21.08.2020

The newest habitable module for the International Space Station (ISS), Nauka, has arrived at the Baikonur Cosmodrome in Kazakhstan for final preparations before launch. The module’s launch – which has been delayed for more than 13 years – will mark the resumption of Station expansion.

Nauka is currently scheduled to launch on a Proton-M rocket in April 2021 and will be attached to the ISS at the location where the Pirs Docking Compartment is currently located.
Nauka’s history

The module that would become Nauka – Russian for “Science” – was first constructed as the backup to the currently-on-orbit Zarya module. As such, both are of a similar design called the “Functional Cargo Block” (FGB).

The FGB design traces its roots to the Soviet TKS spacecraft that was designed in the 1960s to serve as a crew and cargo resupply vehicle for the Soviet Union’s Salyut space stations. It was comprised of two parts – the VA spacecraft and Functional Cargo Block – both of which could also operate independently.

Cutaway diagram of the TKS spacecraft. The pressurized volume is outlined in bold. The cylindrical FGB is visible on the left and center, while the conical VA and maneuvering system is visible on the right. Credit: NASA

The VA spacecraft itself was initially designed as a lunar crew vehicle – similar to the Apollo Command Module. It would have carried up three crew members during launch and landing and was notable in that it was intended to be reused -although this was only demonstrated once.

For lunar missions, the VA would have launched on a Proton rocket with a service module attached to allow for a longer mission. However, this configuration was shelved in favor of the Soyuz 7K-L1 design (also known as “Zond”), which went on to fly 12 times. After it was rejected for the Soviet lunar program, the VA was repurposed to become part of the TKS spacecraft.

The Functional Cargo Block under this design served as a service and storage module. It featured a spacious pressurized volume in its center, meant for cargo storage and docking equipment. On the outside of the FGB were fuel tanks, maneuvering engines, solar arrays, and docking port.

The TKS flew four times and docked to Salyut stations three times. None of those missions were crewed.

Following the cancellation of the TKS, the Soviet space program soon realized the other possibilities the FGB design could offer.

In 1987, the Kvant-1 module was launched to the Mir space station. Rather than having its own control system, it was delivered to the station by a Functional Service Module – derived from the FGB.

Several other Mir modules were themselves derived from the FGB, including Kvant-2, Kristall, Spektr, and Priroda. Repurposing the FGB design for several of Mir’s modules saved both time and money.

Later in 1987, the Polyus spacecraft was launched on the maiden flight of the Energia rocket. Polyus was an orbital laser weapon capable of destroying satellites. It was maneuvered and powered by a modified FGB, a surplus from the TKS program. Due to a faulty guidance system, the FGB rotated Polyus incorrectly and fired the engines while facing backward. Polyus did not achieve orbit, and burned up over the Pacific Ocean.

In 1998, the next FGB-derived module – Zarya – launched on a Proton rocket. Zarya was the first module of the International Space Station, and provided power, control, and propulsion for the early Station. It was built by Russia under a contract from NASA.

In case of a launch failure, a backup to Zarya was built from spare components. Named FGB-2, its construction was halted at around 70% completion.

After the successful launch of Zarya, FGB-2 was placed in storage with no certain future. Several plans were proposed for incorporating the module into the ISS. These included it becoming a docking hub, laboratory, or even a single-use resupply vehicle.

Eventually, Roscosmos – the Russian space agency – accepted a proposal to convert FGB-2 into the “Multipurpose Laboratory Module”, or MLM. At this point, the module was expected to launch in 2007.

As its name suggests, the MLM would be a multipurpose – although mainly scientific – module. It would feature crew quarters, research stations, propulsion, solar arrays, a robotic arm – named the European Robotic Arm – and an experiment airlock, among others.

However, not all of those would be brought to orbit with the MLM.

The Rassvet Mini Research Module was launched to the ISS in 2010 onboard the Space Shuttle Atlantis. The module was intended to be a small docking and laboratory module. In addition, Rassvet was tasked with bringing several of the MLM’s components to the Station.

Rassvet launched on Atlantis with the MLM’s radiator, experiment airlock, and a spare joint for the European Robotic Arm – all of which will be installed onto the MLM after it arrives at the Station.

