The RD-861K engine is intended for thrust creation and flight control of Cyclone-4 LV third stage. The engine is designed on the basis of the high-reliable serial RD-861 engine used on the Cyclone LV third stage.

Usage of basic components of the previous engine (RD-861) ensures high energetic performance and reliability.

The one-chamber pump-fed with self-igniting propellants rocket is designed under the scheme without afterburning of generator gas.

The RD-861K engine has the following characteristics in comparison with its forerunner:

  • the engine’s specific impulse is increased in 15.6 s;
  • number of restarts in flight is increased;
  • the burning time is increased by 3 times.

The RD-861K has next advantages:

  • the thrust vector control system is fed by high-pressure fuel;
  • the propellants mixture ratio is ensured with accuracy of ±1,0%, on conditions that ordinary operating terms are provided.


Technical characteristics Value
Vacuum thrust, kgf 7916
Vacuum specific propulsive burn, s 330
Mass, kg 207
Propellant mixture 2.412
Number of restarts 5
Burn time, с 481