Soyuz MS

The Soyuz MS (; GRAU: 11F732A48) is the latest version of the Russian Soyuz spacecraft series, first launched in 2016. The "MS" stands for "modernized systems," reflecting upgrades primarily focused on the communications and navigation subsystems. An evolution of the Soyuz TMA-M spacecraft, the Soyuz MS features minimal external changes, mainly in the placement of antennas, sensors, and thrusters. It is used by Roscosmos for human spaceflight missions.

Soyuz MS-01 conducted its maiden flight on 7 July 2016, heading to the International Space Station (ISS). The mission included a two-day checkout phase to validate the spacecraft’s new design before docking with the ISS on 9 July 2016. After remaining docked to the ISS for 113 days, the crew of MS-01 returned to Earth on 30 October 2016, safely landing on the Kazakh Steppe.

The spacecraft has experienced one in-flight abort during the Soyuz MS-10 mission. Shortly after the four boosters of its Soyuz FG carrier rocket separated, one collided with its core stage. The spacecraft’s onboard computer activated the launch escape system, which performed flawlessly, quickly pulling the reentry and orbital modules away from the failing rocket. Once at a safe distance, the system jettisoned the reentry module, allowing it to descend to the ground under parachutes. The crew landed unharmed.

Design

Like all previous variants, the Soyuz MS spacecraft consists of three parts (from forward to aft in space and top to bottom when mounted on a rocket):
* A spheroid orbital module,
* A small aerodynamic descent module,
* A cylindrical instrumentation/propulsion module

The orbital and descent modules contain the pressurized habitable living space. By moving as much equipment and space as possible into the orbital module, which does not have to be shielded or decelerated during re-entry, the Soyuz three-part craft is larger and lighter than two-part designs. By comparison, the Apollo spacecraft's pressurized command module provided a crew of three of living space and had a reentry mass of ; while the Soyuz MS provides the same crew with of living space while the reentry module weighs .

Soyuz can carry up to three cosmonauts and provide life support for them for about 30 person-days. The life support system provides a nitrogen/oxygen atmosphere at sea level partial pressures. The atmosphere is regenerated through KO₂ cylinders, which absorb most of the CO₂ and water produced by the crew and regenerates the oxygen, and LiOH cylinders which absorb leftover CO₂.
Estimated deliverable payload weight is up to 200 kg and up to 65 kg can be returned.

The vehicle is protected during launch by a nose fairing with a launch escape system, which is jettisoned after passing through the atmosphere. The spacecraft is highly automated, and its Kurs system is capable of navigating to an automatic docking at the ISS. However, a pilot can operate the spacecraft independently of ground control if necessary.

Orbital module

The forward-most section of the spacecraft is the orbital module (), also referred to as the habitation module. It provides living space for the crew while in orbit, being more spacious than the confined reentry module, and includes a toilet.

There are three entry/exit ports: a forward port used for docking with the ISS; a side port used for crew access during ground operations; and an aft port that connects to the reentry module. In theory the side port could be used for a spacewalk, by closing the other two hatches and turning the entire module into an airlock; however this feature has never been used, because the ISS provides larger dedicated airlocks.

In zero gravity, the module's conceptual orientation differs from the reentry module's, with cosmonauts standing or sitting with their heads toward the forward docking port. There is a small forward-facing window, which allows the flight engineer to assist the commander with manual docking if automated systems fail.

The module can hold over of cargo during launch. Because this module is jettisoned before reentry and subsequently burns up in the atmosphere, it is typically packed with up to of waste before being sealed off.

The design of the orbital modules allows it to be customized for specific missions without affecting the safety-critical systems of the reentry module. Compared to previous Soyuz versions, the orbital module has additional anti-meteoroid shielding.

Descent module

The mid-section of the spacecraft is the reentry module (). It is where the crew is seated for launch and the journey back to Earth. It is covered by a heat-resistant covering to protect it during re-entry. It is slowed initially by the atmosphere, then by a braking parachute, followed by the main parachute, which slows the craft for landing. At one meter above the ground, solid-fuel braking engines mounted behind the heat shield are fired to give a soft landing. One of the design requirements for the reentry module was for it to have the highest possible volumetric efficiency (internal volume divided by hull area). The best shape for this is a sphere, but such a shape can provide no lift, which results in a purely ballistic reentry. Ballistic reentries are hard on the occupants due to high deceleration and can't be steered beyond their initial deorbit burn. That is why it was decided to go with the "headlight" shape that the Soyuz uses — a hemispherical forward area joined by a barely angled conical section (seven degrees) to a classic spherical section heat shield. This shape generates a small amount of lift due to the unequal weight distribution. The nickname was coined when nearly every automobile headlight was a circular paraboloid.

Instrumentation/propulsion module

The aft-most section of the spacecraft is the instrumentation/propulsion module (), also referred to as the service module or aggregate compartment. It is subdivided into three main sections: the intermediate compartment, the instrumentation compartment, and the propulsion compartment.

The instrumentation compartment (), is a pressurized container shaped like a bulging can that contains systems for temperature control, electric power supply, long-range communications, telemetry, and instruments for orientation and control. The propulsion compartment (), a non-pressurized part of the service module, contains the main engine and a spare: liquid-fuel propulsion systems for maneuvering in orbit and initiating the descent back to Earth. The spacecraft also has a system of low-thrust engines for orientation, attached to the intermediate compartment (). Outside the service module are the sensors for the orientation system and the solar array, which is oriented towards the sun by rotating the spacecraft.

