# UAV Detection Using Thrust Engine Electromagnetic Spectra
### Types of Engines for UAV's Propulsion  
For any UAV to fly, propulsion is a must. An overview of the primary thrust engine types for UAV flight performance is given with an emphasis on internal combustion and electric engines. An internal combustion engine, called a piston, often known as a reciprocating engine, employs one or more reciprocating pistons to transform pressure into rotational motion to generate thrust power from liquid fuel. An electrical device that transforms electrical energy into mechanical energy is known as an electric motor. The interplay of a motor's magnetic field and electric current in its wire windings produces the rotation force of the motor shaft. An internal combustion engine, known as a two-stroke, completes two cycles in one shaft revolution. In a two-stroke engine, the intake and exhaust processes occur simultaneously at the end of the combustion stroke and at the beginning of the compression stroke. Compared to other forms of internal combustion engines, this type of engine has a high power-to-weight ratio because of the tremendous power that can be achieved in this way. These engines are fairly lightweight and are frequently utilized for UAV propulsion due to their straightforward construction. A four-stroke engine has a four-stroke duty cycle. They are the intake stroke, compression stroke, power stroke, and exhaust stroke. Four-stroke engines tend to be heavier because they use oil pumps and oil reservoirs to lubricate the engine. The engine has a valve system, which also adds weight. A four-stroke engine provides one power stroke for every two piston cycles (or four piston strokes), resulting in a lower power-to-weight ratio. However, this type of engine is much more reliable and energy efficient than a two-stroke engine due to the built-in oil lubrication system. A four-stroke engine is typically used for the propulsion of long-life military-type UAVs. The Wankel engine has been redesigned for use in UAV propulsion as a hybrid power generation unit. Jet engines are used in large UAVs. A jet-type engine's propulsion is produced by releasing liquid fuel combustion products at high velocities, thus inducing thrust that acts as the thrust of the UAV. Rocket engines are powered by liquid or solid fuels. The driving force is obtained by burning fuel. This type of motor has limited use in UAV propulsion because it does not have a mechanism to control the thrust. There is no way to stop the  
Figure 1: The main UAV propulsion energy and engine types. engine before all fuel is burned. A supercharged jet engine has different stages of rotating blades. Air in the engine enters each stage and each stage compresses the air into stages. The flow path through which air passes gradually decreases in area as it progresses to the next stage. At the end of the compressor, there is a diffuser that slows down the airflow to further increase the static pressure. An aircraft propeller or a turbofan enclosed in an enclosure is driven by a turbopro or turbofan engine. The compressor is powered in part by the energy produced by the turbine, and the remaining energy is transferred through the reduction gears to the propeller or turbofan. The fundamental distinction between a turbofan and a turbojet engine is that a turbofan uses almost all of its power to drive a propeller, whereas a turbojet uses its exhaust gases to produce tremendous thrust. The take-off, flight, positioning, and landing of a UAV are often performed with electric propulsion motors. The often-referred-to \"copter\" UAV can conduct take-off, flight, positioning, and landing procedures with a minimum of three thrust engines. The copter can be placed when the thrust of the electric motors is adjusted and the position and flight path of the UAV are maintained. A tiny copter UAV can employ a brushed direct current (DC) electric motor as its thrust motor. Due to the existence of airfoil-style wings, it may also power a fixed-wing UAV, eliminating the requirement to generate lifting force.