RD-809

Yuzhnoye LOx/Kerosene rocket engine. Upper stages. 2007 design concept for a four-chamber restartable main engine for launch vehicle upper stages.

The engine was evidently a restartable version of the RD-8 Zenit-2 second stage vernier engine assembly and had the following features:

• Long service life (4000 seconds, five restarts)
• Designed for installation in the upper stage after a factory firing test without the need for post -test refurbishment
• Stage flight control is effected by gimballing each combustion chamber ±10% in one plane.
• All four-chambers pump-fed using a combustion scheme with oxidizer-rich gas feeding the turbopumps.
• Turbine rotor spun-up by a pneumatic starter
• Propellants in the combustion chamber and gas generator ignited by dedicated startup fuel
• Pneumatic gimbal units used helium gas delivered via electric-pneumatic valves
• Single-mode engine providing constant thrust and propellant mixture ratio within ±4.5% / ±8.
• Pressure sensors provide data for automatic startup and shutdown of engine

Chambers: 4. Chamber Pressure: 87.75 bar. Oxidizer to Fuel Ratio: 2.5. Restarts: 6.