Soyuz 2.1a

Soyuz2 (; GRAU index: 14A14) is a Russian expendable medium-lift launch vehicle and the seventh major iteration of the Soyuz rocket family. Compared to its predecessors, Soyuz-2 features significant upgrades, including improved engines and a digital flight control system that enables launches from fixed platforms and supports larger payload fairings.

Developed by the Progress Rocket Space Centre (RKTs Progress) in Samara, Soyuz-2 is used to place payloads into low Earth orbit in standard configuration but can also support missions to higher orbits using an additional upper stage, most commonly the Fregat, though the smaller Volga is available as a less expensive option. Since its introduction in 2004, Soyuz-2 has gradually replaced earlier Soyuz variants and is launched from the facilities of its R-7 derived predecessors: Site 31/6 at the Baikonur Cosmodrome in Kazakhstan and Sites 43/3 and 43/4 at the Plesetsk Cosmodrome in northwestern Russia, and, since 2016, Site 1S at the Vostochny Cosmodrome in eastern Russia.

The Soyuz2 family includes several variants. The base model, Soyuz2.1a, debuted on 8 November 2004, followed by the Soyuz2.1b, with a 15 percent more powerful third stage, on 27 December 2006. A derivative version, SoyuzST, was introduced in 2011 with modifications for operation at the Guiana Space Centre, the European Space Agency's launch site in French Guiana. Launches from this site were suspended in 2022 following the Russian invasion of Ukraine.

History

The Soyuz-2 project was launched by RKTs Progress with support from the Russian government in the early 1990s as the "Rus" program. In the aftermath of the collapse of the Soviet Union, the program aimed to consolidate the launch vehicle's subcontractor network within the Russian Federation and transition to fully domestic production. The project evolved into Soyuz-2, introducing technical upgrades to replace the aging Soyuz-U (in service since 1973) and Molniya-M (in service since 1965). These earlier models relied on an analog guidance, navigation, and control systems developed in the 1960s by a Ukrainian firm, the Polisvit Special Design Bureau. The modernization effort also included engine upgrades, allowing for improved performance through newer, more powerful designs.

The Soyuz-2 upgrades included a fully digital flight control system, modernized RD-107A and RD-108A engines with an improved injection system for the boosters and core stage, and a new RD-0124 third-stage engine engine using oxygen-rich staged combustion. These enhancements aimed to increase payload capacity by approximately .

Development of the digital control system began in 1993 at NPO Avtomatiki in Yekaterinburg.The new system featured three redundant processing units and dual gyroscopes, significantly improving reliability. According to NPO Avtomatiki's deputy director, participation in the Soyuz-2 program helped save the company.

However, progress slowed during the financial crisis facing the Russian space industry in the late 1990s and early 2000s. As a result, the upgrade plan was divided into phases. The RD-107A and RD-108A engines were introduced early as part of the Soyuz-FG, a transitional design based on the Soyuz-U. The majority of design changes were incorporated into the Soyuz-2.1a, while development of the RD-0124 was delayed and eventually implemented on the Soyuz-2.1b.

Soyuz-2.1a conducted its first suborbital test from the Plesetsk Cosmodrome on 8 November 2004. It made its first operational flight in October 2006, successfully launching the MetOp-A satellite for ESA and EUMETSAT. The Soyuz-2.1b, equipped with the new third-stage, debuted on 27 December 2006. Over time, the Soyuz-2 family replaced its predecessors: Molniya-M in 2010, Soyuz-U in 2017, and Soyuz-FG in 2019.

Variants

Soyuz 2.1a

The key advancement of the Soyuz2.1a is its digital flight control system, replacing the analog unit used in previous Soyuz models. The digital system supports enabled mid-flight trajectory adjustments, eliminating the need for rotating launch pads. The system also allows the use of larger payload fairings, enabling the launch of heavier commercial satellites that the analog system could not handle due to the aerodynamic instability the fairings generate.

The rocket uses upgraded RD-107A (boosters) and RD-108A (core) engines, developed for Soyuz-2 but first flown on Soyuz-FG, as their development outpaced the rocket's other upgrades. These engines feature over 1,000 single-component injectors, replacing the older 260 dual-component centrifugal injectors in the earlier RD-107/RD-108, resulting in more efficient combustion and approximately a increase in specific impulse, a five percent improvement. Additionally, a chemical ignition system replaced the previous method that relied on placing wooden sticks with a pair of pyrotechnic charges in each combustion chamber.

The third stage retained the RD-0110 engine, which has flown on most Soyuz variants dating back to the 1960s, but adopted a revised tank structure, shared with Soyuz-2.1b, with slightly enlarged propellant tanks. When combined with the physically lighter and more capable digital flight control system, these changes raised the payload capacity by about .

