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History
The basic principle behind the jet engine was first envisioned in the 1700s by the British inventor Sir Isaac Newton. Based on his third law of motion, Newton theorized that a body could be rapidly propelled forward by the rear-facing discharge of a controlled explosion. Although the concept was left largely untapped for two centuries, it was successfully exploited in 1937 by Hans Von Ohain for use in the German military. By the 1950s, turbojet technology had found its way to the civilian market in the De Havilland Comet, the first commercial jetliner. Although the Comet was besieged by design flaws and aerodynamic design has evolved considerably since turbojets first powered flight, the jet engine has remained largely unchanged since that time.
Function
The massive amount of thrust produced starts with a large fan in the front of the engine enclosure. This fan serves to ingest air into the engine, where it is compressed (in the aptly named compressor) by a series of numerous fans with many small blades. The compressed air is forced into a combustion chamber where it is mixed with fuel and ignited by an electric spark. The hyper-compressed air expands at a very rapid pace as part of the combustion, and the rapidly expanding gasses are directed out the rear of the engine. The velocity with which the gas escapes the jet engine creates a tremendous forward thrust that is great enough to propel a fully loaded jetliner through the air at close to the speed of sound.
Misconceptions
As propulsion goes, jet planes are in a league of their own. Unlike cars, jet planes do not use their wheels for forward movement; the wheels roll independent of any thrust and are often completely disconnected from the rest of the plane's propulsion system. In addition, jet planes differ from their propeller-based counterparts; often smaller in size, propeller-powered planes rely on two, three or four-bladed propellers to pull the plane forward through the air. While the intake of a jet engine may look somewhat similar to a propeller, the large fan serves only to ingest air and not as a primary source of thrust.
Benefits
Starting in the 1930s for military aircraft and in the 1950s for commercial passengers, jet planes completely revolutionized air travel. With twin jet engines, an airplane could reach speeds in excess of 600 mph, significantly shortening travel time for air passengers and dramatically improving response time for military maneuvers. As jet fighters found a home in the military, advanced tactical fighting became possible where aircraft had previously been used generally in supporting roles. Finally, jet engines are inherently quieter than propeller planes, adding a significant level of acoustic comfort to flight.
Effects
Because of the significant reduction in travel time, commercial air travel saw a considerable rise after the advent of the jet engine. Because jet planes were faster, quieter, usually larger and perceived as safer, air travel picked up considerably in the 1950s and 1960s; the increase was so significant, in fact, that the term "jet age" was coined to describe the two decades. Because jet airplanes are much faster and can carry larger loads than propeller planes, the shipping and freight industries also reaped benefits from the use of jet planes; although deliveries were often shipped by train or other ground-based methods prior to the 1950s, jet planes allowed overnight (and, for a hefty fee, even "same day") deliveries between cities separated by hundreds or even thousands of miles. Finally, jet engines are somewhat more fuel efficient than their propeller-based peers, so the environment also benefited from the advent of the jet plane.