Russia considered scrapping troubled Nauka module
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.
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).
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 manned 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:
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...
Read (and see) much more about this and many other space developments in Russia
Written and illustrated by Anatoly Zak; Last update: March 29, 2020
Page Editor: Alain Chabot; Last edit: June 14, 2017
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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