The MLM will also feature propulsion systems sufficient to rendezvous and dock autonomously with the ISS after launch. The onboard fuel tanks can be reused for propellant storage once attached to the Station. The MLM’s solar arrays will also help lower the Russian segment’s reliance on the Station’s main set of solar arrays that are technically part of the U.S.’s segment.

The new module will contain water and air purification systems, a new galley, and toilet. Its thrusters can also be used as a backup to control the Station, should those on Zvezda fail.

The MLM was later formally named “Nauka”, a Russian word for “science”.

After its arrival and fitting-out, Nauka will become the primary laboratory module on the Russian segment. Currently, Russia has two small laboratory modules – Rassvet and Poisk – both of which will be dwarfed by Nauka.

Additionally, Nauka will take the title of the heaviest Russian module on the Station, at 24.2 tons. Zvezda currently holds this honor, at 20.3 tons.

Nauka’s future docking port at the ISS – Zvezda nadir, or Earth-facing, docking port – is currently occupied up by the Pirs Docking Compartment.

Pirs was launched in 2001 and serves as a docking port for Soyuz and Progress spacecraft. In addition, it features storage space and two hatches for spacewalks.

To clear the docking port for Nauka, a Progress cargo resupply spacecraft will be used to remove Pirs from the Station. This is scheduled to be performed by Progress MS-15, which launched in July 2020 and docked to Pirs three hours later.

The Russian crew on the Station will perform spacewalks to prepare Pirs for removal.  At the end of Progress MS-15’s mission – assuming Nauka remains on track for launch in April 2021- instead undocking Progress from Pirs, the hooks and latches connecting Pirs to Zvezda will be retracted and Progress will ease the docking compartment away from the Station.

A few days later, Progress deorbit with Pirs for a destructive reentry into Earth’s atmosphere.

Pirs will become the first module of the Station to be permanently removed and destructively disposed of. At present, no plans exist to remove any of the other original modules from the Station on either the Russian or U.S. (which includes Canada, Japan, and ESA) side of the outpost.

But Nauka will not be a one-off addition, but instead will mark the resumption of major station expansion.

In the third or fourth quarter of 2021, the Prichal – Russian for “pier” or “dock” – node module will be launched to the Station. It will be carried by a modified Progress spacecraft, and docked to the Earth-facing port of Nauka.

Renderings of the Prichal node module. The top port on the right view will attach to the Earth-facing port of Nauka. Credit: RSC Energia

Prichal features six docking ports – one of which will be used to connect it to Nauka. The other five will be available for use by visiting Soyuz or Progress vehicles, and later for additional new modules. The port directly opposite of Nauka is equipped to transfer fuel to the Station from Progress spacecraft.

When Prichal launches to the ISS, it will bring along one ton of cargo.

The first permanent module to make use of one of Prichal’s ports will be the Science-Power Module 1, or NEM-1.

NEM-1 is a clean-sheet design,, comprised of two segments – one pressurized and one unpressurized.

The cylindrical pressurized segment will have an internal volume dwarfing that of Nauka. It will contain a modular rack system for research, crew quarters, and storage – similar to that in the modules of the United States Orbital Section. The modular system enables easier reconfiguration of internal elements.

Rendering of NEM-1. The wide pressurized section is seen on the bottom left, and the smaller unpressurized section (featuring two large solar arrays) is seen in the center. Credit: RSC Energia

NEM-1’s pressurized segment will also be home to a new life support system, along with additional crew quarters.

The unpressurized segment would feature communications equipment, radiators, and two large solar arrays. The arrays would generate 18 kilowatts of power, 12 of which could be sent to other modules in the Russian segment. The new antennas on NEM-1 will enable continuous communication through Russian relay satellites.

NEM-1 has faced limited funding since 2016. However, Russian officials still plan for a launch in 2021 or 2022.

Structural testing on a ground test article of the module was completed in 2019.

NEM-1 will be launched on a Proton rocket with a custom fairing. The walls of the pressurized segment will be left exposed, and a conical fairing will cover the docking port. A separate cylindrical shroud will cover the unpressurized segment.

Additional Russian modules have been proposed – such as an airlock and an autonomous, free-flying laboratory module. These plans are still in early development.

On the U.S. side of the complex, Axiom plans to add a module complex to support commercial and industry use of the Station.

Quelle: NS