Irtysh (rocket)

Irtysh (Иртыш), also named Soyuz-5 (Союз-5), formerly codenamed Fenix in Russian and Sunkar (Сұңқар) in Kazakh, is a planned Russian rocket that is being developed by JSC SRC Progress within the "Project Feniks" (Феникс). Initially it will replace the capability of Zenit-2 and Proton Medium, and in the future will serve as the base of a super heavy-lift launch vehicle rocket (Yenisei) to match the Energia/Buran capabilities. , Irtysh is expected to launch from the Baikonur Baiterek, the ex Zenit-2 launch site, in a partnership with the government of Kazakhstan, with a planned debut in December 2025.

Project organization
The current proposal is led by JSC SRC Progress, with support by Khrunichev and Makeyev, additionally, RSC Energia would handle the launch site, and supply the Blok DM-03, while Roscosmos would finance the development through the Project Fenicks under the 2016–2025 Russian space master plan. KazCosmos would also be a partner since the initial launch pad would be at Baikonur Cosmodrome Site 45 in Kazakhstan, within the framework of the Baiterek bi-national joint venture, and International Launch Services (ILS) would commercialize its services for the international market.

The initial application of the launch vehicle would be to cover the under 5 tonne to GTO commercial launch segment. With the loss of the Zenit-3SLB due to Russian conflicts with Ukraine, both the decision not to develop Angara A3 and launch Angara A5 from Vostochny, the Baiterek project was without a launch vehicle. The 2016 announcement of the Proton Medium and Light meant that ILS could enter the medium GTO launch market, but since the Kazakh government desired to deprecate the use of highly toxic hypergolic propellants used by Proton, they would need a replacement.

For this commercial application, JSC SRC Progress proposed the Soyuz-5 in early 2016. It would start with this commercial application with the prospect of also enabling a super heavy launcher with a 80 tonne payload capability to low Earth orbit. The Kazakh side agreed on the general terms, but the investment share was left to decide. As part of the 2016 arrangements, the Kazakh government would get ownership of one of the Proton launch pads, and participate in the operations of Proton-Medium and Proton-Light. Then, they would get to participate in the Irtysh launchers since its expected debut in 2024. As of August 2023 further delays in the construction of the launch site and in the development of the rocket pushed the date of the maiden flight to December 2025.

Four test launches are planned before the development is considered complete.

Development of the Irtysh is expected to face delays, as the necessary modification of the launch pad at Site 45 for launching the Irtysh has been delayed, starting only in late 2021. International sanctions following the Russian Invasion of Ukraine further slowed operations. In July 2022, Dmitry Rogozin, then CEO of Roscosmos, admitted that construction would be postponed by six months to one year.

In March 2023, it became public that the Baiterek Kazakh-Russian joint venture in charge of the site had seized the facility after filing a claim of about 2 billion rubles (30.3 million US-Dollar) to TsENKI, a Roscosmos subsidiary in charge of handling ground-based infrastructure, as Roscosmos had failed its obligation to conduct an environmental impact assessment of Site 45, causing additional delays.

Vehicle
Soyuz-5, as proposed in 2016, leverages existing propulsion and tooling, while enabling a platform that would replace the lost capabilities of the Zenit family, replace the Proton Light/Medium, and could serve as the boosters of a new super heavy rocket. It will initially be a two-stage rocket, but could be enhanced with an optional Blok DM-03 for geostationary missions. It would be compatible with most of the Zenit's ground infrastructure, and even use the Site 45 at Baikonur.

Its tanks would be 4.1 m in diameter, which would enable the re use of Proton tooling. Since they would be wider than Zenit, (3.9 m) it would enable a higher propellant load for the same height. While this diameter enables a heavier rocket and is already compatible with train transport to Baikonur, it would prevent that method of transport for Vostochny Cosmodrome. It would use the relatively environmental friendly RP-1/LOX propellant, which would be an improvement over the highly toxic hypergolics of Proton. This has been a requirement from the Kazakh government for new projects.

The first stage would be powered by an RD-171MV, very similar to the RD-171M used in Zenit 2 and 3. With a height of 37.14 m it would be higher than Zenit's first stage (32.94 m) and wider, and thus it could carry 363 tonne of propellant versus 290 tonne. Its base would still feature a 3.68 m aft section for compatibility with Zenit's pad and support infrastructure.

Its second stage would measure 7.77 m by 4.1 m in diameter, with a dry mass of 5.9 tonne and an RG-1/LOX load of 59 tonne. It would be powered by two RD-0124MS engines, each having four nozzles arranged in a semicircle. So, two engines would feature eight total nozzles close to the rocket perimeter, forming a circle. This arrangement would minimize the stage length, while keeping the engines' excellent specific impulse.

With a gross mass of 484 tonne against Zenit 430 tonne, and the improved efficiency of its second stage, it could launch 16 tonne to a 200 km circular orbit with an inclination of 51.6° to the Equator from Baikonur. This is a significant improvement over Zenit, which could only place roughly 12 tonne to the same orbit.

For geostationary launch missions, it could optionally be equipped with a Blok DM-03 third stage. Since it would use the same propellant and is already used on the Zenit-3SL and Angara A5, it would be a low risk option. The expected performance of 4.5 tonne to GTO and 2.3 tonne to GSO, it would improve over Zenit-3SLB 3.6 tonne and 1.59 tonne.

Soyuz-5 Super Heavy (Yenisei)
The Irtysh first stage could be used as the boosters (and even core) of the super heavy rocket Yenisei capable of launching 73 tonne to low Earth orbit from Baikonur or Vostochny. Improving the performance to 120 tonne and even 160 tonne was considered possible with this architecture. While the current 2016-2025 plan for deep space exploration calls for the use of the heavy Angara 5V, it would just enable 36 tonne, requiring up to four launches for a single Moon mission, and would also require the use of expensive hydrogen as fuel. The Yenisei would simplify the mission while using readily available Irtysh first stages.