Pulse Jet Engine (Pulse Jet Engine) is a type of jet engine that has received attention due to the simplicity of its design and the ability to produce propulsion power in certain conditions, especially in small aircraft and military and commercial applications. This engine is included in the category of jet engines and unlike turbine engines, it is less complicated. History of the pulse jet engine The concept of the pulse jet engine dates back to the early 20th century, but its development peaked mainly during World War II. The most famous use of this engine was in Nazi Germany's V-1 flying bomb, which is known as the first cruise missile. This technology was very effective at that time due to the simplicity of construction and the low cost of production. Principles of operation of the pulse jet engine The pulse jet engine works based on a simple cycle: 1. Fuel and air intake: the mixture of fuel and air enters the combustion chamber. 2. Combustion: The mixture of fuel and air ignites in the combustion chamber and produces hot gases. 3. Ejection of gases: Hot gases are thrown out at high speed through the exit nozzle and create propulsive force. 4. Repeating the cycle: Due to the negative pressure created in the combustion chamber, fresh air enters and the cycle repeats again. Design features 1. Simple structure: The pulse jet engine has few or no moving parts in some versions. 2. Light weight: Due to the simple design and no heavy parts, these motors are very light in weight. 3. Low manufacturing cost: The manufacturing of this engine does not require advanced technology or special materials. 4. High noise: One of the disadvantages of the pulse jet engine is the production of high noise, which can cause problems in civilian applications. Types of pulse jet engine 1. Valved Pulse Jet: In this type of engine, there are valves to control the flow of air and fuel. 2. Valveless Pulse Jet: This type of engine does not use mechanical valves and requires a simpler design. Applications of pulse jet engine 1. Missiles and drones: due to their simplicity and low cost, pulse jet engines are used in military systems such as missiles and drones. 2. Experimental and Research: These engines are used in research projects and engineering experiments. 3. Special commercial applications: sometimes used in the production of small aircraft or special tools that require simple propulsion. Advantages and Disadvantages Advantages: • Simple and inexpensive design: Unlike turbine jet engines, pulse jets do not require complex components. • Light weight: suitable for light weight devices. • Operation at low speeds: Unlike turbojets, these engines perform well at low speeds. Disadvantages: • Low efficiency: compared to other engines, it has lower thermal efficiency and fuel consumption. • High noise: causes restrictions on commercial and civilian use. • Limited lifetime: due to thermal and mechanical stresses, the useful life of these engines is less than other types. Modern Developments In recent decades, efforts have been made to optimize pulse jet engines. Techniques such as the use of advanced materials, optimization of aerodynamic design, and precise control of the combustion process have made these engines find new applications. One area of ​​research is combining pulse jet engines with other systems such as ramjets to increase efficiency and effective range. Conclusion Pulse jet engine has a special place in the history of aerospace and military engineering due to its simple design and ability to produce propulsion power in special conditions. Although these engines are used less in modern aircraft due to technical limitations, they still maintain their place in research and military projects as an attractive and low-cost technology.