Development, upgrade phases and results of fifty years of operation of our country’s first closed-loop liquid rocket engine

The paper presents the results of work conducted at OKB-1 (RSC Energia) to develop our country’s first closed-loop (with two-stage combustion) liquid rocket engine (LRE) for upper stage L of the Molniya rocket system. Its development marked the transition of rocket technology to closed-loop LRE, which enabled an almost complete utilization of energy contained in various types of rocket propellants, a higher pressure in combustion chambers and significantly improved LRE performance. All this was impossible to achieve in open-loop engines due to higher losses in turbopump drives. The experience gained during development of this engine enables RSC Energia to develop main and steering engines for upper stages of Block D and DM type and Buran Orbiter which had high performance and reliability. The results of this work are still used by RSC Energia for the development of an advanced multifunctional LRE, the chamber of which is cooled with liquid oxygen.