Re-entry procedure

Because its modular construction differs from that of previous designs, the Soyuz has an unusual sequence of events prior to re-entry. The spacecraft is turned engine-forward and the main engine is fired for de-orbiting fully 180° ahead of its planned landing site. This requires the least propellant for re-entry, the spacecraft traveling on an elliptical Hohmann orbit to a point where it will be low enough in the atmosphere to re-enter.

Early Soyuz spacecraft would then have the service and orbital modules detach simultaneously. As they are connected by tubing and electrical cables to the descent module, this would aid in their separation and avoid having the descent module alter its orientation. Later, the Soyuz spacecraft detaches the orbital module before firing the main engine, which saves even more propellant and enables the descent module to return more payload. The orbital module cannot remain in orbit as an addition to a space station, as the hatch, which enables it to function as an airlock, is part of the descent module.

The parachute system is activated at an altitude of about . Two pilot parachutes deploy first, followed by a drogue chute that slows the spacecraft from . The main parachute then deploys, further reducing the descent rate to . The heat shield is jettisoned at an altitude of about , revealing six solid-propellant soft-landing motors that fire just above the ground, slowing the descent rate to less than . The seats inside the descent module, which are fitted with shock absorbers and liners custom molded to each crew member's body shape, cushion the final impact.

Soyuz missions typically land in the evening so that recovery helicopters can more easily see the spacecraft as it descends in the twilight, illuminated by the sun when it is above the shadow of the Earth. Since the beginning of Soyuz missions to the ISS, only five have performed nighttime landings.

Soyuz MS improvements

The Soyuz MS received the following upgrades with respect to the Soyuz TMA-M:

* Apparatus for Satellite Navigation (ASN-K, ): Instead of relying on six ground stations to determine its orbital path, the new ASN-K will use GLONASS and GPS signals. Compared to the prior system, ASN-K is far less bulky and can be used to locate the Soyuz descent capsule on the ground after landing. It uses four fixed antennas to achieve a positioning accuracy of and aims to reduce that number to as little as and to achieve an attitude accuracy of 0.5°.
* New Kurs-NA rendezvous system: The new Kurs-NA () automatic docking system is designed and manufactured in Russia, replacing its Ukrainian predecessor. This change addresses a political problem (with the two countries at war) and enhances the system’s capabilities with a higher level of computerization. While the original Kurs system was highly reliable over the years, many of its electronic components have become outdated. The Kurs-NA is lighter, 30% smaller, and consumes 25% less power. Additionally, it features a single phased-array antenna, replacing four antennas on the older system, while the two narrow-angle antennas have been retained although re-positioned further toward the rear. To assist with docking, the old halogen headlight has been replaced with a brighter, more energy-efficient LED light.
* Unified Command and Telemetry System (EKTS, ): Instead of solely relying on ground stations in Russian territory, the spacecraft has a satellite-capable communications system, EKTS, that connects to Russia's Luch system, providing coverage 83 percent of the day. It also retains very high frequency (VHF) and ultra high frequency (UHF) radios for communications with ground stations. The large EKTS S-band satellite antenna array, one of the most prominent new features on the ship's exterior, is also capable of communicating via American TDRS and Europe's EDRS satellites. The EKTS integrates several previous systems, including the BRTS (radio), MBITS (telemetry), and Rassvet (radio voice), which have been replaced or upgraded for compatibility. Additionally, it features a COSPAS-SARSAT transponder for real-time location tracking during reentry and landing. These changes enable the Soyuz to use the same ground segment terminals as the Russian Segment of the ISS.
* Re-arranged attitude control thrusters: the Integrated Propulsion System () was reconfigured provide full redundancy between two independent propellant manifold loops, supplying oxidizer and fuel to 14 pairs of high-thrust attitude control engines (eight pairs of large and six pairs of small thrusters). With each thruster pair connected to a different manifold, this arrangement significantly enhanced system reliability. Additionally, the number of aft-facing thrusters was doubled, providing crucial backup in case of main engine failure. To complement these hardware modifications, the avionics unit was redesigned, and the EFIR, responsible for tracking propellant consumption, was redesigned to prevent inaccurate readings.
* Improved docking mechanism: The docking system received a backup electric driving mechanism.
* SZI-M reusable black box: A new black box, the SZI-M () black box is installed beneath the commander's seat in the descent module. Designed and manufactured in Russia, this device records voice and data throughout the mission. With a capacity of 4 GB and a recording speed of 256 Kb/s, the SZI-M is designed to withstand extreme conditions. It can tolerate falls of 150 m/s and temperatures of 700°C for 30 minutes and is rated for 100,000 overwrite cycles. It can be reused on up to ten missions.
* Power system improvements: To support the increased energy consumption from the improved electronics, a fifth battery with a 155 amp-hour capacity was added, and the cell efficiency on the solar panels improved to 14% (from 12%), and the collective area increased by .
* Additional micro-meteoroid protection: Additional anti-micro-meteoroid shielding was added to the habitation module walls, largely at NASA's request. This measure was designed to safeguard the spacecraft's most vulnerable component against the unlikely but potential threat of a meteoroid or space debris impact.
* Digital camera system: The spacecraft utilizes a digital television camera system based on MPEG-2, replacing the older analog system. This upgrade enables space-to-space RF communication between the spacecraft and the station and reduces interference.

List of flights

References

External links

www.russianspaceweb.com – The Soyuz MS spacecraft

{{Russian human spaceflight programs

Crewed spacecraft
Soyuz program
Vehicles introduced in 2016