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Jet propulsion is produced by some reaction engines or animals when thrust is generated by a fast moving jet of fluid in accordance with Newton's laws of motion.It is most effective when the Reynolds number is high—that is, the object being propelled is relatively large and passing through a low-viscosity medium.
A jet engine is a type of reaction engine, discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include rocket , water jet , and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as a turbojet , turbofan ...
This is the first truly usable jet engine. The engine flies on a Heinkel He 118 later that year, eventually becoming the first aircraft to be powered by jet power alone. This engine is tested until it burns out after a few months, and a second is readied for flight. 1938: Wagner's axial-flow engine is tested at Junkers.
The Heinkel-Hirth aviation powerplant firm also tried to create a more powerful turbojet engine, the Heinkel HeS 011 of nearly 3,000 pounds of thrust at full power, very late in the war to improve the propulsion options available to new German military jet aircraft designs, and to improve the performance of existing designs. It used a unique ...
The jet velocity exceeds the speed of a subsonic aircraft by too great an amount to be an economical method of subsonic aircraft propulsion. The purpose behind the jet engine is to convert fuel energy into kinetic energy of the cycle air but after the thrust-producing momentum has appeared the unwanted byproduct is the wake velocity which ...
An airbreathing jet engine (or ducted jet engine) is a jet engine in which the exhaust gas which supplies jet propulsion is atmospheric air, [1] which is taken in, compressed, heated, and expanded back to atmospheric pressure through a propelling nozzle. [2]
Similarly to jet engines, matching the exhaust speed and the vehicle speed gives optimum efficiency, in theory. However, in practice, this results in a very low specific impulse, causing much greater losses due to the need for exponentially larger masses of propellant. Unlike ducted engines, rockets give thrust even when the two speeds are equal.
A pump-jet, hydrojet, water jet, or jet drive uses a ducted propeller (axial-flow pump), centrifugal pump, or mixed flow pump to create a jet of water for propulsion. These incorporate an intake for source water and a nozzle to direct its flow out, generating momentum, and in most cases, employing thrust vectoring to steer the craft.