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Expedition 55 Flight Engineers Drew Feustel and Ricky Arnold of NASA completed the fifth spacewalk of this year at 2:10 p.m. EDT, lasting 6 hours, 31 minutes. The two astronauts moved the Pump Flow Control Subassembly (PFCS) from a spare parts platform on the station’s truss to the Dextre robotic arm. The PFCS drives and controls the flow of ammonia through the exterior portions of the station’s cooling system. The team then removed and replaced a camera group and a degraded Space to Ground Transmitter Receiver Controller, and was also able to complete several get-ahead tasks.

Spacewalkers have now spent a total of 54 days, 16 hours and 40 minutes working outside the station in support of assembly and maintenance of the orbiting laboratory.

For more information about the International Space Station, visit www.nasa.gov/station.

Expedition 55 Flight Engineers Drew Feustel and Ricky Arnold of NASA switched their spacesuits to battery power at 8:39 a.m. EDT, signifying the official start of today’s planned six-and-a-half-hour spacewalk outside the International Space Station.

Watch the spacewalk live on NASA Television and the agency’s website.

Feustel is wearing the suit bearing the red stripes, and Arnold’s suit has no stripes. Views from a camera on Feustel’s helmet are designated with the number 17, and Arnold’s is labeled with the number 18. Feustel is designated extravehicular crew member 1 (EV1) for this spacewalk, the eighth of his career. Arnold, embarking on his fourth spacewalk, is extravehicular crew member 2 (EV2).

NASA Television has begun coverage of today’s spacewalk, as Expedition 55 Flight Engineers Drew Feustel and Ricky Arnold of NASA work outside the International Space Station for approximately 6.5 hours. The spacewalk is scheduled to begin at 8:10 a.m. EDT.

The objective of today’s spacewalk will be to move a component called a Pump Flow Control Subassembly (PFCS) from a spare parts platform on the station’s truss “backbone” to the Special Purpose Dexterous Manipulator (Dextre) robotic arm. The PFCS drives and controls the flow of ammonia through the exterior portions of the station’s cooling system. Robotics controllers on Earth will use Canadarm2 and Dextre to perform final installation on the port-side truss for checkout.

Follow along on NASA Television and the agency’s website. Keep up with station and crew activities via Twitter @space_station.

The Expedition 55 crew on board the International Space Station has been working hard to prepare for Wednesday’s spacewalk, and they’ll still have a lot of difficult work ahead of them when Flight Engineers Ricky Arnold and Drew Feustel head outside the airlock. If you’ve ever wondered what makes spacewalks such a big deal, check out chapter 17 of the new NASA ebook, The International Space Station: Operating an Outpost in the New Frontier. The book, which was written by space station flight directors, is now available to download for free at… https://go.usa.gov/xQbvH.

Chapter 17: Extravehicular Activities – Building a Space Station
Planning and Training Extravehicular Activity Tasks

On paper, the tasks needed for International Space Station assembly—e.g., driving a bolt, carrying something from one place to another, taking off a cover, plugging in an electrical cord—might not seem too complex. However, conducting such tasks while wearing a spacesuit with pressurized gloves (possibly with one’s feet planted on the end of a long robotic arm), working in microgravity, maneuvering around huge structures while moving massive objects, having time constraints based on spacesuit consumables, and using specialized equipment and tools made these tasks and EVAs challenging.

Tasks such as working with cables or fluid hoses are hand-intensive work—fingers and forearms get quite a workout in pressurized gloves that feel like stiff balloons and resemble oversized garden gloves. Added to these complexities, space “walking” is mostly done with the hands. The astronaut grasps handholds and maneuvers the combination of the Extravehicular Mobility Unity, Simplified Aid for EVA Rescue, tools, and himself or herself around the structure.

The team on the ground has to come up with a choreography and order of events for the EVA, in advance. The flight control team creates the EVA timelines based on a high-level prioritized list of tasks determined by ISS management (e.g., move a specific antenna, install a particular avionics box). The flight controllers start with the top ISS priority task and assesses the other tasks that can fit into the EVA based on multiple factors such as how long the tasks will take based on past experiences, whether both crew members need to work together, task location on the ISS, how much equipment will fit into the airlock, the tools required, crew experience level, and the level of crew effort to complete the task. A task that might fit (but only if the team is efficient) is put on the list as a “get-ahead” task.

Real-time discussions in Mission Control of EVA time remaining, crew fatigue, and suit consumables could allow the get-ahead task to be accomplished in addition to the planned tasks. Some tasks are performed on a “clock”; i.e., if power is removed from an item, it might get cold and need heater power in a matter of hours or sometimes within minutes to prevent damage. While a timeline is still in a draft version, the team conducts testing as required to prove out the operations. The team then trains the crew and refines and/or changes the timeline, sometimes up to the day of the EVA.

Keep reading at https://go.usa.gov/xQbvH.

Two NASA astronauts are finalizing their preparations ahead of Wednesday morning’s spacewalk to swap thermal control gear outside the International Space Station. The Expedition 55 crew also worked on biomedical operations, radiation checks and Cygnus communications gear.

Flight Engineers Ricky Arnold and Drew Feustel checked their tools and reviewed their procedures one last time today before tomorrow’s spacewalk. The pair will work for about 6.5 hours swapping a pair of thermal control devices, known as Pump Flow Control Subassemblies, which control the circulation of ammonia keeping external station systems cool.

The veteran spacewalkers will set their spacesuit batteries to internal power Wednesday at about 8:10 a.m. EDT signaling the official start of the 210^th spacewalk in space station history. NASA TV will begin its live broadcast of the activities beginning at 6:30 a.m.

Science and maintenance are always ongoing aboard the orbital lab even despite the spacewalk and cargo mission readiness activities. Feustel and Japanese astronaut Norishige Kanai collected their biological samples this morning and stowed them in a science freezer for later analysis. Cosmonaut Oleg Artemyev explored cardiac bioelectric activity at rest. Commander Anton Shkaplerov collected radiation measurements from dosimeters he retrieved from the orbital lab’s U.S. segment.

Orbital ATK is getting its Cygnus space freighter ready for launch Sunday at 5:04 a.m. to deliver science, supplies and hardware to the Expedition 55 crew. Astronaut Scott Tingle checked out command and communications gear that will be used when Cygnus arrives four days later on Thursday for capture at 5:20 a.m.