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First stage forms classic shape of Soyuz
All rockets in the Soyuz family inherited their first and second stages from the original Soviet ICBM -- R-7. The four boosters of the first stage are clustered around a single central booster acting as the second stage.
The first stage of the R-7 ICBM consisted of four boosters.
Known specifications of a booster for the first stage of the Soyuz-2 rocket:
One of a kind architecture
Each of the four boosters, jokingly known as "markovkas" (carrots), of the first stage on the Soyuz rocket are equipped with an RD-107 four-chamber engine, burning a mix of kerosene fuel and liquid oxygen oxidizer. Each booster also carries two smaller thrusters which can swivel along a single axis in order to steer the rocket in flight.
The cylindrical fuel tank is located above the propulsion section, followed by a cone-shape oxidizer tank. All four boosters of the first stage and the central core module of the second stage begin firing on the ground, lifting the rocket off the pad. However, the smaller first-stage boosters consume their propellant and separate just around 118 seconds after liftoff at an altitude of around 48 kilometers, while the much larger second stage continues firing. At the time of the separation, the boosters have a speed of around 1.8 kilometers per second.
Boosters of the first stage for a Soyuz rocket in Vostochny circa November 2018.
Ignition of the first stage during the launch of the Progress-MS spacecraft in December 2015.
In April 2014, during the launch of the Sentinel-1A satellite from French Guiana, the Soyuz-2 rocket carried two pairs of cameras, which provided a dramatic close up view of the launch and stage separation for this type of rocket for the first time. A ground view of a separation between the first and second stage of the Soyuz rocket during the launch of the Sentinel-1A satellite on April 3, 2014.
Next chapter: Soyuz-1 launch vehicle
A separation sequence between strap-on boosters and the core stage of the R-7 rocket. Click to enlarge. A: Severing of lower connections, as all stages are still thrusting and pivoting of strap-on boosters around upper connectors. B: Upon reaching a certain rotation angle, upper connectors disengage, releasing boosters; oxidizer pressure valves open on boosters for retro thrust. V: Boosters fall away from the core stage, which continues a powered flight. Credit: Moscow Aviation Institute
In April 2014, during the launch of the Sentinel-1A satellite from French Guiana, the Soyuz-2 rocket carried two pairs of cameras, which provided first ever close-up view of the launch and stage separation for this historic rocket. Credit: Arianespace
A wooden ignition bar, PZU, for the first stage of the Soyuz rocket.