NK-33

The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau. They were intended for the ill-fated Soviet N-1 rocket moon shot. The NK-33 engine is among the highest thrust-to-weight ratio of any Earth-launchable rocket engine, while achieving a very high specific impulse. NK-33 was by many measures the highest performance LOX/Kerosene rocket engine ever created.

The NK-43 is similar to the NK-33, but is designed for an upper stage, not a first stage. It has a longer nozzle, optimized for operation at altitude, where ambient air pressure is low or perhaps zero. This gives it a higher thrust and specific impulse, but makes it longer and heavier.

In 2010 stockpiled NK-33 engines were successfully tested for use by the Orbital Sciences Antares light-to-medium-lift launcher.