RL10CX-3EL: Next Generation Extended Life Engines for the Commercial Passenger Transport

Abstract

The RL10 is the highest performance upper stage rocket engine in the world. It has provided precisely controlled, reliable power for a wide variety of earth orbital and interplanetary missions. Originally designed as a 15K lb thrust engine for the Atlas Centaur high energy upper stage, the engine has been upgraded numerous times to meet the continuously evolving needs of the launch community. RL10 engine models currently in production generate nearly 25K lbs of thrust with a specific impulse of 465 seconds. RL10 engines power the upper stages of the United Launch Alliance (ULA) Atlas and Delta launch vehicles and the NASA Space Launch System (SLS) Interim Cryogenic Propulsion Stage (ICPS). RL10 engine models are currently being developed for the ULA Vulcan Centaur V and the NASA SLS Exploration Upper Stage (EUS). The RL10 engine family has accumulated over 2.4 million seconds of hot fire time and 15,000 firings. It has a demonstrated reliability of 0.9998. The next generation, extended life RL10CX-3EL engine has been selected for the re-usable, space based, Commercial Passenger Transport (CPT) vehicle not only because of its outstanding performance and high reliability, but also because its operating cycle makes it particularly well suited to meet the extreme service life demands of the CPT mission. The RL10 engine incorporates a simple, low power density, closed expander operating cycle. The energy needed to drive the turbomachinery comes from the heat absorbed by the hydrogen propellant that is used to cool the combustion chamber walls. This warm hydrogen is then expanded across the turbine to drive the fuel and oxidizer pumps. This cycle reduces the operating stresses on the engine components and enables longer service life applications and unlimited restart capability. This paper focuses on the attributes of the RL10CX-3EL engine.