Two astronauts, including Italy’s first spacewalker, ventured outside the International Space Station today on the first of two planned EVAs from the U.S. Operating Segment (USOS) during Expedition 36. Chris Cassidy (EV1, with red stripes on the legs of his space suit for identification) and Luca Parmitano (EV2, in a pure-white suit) spent six hours and seven minutes outside on the 22nd U.S. station-based EVA. The men replaced a failed component on one of two space-to-ground antennas, installed a pair of radiator grapple bars onto the outboard P-1 and S-1 trusses, retrieved two materials science experiments, and tended to a number of “get-ahead” tasks. They remained about 30 minutes ahead of the timeline throughout the EVA, which stands them in good stead for EVA-23, which is presently scheduled to take place Tuesday, 16 July.
As described in yesterday’s AmericaSpace preview article, this is the latest spacewalk in a “hot EVA summer” for Expedition 36, which recently saw cosmonauts Fyodor Yurchikhin and Aleksandr Misurkin working outside the station’s Russian Operating Segment (ROS) on 24 June. Today’s EVA marked the 22nd time that USOS crew members have ventured outside the station’s Quest airlock, without the shuttle present, since an inaugural walk by Expedition 4 astronauts Carl Walz and Dan Bursch way back in February 2002. In addition to their key tasks, Cassidy and Parmitano performed a number of activities to prepare for the arrival of Russia’s long-delayed Nauka module, sometime early in 2014. Preparations for today’s EVA have consumed the Expedition 36 crew for some time. Last week, the spacewalkers performed standard “fit checks” of their suits inside the station’s two-part Quest airlock. They were joined by crewmate Karen Nyberg, who was at the controls of the 57-foot-long Canadarm2 from within the station’s Destiny Laboratory Module.
Early this morning, after post-sleep and personal hygiene, Cassidy and Parmitano jumped into a well-trodden path of 60 minutes spent “pre-breathing” on masks, during which time the Quest airlock’s inner “equipment lock” was depressed from its “ambient” 14.7 psi down to 10.2 psi. Their next step was to begin the process of donning and purging their bulky Extravehicular Mobility Units (EMUs)—with Parmitano’s suit emblazoned with the red, white, and green stripes of the Italian national flag—after which the atmosphere was repressurized to 14.7 psi. The astronauts then entered a nominal pre-breathing period, lasting about 50 minutes, followed by a further 50 minutes of In-Suit Light Exercise (ISLE). This protocol was first debuted on the STS-134 Shuttle mission in May 2011 and involved Cassidy and Parmitano flexing their knees for four minutes, resting for one minute, and repeating over and over until the 50 minutes were through. ISLE serves to remove nitrogen from the spacewalkers’ blood in a much shorter time period.
By 7:19 a.m. EDT, a little under an hour before the EVA was due to start, the fully-suited pair and their equipment transferred into Quest’s outer “crew lock” and Nyberg confirmed to Mission Control that the hatches between the two locks had been closed. Shortly afterwards, a “Go” was given to begin depressurization. This was interrupted, as planned, by a brief pause at 5 psi for standard leak checks, after which the process resumed and the crew lock was reduced to vacuum for an EVA start time of 8:02 a.m. EDT—about eight minutes ahead of schedule. The spacewalk officially began when Cassidy and Parmitano transferred their suits’ life-support utilities to internal battery power.
Opening the outer hatch of the crew lock, Cassidy pushed his helmeted head into the void for the second time on his current mission. He previously led a contingency spacewalk with Expedition 35’s Tom Marshburn, back on 11 May, to identify and resolve an ammonia leak from the P-6 truss. Cassidy also performed three EVAs to install and outfit Japan’s Exposed Facility on the STS-127 mission in July 2009. For Parmitano, today’s spacewalk was his first experience of EVA, and television viewers glimpsed for the first time the red, white, and green stripes of the Italian flag on the arm of a spacewalker. The astronauts’ helmets were also equipped with lights and cameras to enable terrestrial observers to follow their every move.
Upon leaving the airlock, the two men spent little time admiring their surroundings and quickly split up to attend to their respective first tasks. Cassidy moved to the Z-1 truss with a replacement Space-to-Ground Transmitter Receiver Controller (SGTRC), part of the Space-to-Ground Antenna (SGANT) hardware which funnels data between the station and Mission Control through NASA’s Tracking and Data Relay Satellite network. There are two SGANTs aboard the ISS, one of which suffered a failure of its SGTRC in December 2012 and was effectively put out of action. This left the station in a “non-fault-tolerant position,” which is highly undesirable because a single failure could cause significant problems. Despite encountering difficulties with the settings of his Power Grip Tool and the torquing of bolts, Cassidy successfully swapped out the SGTRC and transferred the faulty unit back to Quest within the first hour of the EVA. At around 9:30 a.m., NASA reported that heaters on the replacement SGTRC had been activated in readiness for checkout.
