Soyuz-5 (Irtysh, Sunkar)

Soyuz-5 (GMM) [JSC RCC Progress]

Soyuz-5 [JSC RCC Progress]

Soyuz-5 [JSC RCC Progress]

Soyuz-5 is a medium-lift launch vehicle developed by Roscosmos (Russia), designed to replace the capabilities of the Zenit rocket family and partially substitute the cancelled Proton Medium/Light variants while also serving as a potential booster for future super-heavy launch systems.

The Soyuz-5 program aims to restore launch capabilities lost after the retirement of Zenit, particularly for missions from Baikonur Cosmodrome. It is designed for flexibility, supporting low Earth orbit (LEO) missions initially, with an optional upper stage enabling geostationary missions. Compatibility with existing Zenit infrastructure, including Site 45/1 at Baikonur, reduces development cost and complexity.

The rocket leverages heritage technologies and manufacturing infrastructure from earlier Soviet and Russian launch systems. Its 4.1 m diameter tanks allow reuse of tooling from the Proton rocket program while increasing propellant capacity compared to Zenit’s narrower 3.9 m tanks. The use of RP-1/LOX propellant represents a shift toward more environmentally acceptable fuels compared to Proton’s hypergolic propellants, aligning with requirements set by Kazakhstan for Baikonur operations.

Soyuz-5 is initially configured as a two-stage vehicle. The first stage, measuring 37.14 m in height, is powered by a single RD-171MV engine, an evolution of the RD-171M used on Zenit rockets. It carries approximately 363 tonnes of propellant and retains a 3.68 m aft section to maintain compatibility with existing launch infrastructure.

The second stage has a length of 7.77 m and the same 4.1 m diameter, with a dry mass of 5.9 tonnes and a propellant load of 59 tonnes of RG-1/LOX. It is powered by the RD-0124MS engine, offering improved efficiency over earlier designs.

The vehicle has a total launch mass of approximately 484 t. From Baikonur, Soyuz-5 is expected to deliver up to 16 t to a 200 km circular orbit at 51.6° inclination, significantly improving upon Zenit’s ~12 t capability.

For geostationary missions, Soyuz-5 can be equipped with the Blok DM-03 third stage. This stage, already used on vehicles such as Zenit-3SL and Angara A5, reduces development risk due to its operational heritage. With this configuration, Soyuz-5 is expected to deliver approximately 4.5 t to geostationary transfer orbit (GTO) and 2.3 t to geostationary orbit (GSO), improving on Zenit-3SLB performance.

The maiden flight of Soyuz-5 is planned for late March 2026 from Baikonur Cosmodrome.