Integrating MLM with ISS




Russia considered scrapping troubled Nauka module in 2014

Faced with serious problems in preparing for launch their next big piece of the International Space Station, Russian engineers pondered leaving the ill-fated MLM/Nauka module behind and proceeding with the assembly of the Russian segment without this crucial element. The proposed architecture sans Nauka was found to be feasible but it would come at a high price.

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Here is how the completed Russian segment of the International Space Station, ISS, would look like, had Roskosmos canceled the launch of the ill-fated MLM Nauka module. Notable are the positions of the airlock on the UM Prichal module (center) and the European Robotic Arm, ERA, inherited from the grounded MLM and resettled on the NEM1 module (top).

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On Jan. 10, 2014, the head of RKK Energia Vitaly Lopota told the official ITAR-TASS news agency that the MLM module had been returned to GKNPTs Khrunichev on Dec. 31, 2013. Lopota promised that the repair schedule for the spacecraft would be issued by the end of the month. However only in April, Lopota was able to estimate that fixing all the damage to the crippled module would take no less than nine months, while its exact processing schedule would not be set until the end of the month. By that time, the launch of the MLM in 2015 was practically ruled out. To save at least some time, plans were made to ship the MLM from GKNPTs Khrunichev directly to the launch site, letting RKK Energia to conduct all final tests of the spacecraft in Baikonur, instead of its testing facility in Korolev, near Moscow.

On April 26, a poster on the web forum of the Novosti Kosmonavtiki magazine reported that the new development schedule had been approved, targeting February 2017 for the launch of the module. The tanks of the spacecraft were found to be unaffected by the contamination, however almost all propellant lines running on the exterior of the module would have to be replaced. Moreover, the module's engines had already exceeded their warranty and had to be replaced as well. The manufacturing of the new propulsion systems would take up to eight months, the poster said.

With its central position in the architecture of the Russian segment, the MLM's troubles also stall the launch of all subsequent Russian components of the station, including the Node Module, UM, (already under construction) and the NEM laboratory and power supply module, whose full-scale development started in 2012.

Given such a prolonged delay, combined with worsening political relations between Russia and its partners in the ISS project, the questions were raised whether the MLM module and the successive components of the Russian segment could be grounded until the assembly of the new all-Russian station in the post-ISS era. Under such a scenario, the troubled spacecraft could play a role of an early hub for the future orbital outpost. These speculations were reinforced by a statement of the Russian Vice-Prime Minister Dmitry Rogozin in 2014 that Russia would pull out from the ISS project in 2020.

Challenging architecture

After the discovery of a propellant system contamination in the MLM module in 2013, which would cost millions to fix and delay the assembly of the Russian ISS segment by years, leaders of the human space program in Russia naturally asked whether there were any alternatives.

During 2014, Russian engineers evaluated an option of giving up on the troubled MLM module and pressing ahead with the two follow-on components for the station: the Prichal Node Module, UM, and the Science and Power Module, NEM.

With two expansion docking ports on the already flying Zvezda Service Module, SM, of the Russian segment, the two follow-on components could be added one by one, either to the zenith (top) port to tower skywards, or to the nadir (bottom) port to extend downward from Zvezda relative to the Earth's surface. At the time, the nadir port on the Zvezda was occupied by the Pirs Docking Compartment, SO1, while the Poisk (a.k.a. MIM2) module was sitting on the zenith port. Although SO1 and MIM2 both featured SSVP docking ports on their outer ends, they were designed to receive seven-ton Soyuz and Progress cargo ships, and were considered unfit to hold much more massive modules like the 20-ton NEM lab. The same was true for the aft docking port on the Zvezda. That meant that either the SO1 module or the MIM2 module would have to be discarded before the docking of the new heavier modules.

At the same time, in order to berth the newly built Prichal module directly to the Zvezda Service Module, the former would need a special docking extension to provide enough clearance between the two components. Even with that extension, all but one of five extra docking ports available on the Prichal would be rendered useless, because of their close proximity to the Zvezda in the proposed arrangement.

