RD-120

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

Development and use

The RD-120 was developed by the Soviet chief designer for rocket motors Valentin Gluschko between 1976 and 1985 at the Leningrad gas dynamics laboratory and is now sold by NPO Energomasch . An RD-120 is used in the Zenit rocket as a drive for the second rocket stage and is optimized for operation in a vacuum. The first flight took place in 1985 and 60 units were used by 2006. Although the RD-120 developed significantly less thrust than the RD-171 first stage engine , it was involved in most of the false starts: out of nine false starts, six were second stage failures. Since 2003 a variant of the engine with 10% more thrust has been used on the Zenit 3SL.

technology

The RD-120 is operated with kerosene and liquid oxygen (LOX) and consists of a pre- combustion chamber and a main combustion chamber , a turbine and a gas generator . It is supported by an additional RD-8 engine with four control nozzles that can be swiveled through 33 ° for position control.

Another special feature of the engine is that the power can be reduced to 80% in order to reduce the load on the rocket structure shortly before the burnout. Similar to the RD-253 , the turbine for driving the fuel pumps is located inside the pre-combustion chamber (closed circuit). For this purpose, the entire amount of the oxidizer and a small part of the fuel is supplied, which burns there at a low temperature and drives the turbine. The exhaust gas from the pre-combustion chamber then passes to the main combustion chambers, where the main part of the fuel is supplied and burns. With this design, the engine does not lose any drive gas for the pumps, even with the enormous combustion chamber pressure of over 160 bar.

The RD-120K (also called RD-123) and RD-120M are two variants of the RD-120 engine, which are adapted for operation at sea level and can thus serve as a first-stage engine. They have a nozzle that can be swiveled 6 ° on two levels and is shortened. Development began around 1994 and the prototype of the RD-120K was tested from 1996 onwards, but both variants never reached series production.

Technical specifications

RD-120 RD-120K
Mixing ratio LOX / kerosene 2.6 2.6
Total height 3.87 m 2.80 m
diameter 1.95 m 1.50 m
Dry matter 1125 kg 1433 kg
Thrust / weight ratio (floor / vacuum) - / 75.5 61.7 / 62.1
Combustion chamber diameter ? mm ? mm
Combustion chamber pressure 16.3 MPa 17.2 MPa
Thrust (floor / vacuum) - / 833 kN 867/873 kN
Specific impulse (soil / vacuum) - / 3434 Ns / kg 2923/3296 Ns / kg

Web links

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  1. Bernd Leitenberger: The Zenit carrier rocket. Retrieved July 9, 2008 .
  2. a b RD-120 in the Encyclopedia Astronautica , accessed on April 23, 2012 (English).
  3. RD-120K in the Encyclopedia Astronautica , accessed April 23, 2012 (English).