Nauka (), also known as the Multipurpose Laboratory Module, Upgrade (MLM-U, ), is the primary laboratory of the Russian Orbital Segment of the International Space Station (ISS). Serving alongside the Rassvet and Poisk mini-research modules, Nauka conducts scientific experiments and stores research equipment.

Originally built as a backup for Zarya, the very first module of the ISS, Nauka's construction was halted in the late 1990s, when it was about 70% complete. After exploring various options, Roscosmos decided to convert the partially completed module into a laboratory. While the initial target launch date was set for 2007, and outfitting equipment for Nauka was delivered by Space Shuttle Atlantis in 2010 attached to the Rassvet module, numerous delays and technical issues delayed the launch by 14 years.

Nauka finally launched on 21 July 2021 at 14:58:25UTC from the Baikonur Cosmodrome atop a Proton-M rocket. Like most of the Russian modules, Nauka operated autonomously and after a flight lasting about eight days, Nauka docked to the nadir (Earth facing) port of the Zvezda module on 29 July 2021 at 13:29:01UTC. However, after docking, a software glitch led the module's thrusters to keep firing, causing the entire space station to flip over one and a half times, before the module ran out of fuel. The crew was able to null the rotation, and return the station to its normal orientation. While the situation was tense and NASA declared a "spacecraft emergency", they later said that the situation did not endanger the lives of the ISS crew.

The addition of Nauka is the first major expansion of the Russian Orbital Segment in over 20 years. Cosmonauts would conduct twelve spacewalks over two years outfitting the module with equipment, much of it brought aboard the Rassvet module in 2010 and Prichal, a multi-port docking module was added to Nauka in November 2021.

Description Nauka is the primary laboratory of the Russian Orbital Segment, operating in conjunction with the Mini-Research Modules Rassvet and Poisk. It is used to conduct experiments and store scientific instruments, and can also serve as a backup service module for the ISS. Nauka is based on the Functional Cargo Block (FGB) design. It is long and wide, and is made of stainless steel, aluminium alloy, kevlar, and ceramic-wool insulation, totalling a mass of .

Nauka has two SSVP-M docking ports; the passive nadir port is used to attach Prichal to the station, while the active zenith port is used to attach Nauka itself to the station via Zvezdas nadir port. SSVP-M is a hybrid variant of the SSVP docking system that combines its traditional probe‑and‑drogue soft-capture mechanism with the APAS-95 hard-docking collar. While this is incompatible with Soyuz and Progress' standard SSVP-G ports, a temporary docking adapter SSVPA-GM that converts Naukas nadir port from SSVP-M to SSVP-G was installed to allow them to dock. This adapter was removed upon the arrival of Prichal because, although it is the second module after Rassvet to use a port initially used by Soyuz or Progress spacecraft, it is not able to dock to SSVP-G ports like the Rassvet module. As a result, the Prichal module with its active hybrid docking port was only able to dock to the reconfigured port. With its docking, the number of docking ports on the ISS Russian Orbital Segment increased to eight. Another one was an Active AS-G forward port to allow the Airlock ShK module to berth with Nauka.

Full guidance and navigation control, enabled by an attitude control system using MDDK thrusters, provide roll control to the station using its advantageous position far from the station's fore-aft axis, which provides the greatest mechanical advantage for roll corrections of all the station's thruster-equipped modules. Nauka is also able to collect and store propellant delivered by Progress spacecraft and transfer it to Zvezda.

The European Space Agency's (ESA) European Robotic Arm located on Naukas exterior enables the installation, removal or replacement of external experiment payloads; the transfer of payloads through the science airlock; and visual inspections of the station. It can support spacewalks by providing foot restraints, tether points, and control panels both on the inside and outside of the station. Nauka contains life support equipment including an oxygen production system capable of supporting six crew, a galley, a toilet with a urine recycling system, and one of the three sleep stations aboard the Russian Orbital Segment. There is a large observation window similar to Destiny's nadir window for the crew on the aft side of the docking sphere, towards the nadir port, while one 9-inch-wide window hatch is on the forward port for the airlock module, similar to the two windows on the Kibo Pressurized Module. Science (or Experiment) Airlock ShK

The airlock, Shk, is designed for a payload with dimensions up to , has a volume of , weight of 1050 kg and consumes 1.5 kW of power at the peak. Prior to berthing the MLM to the ISS, the airlock was stowed as part of MRM1. On 4 May 2023, 01:00 UTC, the chamber was moved by the ERA manipulator and berthed to the forward active docking port of the pressurized docking hub of the Nauka module. It is intended to be used: for extracting payloads from the MLM docking adapter and placing them on the outer surface of the station; enable science investigations to be removed, exposed to the external space environment, then returned inside while being maneuvered with the European robotic arm. for receiving payloads from the ERA manipulator and moving them into the internal volume of the airlock and further into the MLM pressurized adapter; for conducting scientific experiments in the internal volume of the airlock; for conducting scientific experiments outside the lock chamber on an extended table and in a special organized place. for launching cubesats into space, with the aid of ERAvery similar to the Japanese airlock and Nanoracks Bishop Airlock on the U.S. segment of the station.

