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 nearly one hundred and fifty years. With each passing year something new arrives; something more complex and at the same time more advanced in terms of propulsion systems. Although these systems may seem to change every year and may seem more complex, the principle behind the structure has remained virtually the same since the first internal combustion engine, created by Nicolaus 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 referred to as the "Otto cycle". Over time, there have been slight variations in the production of the four-stroke system, but they all work according to similar principles as the Otto cycle. The four-stroke engine has become so diverse that it can be seen in numerous different vehicle types such as automobiles, trucks, trains, marine vessels and of course airplanes; each with their own slight differences to help them perform in the required environment. This can be seen with aircraft that use jet turbines instead of piston engines for the simple fact that it is the environment in which they operate. This can refer to the heights at which certain aircraft fly and the speeds at which they can cruise to identify what would be the most appropriate propulsion mechanism to use for the given scenario. Nicolaus Otto, born 1832, was a German inventor best known as the inventor of the first internal combustion engine in which he efficiently burned fuel directly in a piston chamber, having been inspired by Étienne Lenoir who created the first two times. Although Otto may have... middle of paper... engines have had different types of engine models developed based on the original, however, each model may be slightly different in appearance, operation or size but in reality , the principle behind each variation is always exactly the same. This is quite easy to identify with turbine engines also because the gas turbine engine is the basis of all turbines with variations and modifications made based on the gas turbine. The turbine may be slightly more expensive to operate than the piston engine, however the reliability of the turbine engine is significantly higher, showing that it could be the propulsion choice in terms of safety. Again, though, depending on where the aircraft will be used and how, this may not always be the case. Pistons or turbines, Rolls Royce or Otto Company all strive to achieve the same thing differently, they provide a source of propulsion.