what is the differences between RAMJET, PULSEJET and SCRAMJET?

A Ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed, thus cannot move an aircraft from a standstill. Ramjets therefore require some other propulsion system to accelerate the vehicle to a speed where the ramjet begins to produce thrust. Ramjets work most efficiently at speeds around Mach 3. This type of engine can operate up to speeds of Mach 6.

Ramjets can be particularly useful in applications requiring a small and simple mechanism for high-speed use, such as missiles. Weapon designers are looking to use ramjet technology in artillery shells to give added range; a 120-mm mortar shell, if assisted by a ramjet, is thought to be able to attain a range of 22 mi (35 km).[1] They have also been used successfully, though not efficiently, as tip jets on the end of helicopter rotors.[2]

Ramjets are frequently confused with pulsejets, which use an intermittent combustion, but ramjets employ a continuous combustion process. They are also confused with scramjets, a similar, but less efficient system.

Both are types of experimental engine designed for speeds greater than that of sound, in the hypersonic realm. They are jet engines with no moving parts, relying on the enormous pressures created by supersonic airflow into the engine to ignite fuel without needing the compressors and turbines used in the turbofan engines found on conventional jet planes. In a ramjet, the combustion chamber - where the air is mixed with fuel and ignited - only works at subsonic speeds. So the intake slows the air down, releasing some of its energy as a shock wave, but this reduces fuel efficiency. The scramjet is an innovation on the ramjet in which the combustion chamber is specially designed to operate with supersonic airflow. Scramjet is simply an acronym for 'supersonic combustion' ramjet.

Ramjet Vs Scramjet

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what is the differences between RAMJET, PULSEJET and SCRAMJET?

just curious...:P