RD-0120

The RD-0120 (Russian: Ракетный Двигатель-0120, romanized: Raketnyy Dvigatel-0120, lit. 'Rocket Engine 0120', GRAU index: 11D122) was the Energia core rocket engine, fueled by LH2/LOX, roughly equivalent to the RS-25 (Space Shuttle Main Engine, SSME). These were attached to the Energia core rather than the orbiter, so were not recoverable after a flight, but created a more modular design (the Energia core could be used for a variety of missions besides launching the shuttle). The RD-0120 and the RS-25 have both similarities and differences. The RD-0120 achieved a slightly higher specific impulse and combustion chamber pressure with reduced complexity and cost (but it was single-use), as compared to the RS-25. It uses a fuel-rich staged combustion cycle and a single shaft to drive both the fuel and oxidizer turbopumps. Some of the Russian design features, such as the simpler and cheaper channel wall nozzles, were evaluated by Rocketdyne for possible upgrades to the RS-25. It achieved combustion stability without the acoustic resonance chambers that the RS-25 required.