Soyuz MS-17 | Soyuz 2.1a

Who are the Soyuz MS-17 crew?

Sergey Ryzhikov is the commander of flight MS-17, and will take over from Chris Cassidy as commander of the ISS. This is his second space flight. His previous spaceflight was to the ISS as part of Expedition 49/50.

Sergey Kud-Sverchkov is Flight Engineer 1 on this flight. This is his first flight into space.

Kathleen (Kate) Rubins is Flight Engineer 2 on this flight. This is her second space flight. Her previous flight was to the ISS as part of Expedition 48/49. So, she has shared time on board the ISS with Sergey Ryzhikov on their previous flights!

Under current NASA plans, this will be the last flight of a NASA astronaut that has been paid for with cash. Future NASA astronauts will only fly under equal ride sharing with Russian cosmonauts riding on NASA’s commercial crew flights in  exchange.

Sergey Ryzhikov (Credit: NASA / Bill Ingalls)

Sergey Kud-Sverchkov (Credit: NASA)

Kate Rubins (Credit: NASA / Josh Valcarcel)

What about the rocket?

Introduced in 1966, the Soyuz rocket (also known as R7) has been the workhorse of the Soviet/Russian space program. The first launch of the Soyuz 2-1a version on November 8, 2004 from the Plesetsk Cosmodrome represented a major step in the Soyuz launch vehicle’s development program.

The crewed Soyuz version currently offered by Russia is a three-stage launch vehicle, which consists of:

• four side boosters (booster)
• a central core (first stage)
• an upper central stage
• the Soyuz MS spacecraft itself

Side boosters

The side boosters’ RD-107A engines are powered by liquid oxygen and kerosene, which are the same propellants used on each of the rocket stages. The kerosene tanks are located in the cylindrical part and the liquid oxygen tanks in the conical section. Each engine has four combustion chambers and four nozzles.

During side booster separation, the boosters perform a well-known pattern, in which they peel off and cartwheel outwards! This is known as the “Korolev cross”, named after Sergei Korolev, the Chief Design Engineer of the USSR space program in the 1960s.

Center core

The center core is fitted with an RD-108A engine, and also has four combustion chambers and four nozzles. It also has four vernier thrusters, used for three-axis flight control once the side boosters have separated. The upper stage engine’s thrust enables the stage to separate directly from the central core. This is called “hot staging”.

Upper stage

The upper stage uses either an RD-0110 engine in the Soyuz ST-A (2-1a) version, or an RD-0124 engine in the ST-B (2-1b) version. This flight is using a 2.1a vehicle, so in this case the stage has an RD-0110 engine.

What about the spacecraft?

The Soyuz MS spacecraft is the latest version of Russia’s long-standing three-person spacecraft. Soyuz capsules first flew in the 1960s. The spacecraft external appearance is largely unchanged over this time. However, the internal systems and capabilities have been upgraded many times.

The Soyuz MS variant is one of the versions from the fourth generation of this spacecraft. Its first flight was in 2006. Soyuz consists of three sections:

• the orbital module
• the descent module
• the service module

The orbital module

This is the forward section of the spacecraft, the part that docks to the ISS. It is the part of the spacecraft where the crew will spend most of their time on orbit. It has more living room than the descent module. On the Progress uncrewed resupply missions, this is replaced by a cargo module.

The descent module

This is the middle section of the spacecraft. It is the only part that returns intact to Earth ground level. This is where the crew will sit during the launch and the reentry. They will be wearing spacesuits in case of capsule depressurization. There is very little room for the crew of three in this module. On the Progress uncrewed resupply missions, this is replaced by a refueling module that can transfer fuel into the Russian segment. This can then be used by thrusters on the ISS to boost its orbit.

The service module

This is the aft (rear) section of the spacecraft. It provides the main engine used for maneuvring on orbit and the thrusters for fine control during docking and departure. Also, it also contains the life support system for environmental control of the rest of the spacecraft. In addition, it also supports the solar panels and various radio communication systems.