NPO Energomash

RD-120 engines for second stage of the “Zenit” launch-vehicle
 
The development of RD-120 engines for a second stage of “Zenit” launch-vehicle was begun in 1976. This single chamber engine is created under the scheme with afterburning of oxidizer-rich gas and has high value of specific impulse of thrust - 350 sec in vacuum – due to large expansion ratio. The rocket flight control is conducting thanks to use the independent four-chamber steering engine of “Yuzhnoye” Design Bureau development. The engine has a high level of reliability - not below 0,992, each engine passes resource acceptance-technological fire test with the subsequent delivery to the customer without a reassembling, thus a safe life of the engine - not less five operating safe lifes over nominal one. The maiden flight of “Zenit” launch-vehicle with the RD-120 engine was conducte in April, 1985. 177 engines are made, 560 fire tests with common running time of 139186 sec are conducted.

The experimental development of RD-120 engines was conducted at NPO Energomash, including their production till 1982, and the serial production of RD-120 engines is conducting at “Yuzhmash” plant in Dnepropetrovsk, Ukraine. 
Main parameters of the RD-120 engine family
 
Liquid propellant rocket engine with afterburning of oxidizer-rich gas
Propellant                                                          liquid oxygen + kerosene
 
Engine modifications
RD-120
RD-120 forced

RD-120K

Thrust, sea level/ vacuum, tf
- / 85
- / 93
80 / 87
Specific impulse, sea level/ vacuum, sec
- / 350
- / 350
304,4 / 330
Combustion chamber pressure, kgf/cm2
166
181,6
179,8
Weight, dry / filled, kg
1125 / 1285
1125 / 1285
1080
Overall dimensions, height / diameter, mm
3872 / 1954
3872 / 1954
2435 / 1400
Period of development
1976 - 1985
2001 - 2003
1986 -
Purpose
“Zenit” LV
“Zenit 3SL” LV
perspective LV
 
The considerable margins of functionability of main units and engine as a whole have allowed to create on its basis the forced (on 10 % thrust) modification providing a level of thrust 93 tf and with a guarantee reserve in 5 %. The running safe life of one engine was achieved up to 4260 sec, and on number of starts - up to 19, that allows to foresee the RD-120 engine as the basis for development of the reusable engine. These activities on modernization of the engine were made in 2001-2003. 4 engines have passed 28 fire tests with running time of 8135 sec. The maiden launch of “Zenit” launch-vehicle with the forced engine RD-120 under the “Sea Launch” program is successfully conducted in June 2003.
In 2005 the interbranch tests of the modified engine are successfully completed, that allows to use it in interests of Federal Space Agency and Ministry of Defence of Russian Federation.
Forced RD-120 engines have operating in “Land Launch”, “Sea Launch” and Federal Space program of Russia.
Sea-level RD-120 engine modification (with the short nozzle) also is designed, which is intended for first stages of the perspective launch-vehicles. 2 fire tests of one engine were conducted. The single chamber engine with the short nozzle has 2 (or 4) steering chambers for rocket flight control.