Readying Prichal for launch

On July 31, 2021, the Prichal and its Progress M-UM space tug were shipped to Baikonur by rail, after completion of joint tests with the simulators of the Nauka and the Zvezda modules, according to Roskosmos. The shipment to Baikonur also took place immediately after the docking of the Nauka module with the ISS.

Previous chapter: Progress M-UM space tug


Prichal Node Module, UM, and its Progress space tug are unloaded in Baikonur on August 11, 2021. Credit: RKK Energia

New launch date set for the Node Module

In the first half of 2020, the launch of the MLM Nauka module to the International Space Station, ISS, was shifted to the middle of the second quarter of 2021. In turn, the follow-on UM Prichal module was set to fly in the middle of the third quarter of the same year, or between three and four months after the Nauka.

In a provisional ISS flight manifest drafted by Roskosmos at the end of Summer 2020, the launch of Prichal was penciled for September 6, 2021, with the docking to Nauka's nadir port two days later.

At least three spacewalks aboard the Russian Segment of the ISS were expected to take place during a time period between the launches of Nauka and Prichal and one more sortie was planned soon after the arrival of the Prichal at the station. Russian cosmonauts would then make another trip to the exterior of the station in the early fourth quarter of 2021, followed by a series of six spacewalks at the end of 2021 and the beginning of 2022. This work should complete the integration of the two new spacecraft into the Russian Segment.

By the end of Fall 2020, the launch of Prichal slipped to November 24, 2021. By early November 2021, Prichal's instanteneous launch window was narrowed down to 16:06:32 Moscow Time. The launch vehicle was expected to insert the Progress M-UM/Prichal UM stack into a 193 by 240-kilometer orbit.

Prichal launch campaign begins

On August 9, 2021, Roskosmos confirmed that Prichal had arrived at Baikonur and on the morning of August 11, the joint Prichal/Progress M-UM stack was unloaded inside the spacecraft processing building at Site 254.

On the same day, specialists from RKK Energia installed the module and its space tug in their respective processing rigs at Hall 104 and began setting up the automated test network of the processing complex. As part of entry certification process, specialists conducted visual inspection of the Instrument Compartment, PAO, of the space tug and performed testing of the solar panel deployment mechanism on the Progress M-UM vehicle, RKK Energia said.

In the meantime, the Soyuz-2.1b launch vehicle for the mission arrived at Baikonur on August 18 and was unloaded inside processing facility at Site 112 on August 24, 2021. The components were then expected to be moved to the processing building at Site 31, where they would undergo assembly.


Prichal Node Module, UM, at the start of autonomous electric tests in Baikonur on August 24, 2021. Credit: RKK Energia

In the meantime, after the formal entry control procedure, the testing of Prichal officially started on August 28. Specialists from RKK Energia assembled ground testing equipment and cable network for autonomous electrical checks of the module, which was installed at the integrated test stand at Hall 104 of the processing building at Site 254.

In the following weeks, specialists conducted electric tests and functional tests of transit propellant lines (designed to deliver fuel and oxidizer from cargo ships to other modules of the Russian ISS Segment.)

On Sept. 20, 2021, Prichal was transferred into the 17T523MR vacuum chamber for a two-day air-leak testing of its pressurized hull. In parallel, electric tests started on the Progress M-UM space tug vehicle for the Prichal module at its work site. The trials included powering up equipment for flight control and navigation, telemetry and communications, attitude control and orbit tracking, thermal control and propulsion, Roskosmos said. The module was back at its work site by September 23.

Prichal meets its space tug


Prichal Node Module, UM, is being integrated with the Progress M-UM space tug on October 4, 2021.

By early October 2021, Prichal underwent tests of onboard automatic systems and the launch readiness simulation using ground diagnostics equipment. On October 4, the module was lifted from its work site and transferred to the processing rig of the Progress M-UM space tug, where it was connected to the adapter of the aggregate module, PAO, of the Progress with mechanical locks. Further integration activities included connections and tests of power, command and data interfaces between the module and the space tug.

