Prichal Node Module, UM

The Prichal Node Module, UM, was designed for the Russian Segment of the International Space Station, but potentially, it could also serve as a hub of the future new station. The Prichal was designed to be attached to the MLM Nauka module, providing five extra docking ports to the Russian Segment and giving a potentially unlimited life span to the future outpost.

Previous chapter: The MLM Nauka module for the Russian segment of ISS

The Prichal Node Module. Credit: RKK Energia

Node Module at a glance (328):

Liftoff mass (with Progress-MS space tug)
7,290 kilograms
In-orbit mass
4,000 kilograms
Pressurized volume
14 cubic meters
Cargo to be delivered with the module
1,000 kilograms
Number of docking ports
Launch vehicle
Soyuz-2-1b (14S54) No. S15000-049
Launch date
2021 November (planned)
Launch site
ISS, Russian Segment, MLM's nadir port

The Node Module concept

In the mid-2000s, financial problems forced the Russian space agency to redesign its segment of the International Space Station, ISS. After considering various options, engineers at RKK Energia, the nation's prime contractor in the ISS project, proposed to add a new element called "Uzlovoi Modul," UM for short, or Node Module in English. The spacecraft was later dubbed Prichal - a Russian for "pier."

Despite its small size, this four-ton, ball-shaped structure got to play an important role in the Russian space program. The primary task of the Node Module was to accommodate a pair of Science and Power Modules, NEMs, which were intended to replace the canceled Science and Power Platform, NEP. However, the Node was also conceived to serve as the only permanent element of the future Russian successor to the ISS, if required.

Equipped with six docking ports, the Node Module could potentially work as the single permanent core of the future station with all other modules coming and going as their life span and mission determines. Thus, an orbital base with the Node Module at its center could be maintained in space practically indefinitely. This would be a key feature of the new outpost, making it drastically different from previous multi-modular space stations such as the Russian Mir, Mir-2 and the ISS, whose "in-line" architecture makes it virtually impossible to replace their original modules.

Mission Profile

For its ride to the station, the Prichal Node Module will be integrated with a custom version of the Progress cargo ship and both will be launched on a standard Soyuz-2 rocket from Baikonur. The Progress will use its own propulsion and flight control system to deliver and then permanently attach the Node Module to the nadir (Earth-facing) docking port of the MLM module on the Russian Segment of the ISS. During its trip to the station, the Node will also make a one-time delivery of 1,000 kilograms of cargo.

Besides its five free docking ports, the Node Module will add 14 cubic meters of pressurized volume to the station.

The zenith (upward facing) docking port of the Node Module is equipped with a so-called active hybrid docking port, which enables its docking with the MLM module and makes it capable of safely withstanding the high dynamic loads from future add-on spacecraft. The remaining five ports are so-called passive hybrids, enabling the docking of Soyuz and Progress vehicles as well as heavier modules and future spacecraft with modified docking systems.

Stuck on the ground

As of 2008, the Node Module was expected to fly as early as 2012. However during 2009 and 2010, its launch date began drifting in a domino effect of complications with the development of the MLM module.

On Jan. 15, 2011, RKK Energia announced that its Scientific and Technical Council, NTS, had reviewed and approved the preliminary design of the Node Module and associated hardware, including:

  • A special version of the Progress cargo ship designated the Progress M-UM spacecraft-module, intended for the delivery of the Node Module to the station;
  • The space payload section, KGCh, for the Progress M-UM;
  • The adaptation of the Soyuz rocket for the launch of the Progress M-UM spacecraft-module.

The NTS meeting chaired by Deputy Designer General V. P. Legostaev was also attended by RKK Energia's President Vitaly Lopota and Deputy Designer General Nikolai Zelenshikov, the company said. According to the press-release, the launches of both the Node Module and of the preceding MLM multi-purpose module were scheduled for 2012.

In May 2012, Roskosmos ordered the production of a Soyuz-2-1b rocket to carry the Node Module into orbit. By August of that year, a NASA schedule of ISS missions showed the launch of the Progress M-UM (No. 303) vehicle with the Node Module on Nov. 15, 2014. However, in 2013, newly discovered contamination inside the MLM module left in limbo all further assembly of the Russian Segment.

According to NASA, by the end of 2013, the launch of the UM module was expected no earlier than May 2016. During 2014, the launch shifted to 2017 and by 2015, the launch slipped to 2018. The station's flight manifest surfaced in April 2015 indicated the launch of the Node Module in the third quarter of 2018.

According to the October 2017 schedule, the Node Module was to fly 7.5 months after the launch of the MLM Nauka multi-purpose laboratory in March 2019.

According to the flight manifest drafted by Russian officials at the time, the launch of the Prichal Node Module along with the Progress-MS-UM spacecraft was set for Nov. 14, 2019. Two days later, the Progress/Node stack was to dock to the MLM Nauka module. Around a month later, the propulsion section of the Progress-MS-UM spacecraft was to separate from the Node, revealing its nadir-facing docking port and making it available for other ships visiting the ISS.

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.

Prichal launch campaign begins


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

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. 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

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.


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

On October 11, 2021, specialists of the the Yuzhny branch of the TsENKI infrastructure center and RKTs Progress completed the integration of the four first-stage boosters with the second (core) stage of the Soyuz-2-1b rocket for the Prichal mission inside the vehicle assembly building of Site 31. The assembled stack was then placed on a storage site. The rocket's boosters carried insignia dedicated to the 800th anniversary of the Russian city of Nizhny Novgorod.


Next chapter: Integrating Prichal Node Module with ISS (INSIDER CONTENT)

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Writing, photography and illustrations by Anatoly Zak, unless credited otherwise; Last update: October 12, 2021

Page editor: Alain Chabot; Edits: October 25, 2017, August 11, 2021

All rights reserved


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An early concept of the Node Module. Credit: RKK Energia

Russian segment

A 2009 scale model depicting future configuration of the International Space Station, included a node module at the heart of the Russian segment. Click to enlarge. Copyright © 2009 Anatoly Zak


The node module could also serve as a core of the future Russian space station. Copyright © 2009 Anatoly Zak


In a proposal for the High-latitude Space Station, VShOS, a specialized Node Module, UM, with six docking ports (right), links up with the MLM module, after its departure from the Russian segment of the International Space Station. During its stay at the ISS, the MLM would be outfitted with a radiator and a small airlock, which were originally launched into orbit with the MIM1 module. Click to enlarge. Copyright © 2015 Anatoly Zak


The Node Module during its assembly at RKK Energia in early 2010s. Click to enlarge. Credit: RKK Energia


The Node Module was to be equipped with four passive hybrid docking ports. Click to enlarge. Credit: Roskosmos


A custom-built space tug based on the Progress-MS cargo ship will be used to boost the Prichal Node Module from its initial orbit to the ISS. Click to enlarge. Credit: RKK Energia


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


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


The assembly of the boosters stages of the Soyuz-2-1b rocket for the Prichal mission was completed on Oct. 12, 2021. Click to enlarge. Credit: Roskosmos