RD-809 engine is a restartable main engine of 9000 kgf thrust intended for LV upper stages.

- The engine provides flight control along all reference channels;
- Large service life (more than 4000 s);
- Normal delivery after a check-technological test without following refurbishment;
- Possibiliy to shutdown the engine under expulsion of any propellant;
- Restart capability (ut to 5 times)

Consumer's characteristics of RD-809 engine

The stage flight control is effected by gimballing each combustion chamber (CC) in one plane.
The autonomous main four-chamber engine of five runs, fed by pump is designed under a staged combustion scheme.
The turbine's working medium is oxidizer-reach gas.
The TPU rotor is spinned- up during a startup by pneumatic starter.
The propellants in CC and gas generator (GG) are ignited by dedicated startup fuel.
The engine's control units are piloted by helium delivered into electric-pneumatic valves.
The engine operates in one mode and provides maintenace of specified thrust and propellants mixture ratio.
Pressure indicators installed into the engine issue commands for a shutdown at expulsion of propellants in LV tanks, as well as commands to the control units responsible for a functioning of the TPU rotor spinning-up.

In order to ensure restartability the engine' scheme foresees the following:
1) piloting of control units by high-pressure helium in combination with a principle of oxygen valves self-holding after engine's startup.
2) purging CC injectors duting startup and shutdown, and GG purging at shutdown;
3) system of restartability in GG and CC;
4) the starting tubine is spinned-up from one high-pressure vessel charged with oxidizer before a launch , and with a mixture of GG gas and liquid oxygen before the following starts;
5) system of oxygen system's chilling;

Each engine is delivered to LV integration after performance of a check-technological test without following refurbishment.