The Soyuz2.1a conducted its maiden flight on 8 November 2004, launching from Plesetsk Cosmodrome Site 43 with a boilerplate payload simulating a Zenit-8 spy satellite.

Soyuz 2.1b

The Soyuz2.1b retains all upgrades of the 2.1a and introduces a new third stage powered by the RD-0124 engine. Utilizing oxygen-rich staged combustion, the engine increases specific impulse from . Although maximum thrust was slightly reduced from , the burn time was extended by 20 seconds using the same fuel load, resulting in improved overall performance.

This new third stage significantly improved payload capacity. For example, payload capacity to low Earth orbit from the Baikonur Cosmodrome increased from approximately to , when compared to the 2.1a.

The first launch of a Soyuz2.1b occurred from Plesetsk Cosmodrome Site 43 on 26 July 2008 with a classified military payload.

File:Expedition 72 Launch (NHQ202409110009).jpg, Closeup of booster and core stage engines of a Soyuz2.1a during launch
File:Expedition 72 Soyuz Rollout (NHQ202409080028).jpg, Soyuz2.1a prepared for human spaceflight mission Soyuz MS-26
File:Soyuz 2.1b GLONASS-K2 13L launch 04.jpg, Soyuz2.1b prepared for GLONASS-K2 satellite launch
File:"Soyuz" launch vehicles model series on MAKS-2021.jpg, From left to right: Soyuz2.1v, Soyuz2.1b, Soyuz2.1a (crewed variant) and the proposed Soyuz5

Vostochny modifications

The Soyuz-2 family received specific modifications for operation from the Vostochny Cosmodrome, aimed at improving reliability, compatibility with ground infrastructure, and safety:

* Enhanced Durability: The rocket was modified to remain fueled on the launch pad for up to 100 hours and withstand transport over distances of up to from the manufacturing site in Samara to the Russian Far East.
* Adaptation for Vertical Integration: Structural and piping modifications enable vertical payload integration and safely vent excess propellant outside the Mobile Service Tower, minimizing oxygen vapor buildup inside the gantry.
* Upgraded Computer: Offers six times the performance, reduced weight, and simplified wiring through multiplexing and shared data buses.
* Improved Batteries: New nickel-cadmium batteries eliminate the need for a dedicated charging station.

On 1 October 2015, it was revealed that parts of the assembly complex at Vostochny had been incorrectly designed for a different rocket variant, with some structures too small to accommodate Soyuz-2. This issue cast doubt on the planned inaugural launch in December 2015. The first launch successfully took place on 28 April 2016.

Notable missions

Suborbital test flight

On 8 November 2004, at 18:30 UTC, the first Soyuz2 rocket, in the Soyuz2.1a configuration, was launched from the Plesetsk Cosmodrome in Russia. The rocket followed a suborbital trajectory, with the third stage and Boilerplate landing in the Pacific Ocean.

Maiden launch

The first attempt at launching a Soyuz2 to orbit with the MetOp-A satellite occurred on 17 July 2006. It was scrubbed two hours before the launch by an automatic sequence after the onboard computer failed to check the launch azimuth. Fuelling of the rocket was underway at the time, and all launch complex equipment and onboard preliminary checks had proceeded without incident. The rocket was left fuelled on the launch pad for the next attempt on 18 July 2006. Launch was eventually conducted on 19 October 2006.

First crewed mission

The first crewed launch of Soyuz2 took place on 9 April 2020, carrying Soyuz MS-16 to the ISS.

''Naphthyl'' fuel

Following successful ground testing, a ''naphthyl'' (Russian: нафтил) fueled Soyuz2.1b launch took place on 22 October 2022 at Vostochny. ''Naphthyl'' is an environmentally safe hydrocarbon fuel with fewer aromatic compounds than kerosene, which also slightly improves engine performance. There are only minor differences in thermal properties, viscosity, and surface tension, so this did not require significant engine changes.

Launch statistics

Since 2006, Soyuz2 rockets have accumulated a total of 150 launches, 145 of which were successful, yielding a success rate.

Launch outcomes

Launch sites

List of launches

Planned launches

See also

* Soyuz programme
* List of R-7 launches
* Medium-lift launch vehicle

Notes

References

External links

*

Encyclopedia Astronautica article on Soyuz 2.1



Soyuz User's Manual
from Starsem

Soyuz-2 launch vehicle
from Roscosmos

{{R-7 rockets

R-7 (rocket family)
Space launch vehicles of Russia
Vehicles introduced in 2004