Soyuz: the world’s most reliable human spacecraft

Out of all the human spacecrafts, I am most nostalgic for two human space ferries of my time—the American Space Shuttle and the Russian Soyuz spacecraft. I grew up reading about them, dreaming about them, drawing them, as well as making scaled models of them while in high school. My Sanskrit teacher presented me with the book Aboard the Space Shuttle, published in the 1980s, by the NASA headquarters in Washington DC. She had brought this copy with her from the United States, when her husband worked at NASA. This book marked both my introduction and interest in human space ferries.

Many years later, after post graduation, in 1997, I went to work on Shuttle-Mir missions, while on a professional placement at NASA's Johnson Space Center. The NASA stint was a dream come true—thrilling and joyous—because two of my favourite human spacecrafts became real, operational, orbital crafts that flew in space missions that I got to work on. Those were super exciting times for a young engineer-designer exploring the world of space, human factors and habitability, among other things.

Soyuz—the-rocket, and Soyuz—the-spacecraft

For those not familiar with the Soyuz fleet, it perhaps makes sense to clarify that there are two types of Soyuz—the first is a family of expendable Russian and Soviet carrier rockets developed by OKB and manufactured by Progress Rocket Centre in Samara, Russia. Soyuz also happens to be a series of spacecraft, which have been flying since their debut, in 1967. Soyuz, the rocket, is the most frequently used launch vehicle in the world (if you ask me, one of the most beautiful rockets in the world fleet), and as of 2021, has made 1900 flights since its debut in 1966.

Soyuz, the spacecraft,¹ is the world’s safest, most reliable, most cost-effective human spaceflight vehicle², established by its unparalleled length of operational history. Soyuz spacecraft were used to carry cosmonauts to and from Salyut and later Mir space stations.

Since 1998, Soyuz had been used for transport—to and from the orbiting International Space Station (ISS) and post summer of 2011, when NASA retired its Space Shuttle fleet, for the next nine years, until SpaceX’s Crew Dragon made its debut in May 2020, Soyuz was the only human ferry keeping the ISS³ afloat and crewed at all times. This narrative is about Soyuz, the spacecraft.

The Soyuz rocket lift-off

The Soyuz capsule launches on top of the Soyuz rocket from Kazakhstan, a country on Russia’s southern border. It takes about nine minutes to reach space.

After the launch, the capsule and rocket separate. The rocket returns to Earth, while the capsule goes and docks with the ISS. The Soyuz capsule takes about six hours to get to the space station and at least one Soyuz spacecraft is docked to the ISS, at all times, as an escape craft in the event of an emergency. The crew uses the hatch on the Soyuz to enter and leave the station and when the crew is ready to come home, they ride in the Soyuz capsule back to Earth. To land, the Soyuz drops through Earth's atmosphere. The atmosphere slows the Soyuz and it further uses parachutes to slow down more. When the Soyuz gets close to the ground, it fires small rocket engines to slow down more, after which it lands in the grassy plains of Kazakhstan. After leaving the space station, the Soyuz takes about three and a half hours to land.⁴

A look into Soyuz-TMA capsule architecture⁵

The Soyuz spacecraft has undergone a series of upgrades since 1967. The latest variant—Soyuz TMA spacecraft, is a replacement for the Soyuz TM, which was used from 1986 to 2002, to take astronauts and cosmonauts to Mir and then to ISS. The Soyuz TMA debuted in 2002 with a crewed flight to the ISS. Its design incorporated changes to meet certain NASA requirements as an ISS ‘lifeboat’—including eased height and weight restrictions for crew members.⁶

Compared to the Soyuz TM, Soyuz TMA has increased safety, especially in descent and landing. It has smaller and more efficient computers and improved displays. In addition, the Soyuz TMA accommodates individuals as large as 1.9 metres (6 feet, 3 inches tall) and 95 kilograms (209 pounds), compared to 1.8 metres (6 feet) and 85 kilograms (187 pounds) in the earlier TM. The two new engines reduce landing speed and the force felt by crew members, by 15 to 30 per cent. With the new entry control system and three-axis accelerometer increasing landing accuracy.

Instrumentation improvements also include a colour ‘glass cockpit,’ which is easier to use and gives the crew more information, with hand controllers that can be secured under an instrument panel. All new components in the Soyuz TMA can spend up to one year in space. The new components as well as the entire TMA were rigorously tested on the ground, in hangar-drop tests, in airdrop tests and in space, before the spacecraft was declared flight-ready. While Descent Module structural modifications, seats and seat shock absorbers were tested in hangar drop tests, the landing system modifications, including associated software upgrades, were tested in a series of airdrop tests.⁷

The Soyuz capsule has three parts, also known as modules⁸—the first part of the capsule is the ‘Orbital Module.’ While they are in orbit, crew members live in the Orbital Module, that is about the size of a large van. The Orbital Module can connect to the space station and is known as the habitation section. It houses all the equipment that is not needed for re-entry, such as experiments, cameras or cargo. The module also contains a toilet, docking avionics and communications gear. On the latest Soyuz variant, the Soyuz TM, a small window was also introduced, providing the crew with a front view.

