MLM tanks



Integrating MLM with ISS





From FGB-2 to MLM:
Origin of the Nauka module

The MLM multi-purpose module (a.k.a. FGB-2 or 77KML No. 17901) originated as a backup copy to the first element of the International Space Station -- the Zarya control module, which was launched in November 1998.

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An isolated view of the MLM module in deployed position. Copyright © 2012 Anatoly Zak

The evolution of the MLM's specifications:

Liftoff mass
21.2* - 20.3** tons
20.257 tons
Mass in orbit (with add-on radiator, airlock and other hardware)
24.0 tons
24.2 tons
Pressurized volume
70 cubic meters
70 cubic meters
Available volume for cargo storage
8 cubic meters***
Available volume for scientific payloads
8 cubic meters
6 cubic meters
Available power supply for scientific payloads
up to 2.5 kilowatts
up to 2.5 kilowatts
Launch vehicle
Planned launch date
2013 Dec. 11*
2017 Dec. 6
Planned docking date to the Russian segment of ISS
2013 Dec. 20*
2017 Dec. 15
Docking location
13.1 meters
Solar panels span
23.9 meters

*RKK Energia as of December 2012 (20.7 tons according to other sources)

**GKNPTs Khrunichev as of December 2012

*** 4.9 cubic meters, according to 903

A sibling of the first station piece

The first of two sibling spacecraft -- the Zarya FGB control module -- was built during the 1990s by Moscow-based GKNPTs Khrunichev under a contract with the Boeing company. Although the agreement funded only a single vehicle, Khrunichev used available spare parts and its own funds to build a backup module, in case the original spacecraft was destroyed or rendered unusable in a launch accident. With the successful launch of Zarya in November 1998, its partially completed sibling was mothballed.

By the time the original Zarya had docked successfully to the Zvezda service module in July 2000, FGB-2 was about 65 percent ready, according to GKNPTs Khrunichev.

At that point, Russian space officials considered several potential new roles for the remaining spacecraft in the ISS program, including its use as a heavy supply ship for the Russian segment of the station.

In the middle of 2000, Boeing announced that it had partnered with Khrunichev to "commercialize" the FGB-2. The move put Khrunichev/Boeing team on a collision course with RKK Energia and Spacehab, who at the end of 1999 claimed the same docking port on the ISS (nadir or Earth-facing docking port on the Zarya module) for their commercial Enterprise module. In the end, neither of the two projects had materialized.

A new role for FGB-2

Published: 2001 August 10

During 2001, in an effort to save money on the virtually stalled development of the Russian segment of the International Space Station, GKNPTs Khrunichev proposed to use the FGB-2 spacecraft as a base for the Universal Docking Module, USM, (Insider Content). The USM would serve as a hub for up to three Russian research modules, however, work on it all but stopped due to lack of funds.

The concept of using the FGB-2 as a Universal Docking Module had been considered in previous years, however the amount of work required for modifying the module for the task would have not justify the effort. For example, the transfer compartment, GA, on FGB-2 had to be repositioned and equipped with three additional docking ports to receive future science modules. However by 2001, Khrunichev officials argued that in light of the financial situation at the time, Russia had no chance of building any of its science modules during the ISS lifetime.

According to Khrunichev, it would be enough to add a single docking port to the FGB-2 in order for it to serve as the Universal Docking Module. In August 2001, Khrunichev and RKK Energia -- the main Russian contractor on the ISS -- reportedly agreed on the use of the FGB-2 as the Universal Docking Module, USM.

According to that plan, the FGB-2 module would dock to the Earth-facing (nadir) port on the Zvezda service module, i.e. the same port where the USM module was expected to reside. Such a configuration would leave the "nadir" port on the Zarya module for the RKK Energia's proposed Enterprise module.

In addition to the new docking port, the FGB-2's solar panels and a number of other systems would have to be modified, in order for the spacecraft to serve as a replacement for the USM.

Khrunichev representatives said that the FGB-2 could be prepared for launch within two years after a decision on its mission had been made. From around 2001 and until 2004, the launch of the FGB-2 module to the ISS was scheduled for 2007.

Multipurpose Laboratory Module, MLM

Around 2004, it was proposed to convert the FGB-2 module into the Multi-Purpose Laboratory Module, MLM, or 77KML, according to its industrial designation. At the time, it was expected to dock the spacecraft to the nadir port of the Zarya FGB module. This configuration was approved by the decision of Rosaivakosmos on February 16, 2004, under leadership of Yuri Koptev and reconfirmed by a newly appointed head of Federal Space Agency Anatoly Perminov on July 20, 2004.

