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Cosmonauts conduct VKD-47 spacewalk
A pair of Russian cosmonauts spent unbder seven hours outside the International Space Station, ISS, on November 18, 2o20. Sergei Ryzhikov and Sergei Kyd-Sverchkov from the Soyuz MS-17 crew performed the 47th Russian spacewalk, VKD-47, in the history of the ISS project. Their primary goal was to lay the groundwork for the addition of the MLM Nauka module to the Russian Segment in 2021.
VKD-47 spacewalk at a glance:
During VKD-47 spacewalk, the cosmonauts used the Poisk module, MIM2, as their vestibule for the first time instead of the veteran Pirs Docking Compartment, SO1, which has served as an airlock for Russian spacewalkers since its launch in 2001. The 19-year-old module was slated to be discarded from the station in 2021, immediately after the launch of the Nauka module and all subsequent Russian spacewalks were to be staged from the remaining Poisk module. Although it was identical to the retiring Pirs, Poisk was launched more than eight years later (in 2009) and was attached to the opposite (sky-facing) docking port on the transfer compartment of the Zvezda Service Module, SM.
Ryzhikov and Kud-Sverchkov, who were venturing outside for the first time in their careers, were wearing Orlan-MKS spacesuits designated No. 5 and No. 4. For the purposes of identification, the No. 4 suit worn by Ryzhikov had red vertical stripes and Kud-Sverchkov's suit was emblazoned with blue lines.
The main task of the sortie was to confirm that the egress hatch of the Poisk module could be safely opened and closed without developing any leaks. (Prior to the VKD-47 spacewalk, the hatch of the Poisk module had never been opened in orbit.) The cosmonauts were to inspect o-rings providing pressurized seal between the hatch and the hull of the module and had an option to replace it if necessary with one of two spare o-rings available to them.
The initial hatch opening was scheduled for 17:30 Moscow Time (9:30 a.m. EST) on November 18. The cosmonauts were then expected to close the hatch and re-pressurize the module up to 260 millimeters on the mercury table.
If all the leak checks in the Poisk module confirmed a reliable seal, the cosmonauts were expected to re-open the hatch and exit the station. Their first task was to replace an aging fluid flow regulator No. 1, SP RRZh (Smennaya Panel Regulyatora Raskhoda Zhidkosti), within the thermal control system of the Zarya FGB module. The flow regulator No. 1 on the Zarya had already been replaced in 2004 during the VKD-11 spacewalk, followed by the replacement of regulator No. 2 in 2013 during the VKD-33 spacewalk. For safety reasons, the new flow regulator and the replacement units were to be carried to the work area and back in a pressurized container.
Next, the cosmonauts had to remove an assembly with the SNP407 connectors from the exterior of the station.
Next, the cosmonauts were scheduled to rewire the cables of the Transit-B telemetry system from the retiring Pirs to Poisk. Also, the cosmonauts were to clean window No. 8 on the Zvezda Service Module, SM. Finally, the cosmonauts had to re-orient BKDO instrument mounted on the Poisk module that was used to measure residue from thruster firings.
These primary tasks of the spacewalk were expected to take 5 hours and 33 minutes.
"Get ahead" tasks
If the cosmonauts fulfilled main goals of their spacewalk on time and without problems, the pair also had a list of "get-ahead" tasks for which planners allocated an additional hour and 35 minutes.
For the purposes of Impakt experiment, the cosmonauts had to retrieve Pallet No. 1 which measures the influence of engine burns on the Zvezda's aggregate compartment and place Pallet No. 2 in its place.
According to Roskosmos, the Impakt experiments aimed to help in the development of a functional model for the dissipation of the exhaust stream during the firing of the station's thrusters. This methodology might be used to forecast the level of contamination of various payloads and service equipment on the exterior of the station, so it would be possible to know the level of degradation of components and their toxicity in cases when the equipment has to be brought back into the pressurized compartments of the station.
Also, cosmonauts could photograph surfaces of the GZU DO+T and DO+K sensors.
