JET PROPULSION
 
 

        Near the end of world war 2, allied pilots were startled by a new kind of plane. A German jet fighter Messershmitt me-262. It flew higher, faster and better than other planes at the time. This plane was a jet propelled plane. Today jet fighters fly more swiftly and more gracefully than ever before.

Jet propulsion seeds missiles to there targets. In addition rocket boost earth satellites into orbit. Although most uses of jet propulsion have been for flight, it can also be applied for hydraulic jet propulsion for high speed  and pleasure boats.  In such applications water is taken in at the forward end of the boat, compressed by high pressure pumps, and discharged through a nozzle at the rear of the craft.  The need for efficient pumps and the limitations of boat speeds have not made hydraulic jet propulsion an attractive or economic alternative to propeller driven vessels.
        Jet propulsion is the driving forward of a body by means of a jet or gas fluid. The idea dates back to the 1st century AD when hero of Alexandria built an engine called the aeolipile. He mounted a hollow metal globe with projecting tubes between two pipes so it could spin. Steam entered the globe through the pipes. as it escaped through the bent tubes, the jets of steam spun the globe.    
        Hero's machine illustrates a scientific principle that Sir Isaac Newton formulated in 1687. Newton's third law of motion states that for every action there is an equal and opposite reaction. In hero's machine the jets of stream escaping from the tubes are the action, the spinning of the globe the reaction. The same principal applies to jet engines, and for this reason they are called reaction engines.

     Newton himself designed a jet propelled carriage called Newton's Wagon. A water-filled sphere was heated by fire, creating steam. A large nozzle projected back from the sphere. As the steam escaped from the nozzle, it propelled the wagon forward.

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