Soyuz-2

Soyuz 2.1a

The key advancement of the Soyuz‑2.1a is its digital flight control system, replacing the analog unit used in previous Soyuz models.^[2] 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.^[15]

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.^[16] 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 5-second (0.049 km/s) 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.^[2][17][18]

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 300 kilograms (660 lb).^[3][19][2]

The Soyuz‑2.1a conducted its maiden flight on 8 November 2004, launching from Plesetsk Cosmodrome Site 43 with a boilerplate payload simulating a Zenit-8 spy satellite.^[2]

Soyuz 2.1b

The Soyuz 2.1b 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 326 to 359 seconds (3.20 to 3.52 km/s). Although maximum thrust was slightly reduced from 298 to 294 kilonewtons (67,000 to 66,000 lb_f), 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 7,430 kilograms (16,380 lb) to 8,670 kilograms (19,110 lb), when compared to the 2.1a.^[20][21]

The first launch of a Soyuz‑2.1b occurred from Plesetsk Cosmodrome Site 43 on 26 July 2008 with a classified military payload.^[22]

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  Closeup of booster and core stage engines of a Soyuz‑2.1a during launch
• 
  Soyuz‑2.1a prepared for human spaceflight mission Soyuz MS-26
• 
  Soyuz‑2.1b prepared for GLONASS-K2 satellite launch
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  From left to right: Soyuz‑2.1v, Soyuz‑2.1b, Soyuz‑2.1a (crewed variant) and the proposed Soyuz‑5

Suborbital test flight

On 8 November 2004, at 18:30 UTC, the first Soyuz‑2 rocket, in the Soyuz‑2.1a 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 Soyuz‑2 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 Soyuz‑2 took place on 9 April 2020, carrying Soyuz MS-16 to the ISS.

Naphthyl fuel

Following successful ground testing, a naphthyl (Russian: нафтил) fueled Soyuz‑2.1b 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.^[30]

Planned launches

This list is incomplete; you can help by adding missing items. (August 2021)