The Danfoss Motor explains that the ramjet engine has no compressor and cannot be started under static conditions, so it should not be used as a power unit for ordinary aircraft, and often used with other engines to become a combined power unit. Such as ramjet and rocket engine combination, ramjet engine and turbojet engine or turbofan engine combination. An aircraft equipped with a combined power unit that starts a rocket engine, turbojet or turbofan engine at take-off, and when the flight speed is sufficient for the ramjet to operate normally, the ramjet engine is used to close the engine that cooperates with it; during the landing phase When the flight speed of the aircraft is reduced until the ramjet engine is not working properly, the engine that matches it is restarted. If the ramjet engine is used alone as the power unit of the aircraft, then the aircraft must be carried into the air by other aircraft and have a certain speed before the ramjet engine can be started. Ramjet engines or combined ramjet engines are commonly used on missiles and supersonic or subsonic target aircraft.
The ramjet has only three main components - the diffuser, the combustion chamber and the tail nozzle. Although it consists of only three simple pipe-shaped parts, it can emit very large thrusts and the thrust increases rapidly as the flight speed increases. For example, a ramjet with a cross-section of only 1 square meter at 11 km altitude and at a speed of 3.5 times the speed of sound (M = 3.5) can produce a thrust of approximately 30, 000 kg (ie 30 tons). At this time, it propelled power of 414, 000 horsepower, which is equivalent to the power of 200 locomotives. If it is flying at low altitude, it will increase due to the high density of air. How many engines do you have? It will not exceed 1 ton at most. From here you can see its powerful working ability