LIQUID-PROPELLANT ROCKET ENGINES
PROPULSION SYSTEM FOR MANNED LUNAR VEHICLE
Propulsion engineers of Yuzhnoye design office carried out an important and complex task: they developed an 11D40 propulsion system for the lunar landing vehicle.The 11D410 propulsion system consisted of an RD-858 main engine and an RD-859 backup engine. The propulsion system would provide a soft landing on the surface of the Moon, liftoff from the Moon, and injection of the lunar vehicle into an elliptical orbit of the Moon’s artificial satellite.
The lunar vehicle would fly with a crew onboard; therefore, the most stringent requirements were placed upon the engine reliability. The reliability had to be proven by a great number of tests that simulated full-scale conditions. To provide a soft landing on the Moon and liftoff, the RD-858 engine features a dual-burn capability and two thrust levels: a main mode and a deep-throttling mode. A throttling range is ±9.8% in the main mode and ±35% in the deep-throttling mode. Such deep throttling required specific structural modifications to provide the engine chamber stability with reliable cooling.
The two-chamber RD-859 backup engine features one thrust level with the throttling range of ±9.8%.
The most stringent requirements were applied to the engine turbopump assemblies, and specifically to the face seals separating the oxidizer pump from the turbine. A significant number of tests were required to select the most reliable and efficient friction pair. The structure proved to be robust: the turbopump assemblies had a life estimated at thousands of seconds.
To provide reliable cooling, the chamber’s high-temperature flux area features machined helical flutes with optimal variable cross-section on complex-geometry parts.
The number of ignitions per engine reached twelve instead of two required in flight. The backup engine features a unique capability of ignition after a three-second period between cutoff and reignition. Processes of the engine cutoff, chamber pipeline emptying, and reignition after the three-second pause were thoroughly studied to prove the behavior convergence. The reignition parameters during tests were the same as those of the first ignition. None of the existing engines with a turbopump feed system was able to provide such performance. For liquid-propellant engines with turbopump feed systems providing a wide range of throttling, these engines featured quite a high specific impulse for such thrust level. The propulsion system mass and dimensions go to prove high design efficiency, even taking into account the integrated engine performance control and throttling systems. A total mass of the engines is 110 kg for a total thrust of 4100 kgf. For comparison, the mass of the Ariane-5 upper-stage engine exceeds 100 kg at 2700 kgf.
The test campaign was extensive: 181 RD-858 engines with a total running time of 253281 seconds and 181 RD-859 engines with a total running time of 209463 seconds. Eleven 11D410 propulsion systems were tested, with emergency simulated.
On the whole, the liquid-propellant propulsion system of the lunar landing vehicle is among the most reliable in its class. Three propulsion systems were successfully tested in Earth orbit onboard the T-2K spacecraft launched by the R-7 launch vehicle.
MAIN ENGINES
Name | Vacuum thrust, kgf | Propellants | Vacuum specific impulse, kgf?s/kg | Mass, kg | Missile/Launch Vehicle |
---|---|---|---|---|---|
RD853 | 47680 | Oxidizer: nitric acid + 27% N2O4 Fuel: UDMH | 300,7 | 485 | 8K66 (SS-7) missile second stage |
RD854 | 7700 | Oxidizer: NTO Fuel: UDMH | 312,2 | 100 | 8K69 (SS-9-2) boost stage: deceleration and control of the orbital spacecraft in all stabilization axes |
RD857 | 14000 | Oxidizer: NTO Fuel: UDMH | 329,5 | 190 | 8K99 (SS-15) missile second stage |
RD861 | 8026 | Oxidizer: NTO Fuel: UDMH | 317 | 123 | 11K68 (Cyclone-3) launch vehicle third stage: thrusting and control in powered flight in all stabilization axes |
RD862 | 14544 | Oxidizer: NTO Fuel: UDMH | 331 | 192 | 15А15 and 15А16 (SS-17-1 and SS-17-2) missile second stages |
RD864 | 2060 | Oxidizer: NTO Fuel: UDMH | 309 | 199 | 15А18 (SS-18-2) missile: two thrust modes and control in all stabilization axes during the post-boost vehicle flight |
RD866 | 513,5 | Oxidizer: NTO Fuel: UDMH | 323,1 | 125,4 | Space tug engine; installed in 15Zh44, 15Zh52, 15Zh61, 15Zh60 missile nose cones |
RD868 | 2371 | Oxidizer: NTO Fuel: UDMH | 325 | 125 | Zenit and Cyclone-4 apogee stages |
RD869 | 2087 | Oxidizer: nitric acid + Fuel: UDMH | 313 | 196 | Space tug engine; 15А18М (SS-18-3) missile third stage flight control in all stabilization axes |