Combined Cycle Propulsion Systems: A Review of Engine Configurations and Performance Considerations

Combined cycle propulsion systems integrate multiple engine cycles into one package in order to operate efficiently across a wide range of flight speeds and altitudes. However, high-speed aircraft utilizing such propulsion systems have not yet materialized, as successful integration into a platform with comparable size, weight, and complexity as a single cycle engine platform involves addressing multiple problems in many disciplines. Unresolved challenges include material and packaging limitations as well as thermal management and control strategies. This review paper briefly examines the state of the art of combined cycle propulsion systems, including turbine-based combined cycle (TBCC) systems, rocket-based combined cycle (RBCC) systems, and other concepts. We will discuss each engine’s approaches to solving these problems and which problems still remain, and then suggest topics to prioritize for future combined cycle propulsion system research.