Development

In the 1990s, Roscosmos' original plan for the Russian Orbital Segment included two Russian Research Modules and a Universal Docking Module based on the FGB design to be located at Zvezdas nadir port. A backup flight article for FGB-based Zarya, known in production as FGB-2, was originally planned to serve as the Universal Docking Module, though its construction had been halted at 70% completion in the late 1990s. By August 2004, Roscosmos decided to scrap the two research modules in favour of flying FGB-2 as a single research module known as Nauka. A joint Astrotech-Energia concept for a Commercial Enterprise Module-based Nauka, proposed to Roscosmos around this time, was rejected. In 2005, Roscosmos brokered a deal with the ESA to launch their European Robotic Arm with Nauka, with its spare elbow joint to launch with Rassvet.

While Roscosmos had originally hoped Nauka would be ready for launch by 2007, multiple delays pushed the prospective launch date back progressively to 2014. Acceptance tests of Nauka in late 2013 found leaks in the propulsion system's fueling valve and contamination, so Energia returned the module to Khrunichev for twelve to eighteen months of repairs. Naukas prospective 2015 launch was delayed again after more fuel valve leaks damaged the module's exterior plumbing, necessitating its replacement. Metallic dust contamination in the module's fuel tanks in 2017 caused three more years of delays, as initial repairs were unsuccessful, and the installation of a new single-use fuel system based on the Fregat upper stage was considered as a solution. However, in late 2019, the original tanks were successfully repaired, rendering the planned Fregat-based tanks redundant and paving the way for a 2019 or 2020 launch.

Targeting an early-to-mid-2020 launch, Nauka's Proton-M launch vehicle was assembled and shipped to the Baikonur Cosmodrome in February. However, Nauka needed another fuel tank valve replacement, along with further tests necessitated by an expiring warranty following years of delays. The testing – which could only take place at Energia in Russia instead of Kazakhstan, where Baikonur is located – was completed in May 2020, around the same time the new fuel tank valves were shipped to Baikonur. Efforts to launch Nauka were affected by the outbreak of COVID-19 in Europe in early 2020, which led to suspension of all work in March, April, and July, and a sizeable reduction in workforce throughout the year, as part of measures to prevent the potential spread of the disease. Nauka finally arrived in Baikonur in August 2020, along with its solar panels and the European Robotic Arm shortly afterwards. The loading of cargo and supplies onto Nauka began on 11 September 2020, while its MMOD armor and batteries were installed. Throughout October and November 2020, Expedition 65 cosmonauts Pyotr Dubrov and Oleg Novitsky, who were to be responsible for Naukas installation to the station in orbit via numerous extravehicular activities, conducted two Crew Equipment Interface Tests during which the module was powered on for the first time with various components deployed, and the cosmonauts inspected and toured the vehicle's exterior.

By November 2020, Nauka had been put through 306 of the 754 tests needed before it could be processed for launch, and by January 2021 80% of the tests were complete. Throughout January and February, Naukas tanks, thrusters, and automated docking system underwent final testing, along with the European Robotic Arm. In March, two more Crew Equipment Interface Tests with Dubrov and Novitsky took place, and Naukas launch was delayed one final time from May to July 2021, following further COVID-19-related restrictions and complications with traffic on the International Space Station. In May, Nauka passed Roscosmos' flight readiness review, underwent a final round of pressurization and leak tests, and the SSVP docking adapter, the solar panels, and the European Robotic Arm were attached to the module's exterior. One final Crew Equipment Interface Test was conducted with cosmonaut Aleksandr Skvortsov and his backup Sergey Prokopyev before Nauka's encapsulation in the Proton-M's payload fairing in June. On 28 June, Nauka was successfully mated with its Proton-M launch vehicle and rolled out to Site 200 on 17 July.

Launch

On 2 May 2021, the launch schedule was posted online; it involved the launch of Progress MS-17 on 30 June to deliver outfitting hardware to the station and plugs to fix the leak in the Zvezda service module. Before it docked, Novitsky and Dubrov performed a spacewalk to remove equipment and cables from Pirs in preparation for undocking. Site 200, from which Nauka and its Proton-M were to launch, were modified to supply chilled air and fuel the vehicle as it sat on the pad; the same modifications were made to Site 81 when Mir, Zarya, and Zvezda were launched from it. On 7 June, work at Site 200 was completed in preparation for the assembly of the launch vehicle and the rollout of Nauka to Pad 39 at the facility.

On 30 June 2021, fueling began, but a problem with the spacecraft's guidance sensors was detected and Nauka was rolled back to the instrumentation and test facility at Site 254. The upper fairing was removed and rolled away while workers using safety harnesses changed and replaced the sensors and reinstalled the MLI. On 1 July, more imperfections were found requiring a full scrub down and systems had to be removed and replaced. On 3 July, the fairing was reattached and Nauka was powered on to test the sensors before it was reloaded onto the transfer car and redelivered to the airlock where it was placed on a flatcar for delivery to Site 31 for fueling.