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RD-108

RD-107
RD-107 Vostok.jpg
Rocket engine RD-107 "Vostok" in the Museum of Space and Missile Technology (Saint Petersburg).
Country of origin  Soviet Union
Designer OKB-456
Manufacturer JSC Kuznetsov
Application booster engine
Associated L/V R-7 Family of launchers
Predecessor RD-105
Status In Production
Liquid-fuel engine
Propellant LOX / Kerosene
Cycle Gas generator
Performance
Thrust (vac.) RD-107: 1,000 kN (220,000 lbf)
RD-107A: 1,020 kN (230,000 lbf)
Thrust (SL) RD-107: 810 kN (180,000 lbf)
RD-107A: 839 kN (189,000 lbf)
Isp (vac.) RD-107: 313 sec
RD-107A: 320.2 sec
Isp (SL) RD-107: 256 sec
RD-107A: 263.3 sec
Dimensions
Dry weight RD-107: 1,190 kg (2,620 lb)
RD-107A1,190 kg (2,620 lb)
Used in
First stage boosters for R-7 family
References
References

The RD-107 and its sibling, the RD-108, are a type of rocket engine initially used to launch R-7 Semyorka missiles. RD-107 engines were later used on space launch vehicles based on the R-7. As of 2015, very similar RD-107A and RD-108A engines are used to launch the Soyuz FG, Soyuz-2.1a and Soyuz-2.1b, which are in active service.

The RD-107 was designed under the direction of Valentin Glushko at the Gas Dynamics Laboratory-Experimental Design Bureau (OKB-456) between 1954 and 1957. It uses liquid oxygen and kerosene as propellants, operating in a gas generator cycle. As was typical by all the descendants of the V-2 rocket technology, the turbine is driven by steam generated by catalytic decomposition of H2O2. The steam generator uses solid F-30-P-G catalyst. These are based on variable sized pellet covered in an aqueous solution of potassium permanganate and sodium as active catalyst. Each engine uses four fixed main combustion chambers. The RD-107 has an additional two vernier combustion chambers that can gimbal in a single plane, to supply thrust vectoring. The RD-108 has four of such vernier combustion chambers to supply full vector control to the Blok-A stage. The single-axle turbopump unit includes the steam driven turbine, an oxidizer pump, a fuel pump, and a nitrogen gas generator for tank pressurization.

One important innovation of this engine was the capability to use variable mixture ratio between fuel and oxidizer. The natural variations in manufacturing between each engine meant that without an active propellant consumption control, each boosters would deplete oxygen and fuel at different rates. This might result in as much as tens of tonnes of propellant near the end of their burn. It would generate enormous strains on the structure and control authority due to the mass imbalance. Thus, the engines and the control system was developed to ensure the simultaneous consumption of propellant mass among the four R-7 boosters.


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