From four-stroke engines to gas turbine engines, from the Otto company to Rolls Royce, engines and propulsion systems have changed the world we live in for almost one hundred and fifty years. With each passing year, something new happens; something more complex but more advanced in terms of propulsion systems. Even though these systems seem to change every year and appear more complex, the principle behind the structure has remained virtually the same since the first internal combustion engine, created by Nicolas August Otto in the late 1800s. The principle has remained the same, so much so that the four-stroke system we know today is often called the "Otto cycle." Over time there have been slight variations in the manufacture of the four-stroke system, but they all operate on similar principles to the Otto cycle. The four-stroke engine has become so diverse that it can be seen in a number of different vehicle types such as cars, trucks, trains, ships and of course airplanes; each with their own slight differences to help them function in their required environment. This can be seen with aircraft that use jet turbines instead of piston engines for the simple fact that this is the environment in which they operate. This can refer to the heights at which certain aircraft fly as well as the speeds at which they can cruise to identify what would be the most appropriate propulsion mechanism to use for the given scenario. Nicolas Otto, born in 1832, was a German inventor who is best known as the inventor of the first internal combustion engine in which he efficiently burned fuel directly in a piston chamber. , after being inspired by Étienne Lenoir who created the first two-stroke engine. Although Otto may have... middle of paper ......different types of engine designs were developed from the original. However, each model may be slightly different in terms of appearance, operation or size, but in reality the principle behind each variation is always exactly the same. This is also quite easy to identify with turbine engines because the gas turbine engine is the basis of all turbines with variations and modifications made depending on the gas turbine. The turbine may be slightly more expensive to operate than the piston engine, but the reliability of the turbine engine is significantly higher, showing that it may be the propulsion choice in terms of safety. Again, this depends on where the aircraft will be used and how this may not always be the case. Pistons or turbines, Rolls Royce or the Otto company all strive to achieve the same thing in a different way, provide a source of propulsion.