VKD-47 spacewalk statistics (according to NASA):
According to NASA, the elapsed time of the VKD-47 was to be measured from the first opening of the hatch until the second closure of the hatch at the end of the spacewalk. The clock would not be stopped during the partial repressurization of the Poisk module with hatches closed. However, Roskosmos sources implied that the spacewalk time would be counted from the moment when the hatch would be opened for the second time.
On November 18, 2020, Sergei Ryzhikov and Sergei Kud-Sverchkov entered the Poisk module and began pre-breathing oxygen around one hour before planned start of the spacewalk. The initial controlled drop of pressure in the module was reported around 16:47 Moscow Time (8:47 a.m. EST). By 16:50 Moscow Time, the pressure was reduced to 550 millimeters, according to NASA. A 10-minute stabilization period was completed around 17:00 Moscow Time (9 a.m. EST). By that time, cosmonauts reported pressure at 577 millimeters. The mission control then initiated another five-minute pressure check test.
In the meantime, by 17:10 Moscow Time (9:10 a.m. EST), Kate Rubins closed the hatch from the PGO compartment of the Zarya FGB module to the Zvezda Service Module, SM. She still had a direct access to the Soyuz MS-17 spacecraft docked at the MIM1 Rassvet module, itself attached to a nadir port on Zarya's PGO.
The cosmonauts reported that they completed their oxygen pre-breath around 17:44 Moscow Time (9:44 a.m. EST) and were ready to begin the depressurization of the Poisk module, which started immediately. The pressure inside Poisk approached vacuum around 18:00 Moscow Time (10 a.m. EST) and the cosmonauts began preparations for opening the hatch. Cosmonauts reported some spring-loaded action as they opened the hatch at 18:12:28 Moscow Time (10:12 a.m. EST) and two pieces of debris were seen separating from the hatch area on the exterior of Poisk. After the inspection of the seal by the cosmonauts, who found no problems, mission control directed the crew to close the hatch at 18:18 Moscow Time (10:18 a.m. EST).
By 18:27 Moscow Time, the pressure inside Poisk was increased to 264 millimeters, allowing mission control to begin leak checks. Then, the second depressurization of the module started around 18:40 Moscow Time (10:40 a.m. EST). Around 18:49 Moscow Time (10:49 a.m. EST), mission control directed spacewalkers to switch their spacesuits to autonomous power. The hatch was re-opened around 18:55 Moscow Time. The cosmonauts then installed a protective ring on its interface and reported the hatch fully secured at 19:05 Moscow Time.
Spacewalk begins with failed attempt to replace a fluid flow regulator
Cosmonauts transfer to the Zarya module with a pressurized container holding a fluid flow regulator at the beginning of the spacewalk.
Sergei Kud-Sverchkov exited Poisk at 19:07 Moscow Time (11:07 a.m. EST), as the ISS was flying over the Pacific Ocean. Ruzhikov followed him around 19:16 Moscow Time. The container with a fluid flow regulator was extracted from Poisk around 19:14 Moscow Time and around five minutes later, the cosmonauts told mission control that they had been ready for a translation to the Zarya.
The cosmonaut began disconnecting the old regulator at around 20:00 Moscow Time (12 p.m. EST). The first attempt to open the pressurized container was made at 20:10 Moscow Time (12:10 p.m. EST) but it would not open. Mission control directed cosmonauts to check 12 bolts on the perimeter of the cover. After some consultations on the ground and a rest period for the crew, at 20:25 Moscow Time (12:25 p.m. EST) mission control recommended cosmonauts to use a wrench to move the handles of the stuck bolt, however cosmonauts reported that the method would not work. Mission control then instructed the crew to put the old flow regulator back into its place on the Zarya module and return back to Poisk with the unopened container and the new flow regulator inside.
At 12:45 p.m. EST, mission control instructed the crew to remove the container from its stowage position and return it to the Poisk module.
The cosmonauts made it back to the Poisk around 21:00 Moscow Time (1 p.m. EST). Ryzhikov reentered the module around 21:10 Moscow Time and Kud-Sverchkov then pushed the container inside Poisk three minutes later.