In order to have enough clearance during berthing with the Zarya, the front active docking port of the MLM was to be installed on a special extension adapter. According to the same plan, the MLM module would be followed to the ISS by a research module, which would be docked at the nadir port of the Zvezda Service Module. However this plan was eventually re-worked, in the course of development of the experimental project for the MLM module, which was taking place around 2005.

On July 31, 2006, the Federal space agency, Roskosmos issued a Decision No. AP-99 "On the clarification of the technical design and the work order of the multi-purpose module (MLM)."

On November 3, 2006, RKK Energia and the Russian space agency, Roskosmos, signed a contract calling for the development of the Multipurpose Laboratory Module, MLM. At the time, the full-scale development of the module was expected to start in 2007, and its launch was targeted for 2009.

In the new configuration, the MLM module would accommodate service systems for the Russian Segment of the ISS and scientific payloads. The European-built ERA manipulator and the DMS-R multi-function computer would also be installed onboard. A special automated airlock for moving payloads from the interior of the station to the vacuum of space would be installed on the lower section of MLM.

To be delivered into space by the Proton rocket, the module would have an initial mass of 20,700 kilograms and provide 70 cubic meters of pressurized volume. Around eight cubic meters would be available for cargo storage and the same volume would be left for the installation of the scientific payloads. The module would sport a total of 12 workstations for various instruments and experiments. Special incubators and vibration-protected platforms for sensitive material-science research would be available.

Prior to the MLM launch, the Pirs Docking Compartment, SO1, which had occupied the nadir (Earth-facing) docking port of the Zvezda service module, was to be discarded along with a departing Progress cargo ship. It would then be directed to the Earth atmosphere to burn up. The MLM would then use its own engines to rendezvous with the station and dock to the freed nadir port on Zvezda.

Around a year or two after the MLM arrival at the station, a 4,000-kilogram ball-shaped Node Module would be docked to the outer end of the MLM, enabling the addition of as many as five spacecraft to the Russian segment of the ISS.

On November 9, 2007, the Collegium of the Federal space agency issued an order No. 22p "On the implementation of the Russian Segment program for the International space station in 2008-2015." The document called for a two-phase construction of the Russian Segment, where the first phase would be concluded with the addition and outfitting of the MLM module. The second phase would include the addition of the Node Module and the Science and Power Module, NEM.

On December 26, 2008, Designer General of RKK Energia Vitaly Lopota signed the 33-page technical assignment TZ.0011.009-516GK for the development of the rocket and space complex designated 516GK Proton-MLM which was to integrate the Proton vehicle with the MLM module. The document was cleared by the military acceptance service 1382 of the Russian Ministry of Defense on Jan. 29, 2009.

MLM development starts

By the beginning of 2008, the launch date of the MLM slipped from 2009 to 2011. Until May 2009, the MLM was promised to take off in December 2011. During the May 29 press-conference at the mission control in Korolev, Aleksei Krasnov, the head of manned space flight at Roskosmos, said that launch was expected in the first quarter of 2012. However in the October 2009 NASA schedule, the mission was still marked for launch in December 2011.

In August 2011, the Director General of GKNPTs Khrunichev, Vladimir Nesterov, said that a prototype of the MLM module designed for electrical tests would be delivered to RKK Energia before the end of the month, despite technical issues associated with changes in the module's design documentation. (503) In reality, the electrical prototype was delivered from the production plant at GKNPTs Khrunichev to RKK Energia on December 8, 2011.

By the Fall of 2011, the launch of the module was postponed from December 2012 to June 2013, at the earliest. According to unofficial reports, in 2012, the launch slipped further to 2014.


Next chapter: MLM development in 2012

Article, photography and illustrations by Anatoly Zak; Last update: August 24, 2021

Page Editor: Alain Chabot; Edits: October 21, 2008; September 30, 2016

All rights reserved


insider content



An early NASA rendering showing the MLM module docked to the nadir port of the FGB Zarya control module rather than the Zvezda Service Module. Credit: Roskosmos


Eventually, planners decided to dock the MLM to the nadir port of the Zvezda Service Module.

The FGB-2 module, minus its solar panels, sits in the assembly shop at Khrunichev enterprise in Moscow in August 2001. Protective red boxes cover attitude control engines. Copyright © 2001 Anatoly Zak

The FGB-2's docking adapter in its original configuration. Additional docking ports would have to be installed on the section to adapt the module for the new role of the Universal Docking Module, UDM. By 2008, developers decided to add a special Node module to that section to enable further expansion of the Russian segment. Copyright © 2001 Anatoly Zak

The interior of the FGB-2 module viewed from the docking adapter section toward the front docking port. Copyright © 2001 Anatoly Zak


Electric prototype of the MLM module arrived at RKK Energia on December 8, 2011. Click to enlarge. Credit: GKNPTs Khrunichev


The training mockup of the MLM module in Star City circa 2012. Click to enlarge. Credit: NASA