Still, one available docking mechanism on the far side of the Prichal could be used for the attachment of the Science and Power Module, NEM.

The only option

After a careful analysis, Russian engineers have concluded that in the absence of Nauka, the most feasible option would be to dock the Node Module, UM, followed by the NEM lab to the zenith port on the Zvezda. Such an arrangement would closely resemble the original architecture of the Russian Segment formulated in mid-1990s. Thanks to that resemblance, Russian engineers hoped that the new design would be quickly vetted and approved by NASA and other ISS partners. Last but no least, in its new position, the NEM lab would end up with its solar panels facing upward, which would be ideal for catching solar energy.

In addition to the new extension on the main docking port of the Node Module, the Zvezda would also need minor modifications. Its Kurs-P (course) antennas, which respond to the incoming spacecraft during the rendezvous, would have to be repositioned and rewired for operation on the sky-facing expansion port.

Price to pay

Unfortunately, the essential loss of four docking ports on the Node Module during the lifetime of the ISS would not be the only payment for abandoning Nauka. First of all, the Russian Segment of the ISS would lose up to a half of its required volume for the installation of scientific equipment:

Required capacity
With Nauka module
Without Nauka module
Total power supply
19.8 kilowatts
19.9 kilowatts
18-30 kilowatts
Cargo storage capacity
25 cubic meters
25.2 cubic meters
25.2 cubic meters*
Volume for scientific payloads
24 cubic meters
24.2 cubic meters
12.9 cubic meters

*This figure includes around 5 cubic meters of free volume inside the Node Module, UM, and takes into account additional equipment needed for providing oxygen, as well as a toilet and sleeping quarters.


Theoretically, a considerable portion of the hardware from the canceled MLM module could be recycled for the benefit of the NEM module or other parts of the Russian Segment. The potentially compatible equipment included some structural components, onboard computers, avionics, communications, telemetry, rendezvous and docking mechanisms.

Some of the external equipment of the MLM module, which represented the highlight of its design, would require special accommodation measures. For example, a special airlock designed for exposing scientific experiments to the vacuum of space is already waiting for Nauka onboard the ISS, where it would be installed in its operational position with the help of the Canadian robotic arm.

In order to re-locate the airlock from the canceled Nauka to the yet-to-be-launched Node Module, the latter would have to be upgraded with a special docking mechanism, known as ASA-M.

Resettling the robotic arm

In the meantime, the European-built ERA robotic arm, which was also waiting for Nauka, could be permanently re-settled to NEM, with the help of two new external attachment points on the front section of the NEM module. Also, a remote-control console would have to be set up inside the NEM to operate the arm. During its launch, the NEM module could also carry the components of the robotic arm which are still on the ground. From its new location on the NEM module, the ERA arm could still easily reach to the science airlock and thus be used to extract cargo transferred from the pressurized volume of the station into the vacuum of space.

Still on the table

After being initially put forward in 2014, the idea of forfeiting the MLM/Nauka module has remained on the table until 2017. However Roskosmos never gave its authorization to implement the plan beyond a paper study, instead pressing ahead with repairs of the MLM spacecraft...


Next chapter: MLM module status in 2015


Written and illustrated by Anatoly Zak; Last update: July 14, 2021

Page Editor: Alain Chabot; Last edit: June 14, 2017

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As of 2014, plans were made to install an Earth-watching radar on the MLM module. Credit: RKK Energia


A depiction of the MLM module circa 2014 with its folded radiator. Credit: RKK Energia


The MLM/Nauka module, a.k.a. MLM, 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


In 2013, engineers found severe contamination inside the propulsion system of the MLM module, prompting them to consider grounding the spacecraft permanently.


Engineers are currently repairing MLM's tanks. Click to enlarge. Copyright © 2001 Anatoly Zak