The RD -120 ( двигатель of Russian Реактивный, " Reaktiwnyj Dwigatel " German rocket engine, GREY index 11D123 ) is a rocket engine for liquid rocket. It should not be confused with the RD -0120 ( 11D122 ) of the Energia rocket, which reached a much higher thrust.

Development and use

The RD -120 was developed by the Soviet chief designer Valentin Glushko rocket engines during the period 1976-1985 at the Leningrad gas dynamic laboratory and is now marketed by NPO Energomash. An RD -120 is used in the Zenit rocket as a drive for the second stage of the rocket and is optimized to operate in a vacuum. The first flight took place in 1985 and until 2006 60 pieces were used. Although the RD -120 developed significantly less thrust than the Erststufentriebwerk RD -171, it was involved in most of the false starts: nine false starts accounted for six of the failure of the second stage. Since 2003, the Zenit 3SL comes to one developed from 2001 version of the engine with 10% more thrust for use.


RD -120 is operated with fuel and liquid oxygen (LOX ), and comprises a preliminary and a main combustion chamber, a turbine and a gas generator. It is supported by an additional engine of the RD -8 with four swiveling by 33 ° thrusters for attitude control.

Another special feature of the engine is that the power can be reduced to 80 % in order to reduce the burden on the missile structure shortly before the end of firing. Similar to the RD -253, the turbine arranged to drive the fuel pump within the precombustion chamber ( closed circuit). To the total amount of oxidant and a small amount of fuel is supplied, which burns there with a low temperature and the turbine. The exhaust gas then passes from the combustion prechamber to the main combustion chamber where the main part of the fuel is fed and burns. By this design, the engine no drive gas for the pump is also lost in the huge chamber pressure of about 160 bar.

As RD- 120K (also called RD -123 ) and RD- 120M are two variants of the RD -120 engine designated, which are adapted for operation at sea level and so can serve as Erststufentriebwerk. They have an order of 6 ° swiveling and shortened in two planes nozzle. Development began around 1994 and the prototype of the RD- 120K has been tested since 1996, but both versions never reached mass production ..