVA-30 back in February 2015, in order to provide better clearance for the Leonardo PMM relocation in May. After several months stored inside the station, the reinstallation of the NPV was expected to be performed by Kjell Lindgren during U.S. EVA-32 in October 2015, but was deferred, and only now is it being returned to its original location. Kopra will remove a cover plate, installed by Wilmore, then secure the NPV back into position with four bolts.
Other tasks include dropping off a cable on the port side of the station’s Z-1 truss—which is situated atop the Unity node—for access by Peake, later in the EVA, and removing a Launch Restraint Bracket from Pressurized Mating Adapter (PMA)-3. At present, PMA-3 resides at the port “end” of Tranquility, but it is expected to be robotically detached later in 2016 and relocated to the space-facing (or “zenith”) port of the Harmony node, where it will be outfitted with an International Docking Adapter (IDA) and serve as the backup location for Commercial Crew vehicles. Removing the Launch Restraint Bracket will allow for cables to be disconnected in the future, prior to the PMA-3 relocation. Kopra’s last scheduled task on U.S. EVA-35 will be to remove a failed light on Camera Group (CG)-9, which is situated on the station’s P-1 truss.
Meanwhile, Peake will press on with an activity that has been ongoing during several other U.S. EVAs in 2015, to lay cables in anticipation of the arrival of two IDAs for Commercial Crew operations. Returning from the SSU R&R task, he will pick up an IDA Cable Bag and translate to the nadir face of the U.S. Destiny laboratory, where he will temp-stow it and begin routing the cables. One “leg” will be routed aft, toward Unity, whilst another—the Enhanced Processor & Integration Communications (EPIC) Multiplexer-Demultiplexer (MDM)—will traverse over the zenith side of the lab, then in a portward direction. “One of the key challenges EV2 Tim Peake will face during this portion of the EVA,” said Mr. Dum, “will be the tightness of the translation path and the number of other cables that present snag hazards for him as he goes.”
Having routed the cable to the port side of the Z-1 truss, Peake will connect it to the cable left for him earlier by Kopra. He will make two connections of the EPIC MDM cable to “pigtails” of an Ethernet cable, dedicated to Russia’s long-delayed Multipurpose Laboratory Module (MLM). Peake will then retrieve a third IDA cable, which he will route forward along the length of Destiny, then zenith and forward onto Harmony, leaving it for eventual connection to IDA.
Their work completed, Kopra and Peake will return to the Quest airlock, after an excursion which is anticipated to run for about 6.5 hours. Kopra has presently accrued a career total of eight hours and 48 minutes of spacewalking time, across two EVAs—the first at the start of his Expedition 20 increment in July 2009, the second last month—and, assuming U.S. EVA-35 runs approximately to its timeline, will return inside on Friday with more than 15 hours of experience working in the vacuum of space.
For Peake, it will wrap up the first-ever spacewalk by an “official” British astronaut, sponsored by the UK Government, and as such his EMU will boast the Union Jack on its sleeve. Although Mike Foale made an EVA during shuttle mission STS-63 in February 1995 and fellow British-born NASA astronauts Piers Sellers and Nick Patrick have also completed spacewalks in their careers, all three did so in their capacity as joint-citizenship holders with U.S. nationality. As he “steps through the door” of Quest on Friday, “floats in a most peculiar way” and undoubtedly notices that “the stars look very different,” perhaps Peake will have a few fleeting seconds to reflect upon David Bowie’s iconic words. For after six years of training, the time has come for him to leave the “capsule” of the ISS.
And Tim Peake is certainly a man who dares.
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