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]
Derivatives
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]
- RD-805 (or RD-802): A proposed upper stage engine of just 19.62 kN (4,410 lbf) of thrust, it would use a single chamber of the RD-8.[10] While many new components would be required, it is considered a low technological risk since it only needs smaller versions of already developed component.[3]
- RD-809 (sometimes identified as RD-809M): It is an RD-8 re arranged to minimize its diameter. It would use practically every single component of the RD-8, but arranged without the big hollow section in the middle. It was a proposed engine for a proposed liquid upper stage of the Antares rocket, then named Taurus II.[3] It would be capable of five engine burns in a single mission.[11]
- RD-809K: A proposed single nozzle version of the RD-8. It would mix most principal elements of the RD-8 like the turbopumps with a main combustion chamber and nozzle adapted from the RD-861K.[3][12] It would be capable of 4 starts in a single mission.[12] It is expected to be used in a dual engine configuration in the Mayak upper stage.[3]
See also
- RD-120 – The Zenit second stage main engine which is the companion of the RD-8 and the basis for some of its derivatives.
- Zenit – The launch vehicle family for which the RD-8 was developed.
- Mayak – Prospective Ukrainian launch vehicle family for which the RD-805, RD-809 and RD-809K are being developed.
- Yuzhnoe Design Bureau - The RD-8 designer bureau.
- Yuzhmash - A multi-product machine-building company that's closely related to Yuzhnoe and manufactures the RD-8.