The RD-8 (Russian: РД-8 and GRAU Index: 11D513) is a Soviet / Ukrainian liquid propellant rocket engine burning LOX and RG-1 (a rocket grade kerosene) in an oxidizer rich staged combustion cycle.[5][6] It has a four combustion chambers that provide thrust vector control by gimbaling each of the nozzles in a single axis ±33°.[2] It was designed in Dnipropetrovsk by the Yuzhnoye Design Bureau as the vernier thruster of the Zenit (GRAU: 11K77) second stage.[7] As such, it has always been paired with the RD-120 engine for main propulsion.[8][1]
Country of origin | Soviet Union |
---|---|
First flight | April 13, 1985 |
Designer | Yuzhnoye Design Bureau |
Manufacturer | Yuzhmash |
Application | Second Stage Vernier |
Associated LV | Zenit |
Successor | RD-809M |
Status | In Production |
Liquid-fuel engine | |
Propellant | LOX / RG-1 |
Mixture ratio | 2.4 |
Cycle | Staged Combustion |
Configuration | |
Chamber | 4 |
Performance | |
Thrust, vacuum | 78.45 kN (17,640 lbf) |
Chamber pressure | 7.747 MPa (1,123.6 psi) |
Specific impulse, vacuum | 342 s (3.35 km/s) |
Burn time | 1100 s |
Gimbal range | ±33° |
Dimensions | |
Length | 1,500 mm (59 in) |
Diameter | 4,000 mm (160 in) |
Dry mass | 380 kg (840 lb) |
Used in | |
Zenit family second stage | |
References | |
References | [1][2][3][4][5][6] |
It can only be started once, and as a high altitude engine it has a thrust of 78.45 kN (17,640 lbf) and a specific impulse of 342 s (3.35 km/s).[5][6] It is the first ever steering engine to use the staged combustion cycle, and as such is the basis for a family of planned engines for the Mayak launch vehicle family.[3]
The engine itself is built like a hollow cylinder, with a cylindrical space in the center so the RD-120 nozzle can pass through.[9]
Whilst Yuzhnoye's propulsion experience had been mostly on hypergolic propellants engines, like RD-855 or RD-861, they are considered too toxic for current ecological standards.[7][8] While Yuzhnoye still offer to develop hypergolic propulsion, such as RD-843 for the Vega's AVUM stage or the Tsyklon-4 project, Yuzhnoye selected a more environmentally friendly LOX and kerosene propellant for the Mayak launch vehicle family.[3]
Not only had Yuzhnoye mastered the most complex cycle for the propellant (oxidizer rich staged combustion cycle) with the RD-8, but they had worked closely with NPO Energomash during the RD-120 program. The manufacturing is done at its sister company of Yuzhmash in Dnipropetrovsk, and the RD-120 thrust augmentation project of 2001 to 2003 had been a mixed project between the three companies.[3]
On the base of this experience, a family of derivatives engines were proposed. While the RD-801 and RD-810 are really just based on the general technology, the other members of the family are related enough that they reuse many components of the RD-8.[3] One characteristic of this family is the limitation of keeping the preburner output temperature below 500 °C (932 °F).[3]