Three U.S. astronauts will venture outside the International Space Station (ISS) over the next two weeks to undertake a series of maintenance tasks on the exterior of the orbiting outpost. Expedition 53 Commander Randy Bresnik and Flight Engineer Joe Acaba, both of whom have two previous sessions of Extravehicular Activity (EVA) under their belts, and first-time spacewalker, Flight Engineer Mark Vande Hei, will replace and lubricate one of two Latching End Effectors (LEE) on the 57.7-foot-long (17.6-meter) Canadarm2 and replace cameras at a pair of locations on the station’s expansive Integrated Truss Structure (ITS). Outlined in a media briefing at the Johnson Space Center (JSC) in Houston, Texas, earlier today (Monday, 2 October), the current plan will see Bresnik and Vande Hei perform two EVAs on 5 and 10 October, with Bresnik joined by Acaba for the third spacewalk on the 18th.
For Bresnik, who launched to the ISS aboard Soyuz MS-05 in late July, this represents the third EVA of his career. He previously logged 11 hours and 50 minutes of spacewalking time during shuttle Atlantis’ STS-129 mission in November 2009, during which he installed equipment onto the European Columbus lab, to the station’s truss and to the Quest airlock. Acaba, meanwhile, totaled 12 hours and 57 minutes of time in the vacuum of space, back in March 2009, during Discovery’s STS-119 flight. During his EVAs, Acaba worked to install the S-6 truss component, together with an antenna onto Japan’s Kibo lab and a Crew and Equipment Translation Aid (CETA) cart.
This trio of spacewalks will bring to ten the total number of ISS-based EVAs to have taken place since January, the greatest in a single calendar year since 2013. This includes one spacewalk in Russian suits and nine in U.S.-built Extravehicular Mobility Units (EMUs). Since the end of the shuttle era, all ISS spacewalks have originated from the station itself, with U.S. excursions beginning and ending at the Quest airlock. The trio of spacewalks by Bresnik, Vande Hei and Acaba represent the 44th, 45th and 46th “Stage” EVAs performed in the absence of a resident Space Shuttle since February 2002. Significantly, nine is the greatest number of U.S. Stage EVAs ever performed in a single calendar year, eclipsing the previous record of eight, set in 2007 during a period of major ISS construction, which featured the arrival of new truss segments and the Harmony node.
In fact, 2017 has been a dramatic year, not only for EVAs, but for EVA records. On 6 January, Peggy Whitson became the world’s oldest spacewalker, aged 56. It was a record that she would set on three more occasions in March and May, as well as becoming the holder of the largest number of EVAs—and the greatest number of spacewalking hours—by a woman. During Expedition 51, she and Jack Fischer also performed the 200th spacewalk in support of ISS construction and maintenance. During the course of 2017’s EVAs, astronauts and cosmonauts from the United States, Russia and France have installed new lithium-ion batteries, configured Pressurized Mating Adapter (PMA)-3 at the space-facing (or “zenith”) port of the Harmony node for Commercial Crew operations and attended to other tasks.
Last week, Bresnik and Vande Hei spent time in the Quest airlock, resizing their suits for the spacewalks. The duo also checked out the Simplified Aid for EVA Rescue (SAFER) backpacks, as well as their tethers and tools. They also scrubbed the suits’ coolant loops and filled them with water, continuing their EVA preparations over the weekend. During all three EVAs, Bresnik—designated EV1, with red stripes on the legs of his suit for identification—will wear EMU No. 3003. Meanwhile, Vande Hei will wear EMU No. 3008 for the first two spacewalks and Acaba will wear it for the third.
Both suits have an exceptionally long service history, both within the Space Shuttle Program (SSP) and throughout the ISS era. EMU No. 3003 was first flown on STS-77 in May 1996, but both it and EMU No. 3008 saw their first actual service on STS-82, the second Hubble Space Telescope (HST) servicing mission in February 1997. The two suits played an integral role in the gradual “internationalization” of the shuttle, when 3008 was worn by Russian cosmonaut Vladimir Titov during STS-86 in October 1997 and 3003 by Japan’s Takao Doi for his nation’s premier spacewalk a month later on STS-87. These two missions marked the first occasions that non-U.S. citizens had performed EVAs in U.S.-built suits. The suits flew together on another Hubble mission, STS-103 in December 1999, and 3003 was worn by Susan Helms in March 2001 for what still stands as the longest single EVA ever undertaken in human history.
Kicking off Monday’s briefing was ISS Operations Integration Manager Kenny Todd, who outlined an exceptionally smooth month of September, beginning with the departure of Fyodor Yurchikhin, Jack Fischer and Peggy Whitson and ending with the successful departure and splashdown of SpaceX’s CRS-12 Dragon cargo ship and the arrival of Soyuz MS-06. However, Mr. Todd stressed that one of the two Latching End Effectors (LEE) on the 57.7-foot-long (17.6-meter) Canadarm2 robotic arm had experienced a stall of its motorized latches on 22 August. Canadarm2 has end-effectors on each “end”—designated “LEE-A” and “LEE-B”—which allows the arm to “inchworm” its way along the length of the Integrated Truss Structure (ITS) to reach worksites.
During the first spacewalk, which is due to begin at 8:05 a.m. EDT Thursday, 5 October, Bresnik and Vande Hei will remove LEE-A and replace it with a spare end effector, currently located on the station’s Mobile Transporter. Also on the panel for today’s news conference was Tim Braithwaite, ISS Program Liaison for the Canadian Space Agency, who noted that these LEE issues represent “expected wear and tear”, since the mechanisms are currently operating well beyond their original lifetimes. Canadarm2 was launched in April 2001, with the expectation that it would last for the station’s entire lifetime, “with maintenance”, and an anticipated functionality of between ten and 15 years. With a hint of understatement, Mr. Braithwaite stressed that CSA was “very pleased” that both LEEs have endured as long as they have—more than 16 years—before the need for maintenance.
With the satisfactory replacement of LEE-A, the second and third EVAs on 10 October and 18 October will see Bresnik, Vande Hei and Acaba lubricating the newly installed end-effector and replacing cameras on the ITS. Mr. Todd described these tasks, rather nonchalantly, as a “cats-and-dogs” category of mixed objectives. Monitoring the spacewalkers from the ground at the Capcom’s console in the Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas, during each EVA, will be NASA astronauts Mike Hopkins, Kate Rubins and Nicole Mann.