Soyuz 2.1a Progress-MS [RSS]

Soyuz 2.1a

The Soyuz 2.1a incorporates upgraded RD-107A engines in the first stage (the four boosters) and the upgraded RD-108A engine in the second stage (the central core). The engines have improved injection systems to enhance overall performance.

The 2.1a also has a digital flight control system, replacing the analog system used on prior Soyuz models. This system allows the vehicle to adjust its trajectory in-flight (a capability the analog system lacked) eliminating the requirement for a complex rotating launchpad.

The digital flight control system also unlocks the potential for deploying larger commercial satellites housed within wider and longer payload fairings. These fairings introduced too much aerodynamic instability for the old analog system to handle. When configured with this larger ST payload fairing, the Soyuz 2.1a is sometimes called Soyuz ST-A.

Progress-MS

The Progress spacecraft’s uncrewed and disposable design enables significant weight reduction. Unlike Soyuz, it does not require life support systems, heat shields, parachutes, or automatic crew rescue systems. Additionally, it lacks the ability to separate into multiple modules. after completing its mission, the spacecraft undocks, performs a controlled retrofire, and burns up upon reentry into Earth's atmosphere.

The descent module was replaced with a unpressurized refuel compartiment. After docking, the propellant tanks of the station and refueling tanks onboard the cargo ship would be linked up via docking port and make it possible to pump propellant back and forth.

The unpressurized fuel compartiment also have a total of 420 liters of water to be delivered to the station.

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