Survey on the mode transition technique in combined cycle propulsion systems

With the maturation of the scramjet technologies, the urgent development of the combined cycle propulsion system has been put forward, and it can help the vehicle to launch and land horizontally. In the current survey, the research status on the mode transition of the combined cycle engines has been reviewed in detail, and three typical mode transition processes have been summarized, namely the ejector/ramjet mode transition for the rocket-based combined cycle engine, the turbojet/ramjet mode transition for the turbine-based combined cycle engine and the ramjet/scramjet mode transition for the combined cycle engines. Lastly, some suggestions on the development of the combined cycle propulsion systems have been put forward.