The second part of the capsule, the ‘Descent Module,’ also known as the ‘Re-entry Capsule,’ is used both for launch and the journey back to earth. The crew sits in this part when the Soyuz is launching to the space station. Half of the Descent Module is covered by a heat-resistant covering, protecting it during re-entry; this half faces forward 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 metre above the ground, solid-fuel braking engines, mounted behind the heat shield, are fired to give a soft landing.

A hatch between the Orbital Module and the Descent Module can be closed, isolating it to act as an airlock if needed, with crew members exiting through its side port (near the Descent Module). On the launch pad, the crew enter the spacecraft through this port. This separation also allows the Orbital Module to be customised according to the mission, with less risk to the life-critical Descent Module, allowing for a safe landing. Without separation of the Orbital Module, it is not possible for the crew to survive landing in the Descent Module. This is because the Orbital Module would interfere with the proper deployment of the Descent Module's parachutes, with the extra mass exceeding the capability of the main parachute and braking engines to provide a safe soft-landing speed.

The third module is the 'Instrumentation and Propulsion Module' or the 'Service Module.' It has a pressurised container, shaped like a bulging can (instrumentation compartment, priborniy otsek) that contains systems for temperature control, electric power supply, long-range radio communications, radio telemetry and instruments for orientation and control. A non-pressurised part of the Service Module (propulsion compartment, agregatniy otsek) contains the main engine and a liquid-fuelled propulsion system for manoeuvring in the orbit and initiating the descent back to Earth. The ship also has a system of low-thrust engines for orientation, attached to the intermediate compartment (perekhodnoi otsek). Outside the Service Module are sensors for the orientation system and the solar array, which is oriented towards the sun, by rotating the ship.

The Return-to-Earth Choreography

Now, let us visualise the Soyuz undocking, re-entry, and landing via this ESA video:

Next, let us take a closer look at the ISS Expedition-39 crew's return⁹ in May 2014, to know the Soyuz a little more intimately. The Expedition 39 crew returned to the Earth after 188 days in space, completing a journey of over 79 million miles (127 million km) and after more than 3,000 orbits of the Earth, since launching to the ISS in November 2013.

The Soyuz TMA-11M spacecraft carrying Expedition 39 Commander Koichi Wakata of the Japan Aerospace Exploration Agency (JAXA), Soyuz Commander Mikhail Tyurin of Roscosmos, the Russian Federal Space Agency and Flight Engineer Rick Mastracchio of NASA, undocked from the Rassvet module on the Earth-facing side of the station at 6:36 p.m. EST, as the station soared 261 statute miles (420 km) over Mongolia.

The four minute, 41-second deorbit burn began at 9:04 pm EST, slowing the Soyuz for its descent into Earth’s atmosphere and for its parachute-assisted landing.

The Soyuz landed in the steppe of Kazakhstan at 9:58 pm EST (7:58 am, Wednesday, Kazakh time). The helicopters carrying the Russian recovery teams and NASA personnels reached the landing site shortly afterwards, to assist the crew and conduct medical examinations.

The Future

Soyuz TMA continues to service the ISS, humanity’s largest orbital outpost, built with the cooperation of 16 nations, and led by Russia and the United States. 

The ISS is entering a transition period, as NASA is encouraging the development of private space stations in Earth’s orbit. NASA released a report in February 2022, outlining big-picture goals for the orbiting lab's operational life, expected to end with a controlled deorbit in January 2031. NASA confirmed through their new transition plan that ISS will continue its service until 2030, and will then be plunged into an uninhabited area of the Pacific Ocean in January 2031.¹⁰

NASA has now embarked on a new human lunar exploration program called Artemis¹¹ and plans to collaborate with commercial and international partners to establish long-term presence on the moon. In March 2021, China and Russia, too, announced that they are teaming up on an ambitious project called the 'International Lunar Research Station (ILRS).' The two space powers hope to build a moon base together, by the mid-2030s.¹²

References

^1.https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-the-soyuz-spacecraft-k-4
^2.https://www.nbcnews.com/id/wbna9509254
^3.https://www.nasa.gov/mission_pages/station/main/index.html
^4.https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-the-soyuz-spacecraft-k-4
^5.https://en.wikipedia.org/wiki/Soyuz_(spacecraft)
^6.https://www.britannica.com/technology/Soyuz
^7.https://www.nasa.gov/pdf/135404main_exp12_presskit.pdf
^8.https://en.wikipedia.org/wiki/Soyuz_(spacecraft)
^9.https://www.nasa.gov/content/expedition-39-crew-returns-to-earth-after-six-months-on-station
^10.https://www.space.com/nasa-international-space-station-plan-final-years-2030
^11.https://www.nasa.gov/specials/artemis/
^12.https://www.space.com/china-russia-moon-base-ilrs