Re-routing Transit-B cables
By 21:30 Moscow Time (1:30 p.m. EST), the cosmonauts were busy working with the Transit-B telemetry cable. By 22:20 Moscow Time (2:20 p.m. EST), the cosmonauts reported that the cables had been connected to the Poisk at the KhFP 7-2 interface. Mission control then asked cosmonauts to photograph the connecting plate and then transition to other tasks. By that time, the crew was around one hour behind its VKD-47 schedule.
At 22:30 Moscow Time (2:30 p.m. EST) mission control instructed the crew to move to the aggregate compartment of the Zvezda Service Module, SM, but before the cosmonauts could do that they were given a short break around 22:40 Moscow Time. Mission control also said that the window-cleaning operation was dropped from the tasks of the VKD-47 spacewalk. On the Zvezda, the cosmonauts were still expected to remove "witness plates" from the Impakt experiment.
The cosmonauts began the transfer to the Zvezda around 22:45 Moscow Time (2:45 p.m. EST). They reached the aggregate compartment just before 23:00 Moscow Time. Around that time, apparently in response to the cosmonauts' suggestion that they were near the area where a hypothetical impact could cause an air leak from Zvezda's PrK compartment (Insider Content), mission control gave spacewalkers a (previously unplanned) task of photographing the suspected site (only 5 minutes was allocated for that work). Navigating the spacewalkers, mission controllers advised the cosmonauts to look near the exhaust deflector (GZU) on Plane 4 of the service module and near the first letter "Z" in the Zvezda inscription on the body of the module. However, Ryzhikov responded that he saw nothing suspicious in the area, essentially putting to rest the cosmonauts' hypothesis about the external impact.
The cosmonauts then began removing Impakt experiment trays No. 1 and No. 2, around 23:10 Moscow Time (3:10 p.m. EST), first securing them to the tethers and putting on protective covers. More than five hours into their spacewalk, cosmonauts struggled fixing the new tray onto the railing. It was finally installed just before 23:30 Moscow Time (3:30 p.m. EST).
Around 10 minutes later, mission control advised the crew to eject the cleaning towels into space and, after a short break, be ready for the transfer back to Poisk. Initially, flight managers told crew members to throw away a glass cover from the newly installed Impakt experiment along with the towels, but then instructed the crew to pack the cover and bring it back inside the station.
Around 23:45 Moscow Time, the cosmonauts inspected each other's spacesuits for contamination and cleaned suspected areas on the suits and hardware before their jettisoning. Mission control advised the crew to wait for an orbital sunrise to have better lighting for cleaning operations and safe jettisoning of the towels at 23:55 Moscow Time (3:55 p.m. EST). The cosmonauts then had to take another short break, while mission controllers were rotating solar panels on the Zvezda 90 degrees (with their photo-elements toward Plane I), to open a safe passage for the spacewalkers.
Spacewalkers reported seeing solar panels in correct position for the transfer at 00:03 Moscow Time (4:03 p.m. EST). The cosmonauts then moved for the repositioning of the thruster plume impingement monitor on the Zvezda.
At 00:15 Moscow Time (4:15 p.m. EST), mission control asked cosmonauts to activate their GoPro cameras and leave them on for the rest of the spacewalk.
At 00:24 Moscow Time, mission control instructed cosmonauts to approach the hatch on Poisk and begin reentry after the inventory of all their tools. The inventory was made around 00:30 Moscow Time (4:30 p.m. EST). Sergei Ryzhikov was seen reentering the hatch around 00:33 Moscow Time, followed by Kud-Sverchkov at 00:45 Moscow Time (4:45 p.m. EST). Around 00:50, mission control gave the go ahead to cosmonauts to remove the protective ring from the hatch. Cosmonauts confirmed the removal of the ring around 00:55 Moscow Time (4:55 p.m. EST).
After a 10-minute period for the drying of the sublimation hardware in the spacesuit, the hatch into the Poisk module was closed at 01:01 Moscow Time (5:01 p.m. EST) and the re-pressurization process started around 01:05 Moscow Time (5:05 p.m. EST). According to the Russian mission control, the VKD-47 spacewalk lasted 6 hours 47 minutes and 6 hours 48 minutes, according to NASA.
Preliminary planned timeline of the VKD-47 spacewalk, according to Roskosmos:
"Get ahead" tasks: