RD-8
| Country of origin | Soviet Union |
|---|---|
| First flight | April 13, 1985 |
| Designer | Yuzhnoye Design Bureau |
| Manufacturer | Yuzhmash |
| Application | Second Stage Vernier |
| Associated L/V | 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 (vac.) | 78.45 kN (17,640 lbf) |
| Chamber pressure | 7.747 MPa (1,123.6 psi) |
| Isp (vac.) | 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 weight | 380 kg (840 lb) |
| Used in | |
| Zenit family second stage | |
| References | |
| References | |
The RD-8 (Russian: РД-8 and GRAU Index: 11D513) is an Ukrainian liquid propellant rocket engine burning LOX and RG-1 (a rocket grade kerosene) in a oxidizer rich staged combustion cycle. It has a four combustion chambers that provide thrust vector control by gimbaling each of the nozzles in a single axis by +/- 33°. It was designed in Dnipropetrovsk by the Yuzhnoye Design Bureau as the vernier thruster of the Zenit (GRAU: 11K77) second stage. As such, it has always been paired with the RD-120 engine as main propulsion.
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). 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.
The engine itself is built like a hollow cylinder, with a cylindrical space in the center so the RD-120 nozzle can pass through.
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. 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.
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