Parmitano, meanwhile, translated over the ExPRESS Logistics Carrier (ELC)-2 on the starboard S-3 truss to begin the retrieval of two scientific experiments: the Materials International Space Station Experiment (MISSE)-8 and the Optical Reflector Materials Experiment (ORMatE)-III. They form the latest in a line of payloads to expose new and affordable materials and computing elements to the ultra-vacuum, unfiltered sunlight, swinging temperature extremes, and harsh atomic oxygen environment of low-Earth orbit. MISSE-8 was launched aboard STS-134 in May 2011 and ORMatE-III followed aboard STS-135—the final flight of the space shuttle program—in July. They are housed within a suitcase-like Passive Experiment Container (PEC) and will return to Earth aboard SpaceX’s CRS-3 Dragon cargo ship in December 2013.
Upon reaching ELC-2, Parmitano photographed the experiments and removed them for transfer back to Quest. By 9:15 a.m., he had stowed both MISSE-8 and ORMatE-III inside Quest, alongside the failed SGTRC, and the two spacewalkers turned to their next critical task: the removal and installation of two Radiator Grapple Bars (RGBs) on the outboard S-1 and P-1 trusses. The bars were delivered to the ISS aboard SpaceX’s CRS-2 Dragon cargo ship in March, and their purpose is to provide the capability for Canadarm2 to interface with the station’s radiator elements, should the need ever arise to repair or replace them.
To get the work started, Parmitano installed an articulating portable foot restraint onto the end of Canadarm2 and Nyberg—operating from the robotic work station inside Destiny—“flew” him over to the bars’ location on the Mobile Base System (MBS). By 10:15 a.m., Parmitano had reached the first of the two bars and Cassidy released its hold-down bolts. Nyberg then “flew” Parmitano and the RGB for 15 minutes over to the S-1 truss for installation. Working with impressive pace—and with his eye keenly focused on the timeline—Cassidy held the RGB in position as Parmitano configured his Power Grip Tool and secured its two bolts. The first of the grapple bars was now in place on the S-1 truss.
Their next step was the retrieval of the Mast Camera—properly known as the Camera/Light Pan/Tilt Assembly (CLPA)—on the MBS, which Cassidy had begun earlier in the EVA by installing a handling fixture (or “scoop”). At 11:00 a.m., about three hours into the spacewalk, Parmitano physically removed the CLPA. It will be returned to Earth aboard the CRS-3 Dragon ship in December. As the minutes ticked away, they remained a full half-hour ahead of schedule, but dived with gusto into the next task of installing the second RGB. By 11:45 a.m., it had been removed from the MBS, transferred to the P-1 truss, and Cassidy bolted it into position with precision and perfection.
The remainder of the EVA saw Cassidy busily working to fit a pair of “jumper cables” onto the Z-1 truss. This area is filled with electrical boxes, cables, and jumpers fitted through the space station’s life. It has been nicknamed “the rat’s nest.” Despite noting the stiffness of the cables, the astronaut office’s “Iron Man”—a former U.S. Navy SEAL—ultimately had no issues with the time-consuming procedure. As Cassidy labored, Parmitano headed off to install a protective cover over Pressurized Mating Adaptor (PMA)-2, which is situated at the forward end of the Harmony node. It was last used to support the STS-135 docking in July 2011 and is expected to be used by future Commercial Crew vehicles, but the risks posed by solar radiation, micrometeoroids, and orbital debris are such that the cover will prolong its useful life. Although the installation was timelined as a two-man job, Parmitano completed it alone, securing the cover with Velcro straps.
Still working way ahead of schedule, the spacewalkers turned to their “get-ahead” tasks. Cassidy inspected the Power and Data Grapple Fixture (PDGF) on the Russian Zarya module—the station’s oldest component, launched back in November 1998—which it was thought may have had a protruding grounding wire. He saw no evidence of such a wire and extensively photographed the area, then moved on to route an 1153 data cable from the USOS to Zarya’s PDGF to eventually link it with the station’s data network. Meanwhile, Parmitano worked with storage bags, and by 1:58 p.m. the process of bringing the two spacewalkers back inside Quest had begun. The airlock’s outer thermal cover was closed and sealed at 2:00 p.m.—with Parmitano offering thanks in his native language—and EVA-22 officially concluded at 2:09 p.m. when their suits transferred to station power.
Today’s EVA—the 170th devoted to ISS construction and maintenance—has left Cassidy with a career spacewalking total of 29 hours and 42 minutes, spread across five EVAs. As the first Italian spacewalker, Parmitano joins a select group of nations, which to date includes Russia, the United States, France, Germany, Japan, Switzerland, Canada, Sweden, and China. Cassidy and Parmitano can look forward to their second spacewalk on Tuesday 16 July. On that occasion, the pair will also depart Quest at 8:10 a.m. EDT and will also spend 6.5 hours outside. USOS EVA-23 will continue the work of its predecessor. According to NASA’s Expedition 36 press kit, the EVA will involve the routing of networking cables for the Nauka module and the removal of insulation from one of the space station’s Main Bus Switching Units. A number of other activities, including “get-ahead” tasks, are also planned.
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