On October 11, specialists began powering up the module's onboard systems and bringing them to launch readiness using ground testing equipment. The module and its space tug were then lowered in horizontal position and moved into the anechoic zone, where tests of the spacecraft's Kurs-NA radio system began on October 20. On October 28, Roskosmos announced that vacuum tests had been successfully completed.

On November 5, specialists conducted tests of solar panels aboard Progress space tug by exposing them to an array of electric lights. At the same time, the preparation of cargo items slated for delivery to the station aboard Prichal was in final stages, according to Roskosmos. These operations including loading of around 700 kilograms of cargo for the 66th long-duration expedition aboard the station, including food, personal protective equipment, water filters, repair hardware, hygiene and medical supplies.

On November 10, a meeting of technical management in Baikonur cleared the Progress M-UM space tug with the Prichal module for irreversible operations, including fueling and loading of pressurized gases.

On November 12, Roskosmos announced that a three-day process of pneumatic testing on all boosters comprising the Soyuz-2-1b rocket for the Prichal mission had been completed. By that time, specialists were setting up (another) round of tests, checking onboard system for monitoring propellant loading levels and conducting autonomous tests of the measurement system.

By November 13, fueling operations with Prichal were completed and it was returned to the spacecraft processing building at Site 254. The following day, the spacecraft was integrated with its launch vehicle adapter, which served as an interface for the payload fairing and provided connection of the command system aboard the Progress M-UM space tug and the Prichal module with the flight control system of the Soyuz 2-1b rocket. After the docking of the components, specialists conducted test activations of the onboard radio complex and other service systems, Roskosmos said. On the same day, the resulting stack was transferred to Hall 102 inside the spacecraft processing building at Site 254 for installation of the protective fairing, which was performed on November 16, completing the assembly of the payload section. On November 18, it was transported to the launch vehicle assembly building at Site 31 for integration with the Soyuz-2-1b rocket, which was completed by November 19. The rollout of the vehicle to the launch pad at Site 31 started at 5:30 a.m. local time on November 21.


Following the arrival at the pad, the vehicle was erected into vertical position and specialists began preparation for tests of the rocket and the spacecraft. Integrated tests of the launch vehicle were conducted in the second half of the day on November 22 and were successfully completed with the simulation of the flight from launch until the separation of the payload, Roskosmos said.

On November 23, considered a backup day in the on-pad processing, specialists conducted checks of propellant lines in preparation for fueling of the launch vehicle. The meeting of the State Commission, overseeing the preparations for launch, was scheduled at noon Moscow Time (10 a.m. local time) clearing the launch vehicle for fueling and launch.


Next chapter: Launching Prichal


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Article by Anatoly Zak; Last update: November 24, 2021

Page editor: Alain Chabot

All rights reserved


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Prichal undergoes testing at RKK Energia's checkout station, KIS, in Korolev on April 23, 2021. Click to enlarge. Credit: RKK Energia


Prichal is being prepared for departure to Baikonur circa July 2021. Click to enlarge. Credit: RKK Energia


The Progress M-UM space tug for the Prichal module is being installed in its processing rig at Site 254 in Baikonur around Aug. 11, 2021. Click to enlarge. Credit: RKK Energia


Prichal is being installed in its processing rig at Site 254 in Baikonur around Aug. 11, 2021. Click to enlarge. Credit: RKK Energia


Prichal module entered pre-launch processing on August 24, 2021. Its Progress-UM space tug was undergoing preparations for launch nearby. Click to enlarge. Credit: RKK Energia


Prichal is being transported into the vacuum chamber on Sept. 20, 2021. Click to enlarge. Credit: Roskosmos


Prichal's Progress space tug undergoes testing of solar panels on Nov. 5, 2021. Click to enlarge. Credit: Roskosmos


Prichal/Progress M-UM stack is integrated with the launch vehicle adapter on Nov. 14, 2021. Click to enlarge. Credit: Roskosmos


Prichal/Progress M-UM stack is installed in the processing rig at Hall 102 in Baikonur on Nov. 14, 2021, where it would be integrated with the payload fairing. Click to enlarge. Credit: Roskosmos