The Jet Engine
From the Wright brothers’ first to the airplanes used at the start of World War II, aircraft were powered by engines that worked by repeatedly injecting a small amount of gasoline (or other fuels) inside a cylinder and then igniting it. The resulting bursts of energy turned a propeller, which acted like a powerful fan to push the aircraft along.
The latter years of World War II ushered in the age of the jet engine. A jet engine works quite differently than earlier engines. Imagine standing on a wheeled platform with a bucket of baseballs. When you throw a baseball the platform will roll you in exactly the opposite direction. Throw the baseballs one after another, and you will be pushed down the road. This is explained by Newton’s third law of motion (for every action, there is an equal and opposite reaction). A jet engine does something similar. Fuel is burned and the exhaust gasses are released in one direction, which drives the engine in the opposite direction. Rocket engines also operate this way, although they carry their own supply of oxygen so they can burn fuel in outer space.
These jet aircraft, used principally as fighters, had a tremendous speed advantage over existing planes, but had limited range and less-than-ideal handling. Moreover, they were not produced in sufficient numbers to have a large effect on the course of the war. They did, however, fundamentally redirect the development of both military and commercial aviation after the war.
Jet engines grew larger and more powerful after World War II and became the standard form of aircraft engine for most military and commercial craft. The first jet passenger aircraft used for commercial flights was the De Havilland Comet, a British craft first used in 1949. Other types of jet engines were also introduced. The “turboprop” engine, invented around 1938 and first used in 1950, was used to drive a conventional propeller. A jet engine used this way is ideally suited for helicopters and slower aircraft such as cargo transports.
In addition to aviation, other uses for the jet engine were soon found. For example, in 1946 the General Electric Company adapted its turboprop engine to run an electric generator. By 1948, the company introduced a combination turboprop/generator that was designed to power a locomotive engine. Since that time, this type of electric generator, known as a “gas turbine,” has also been used in many places as the basis of small electric power plants.
Jet engines today are a mature technology, meaning that they are not evolving as rapidly as in the past. However, they are not perfect. They consume vast quantities of fuel (jet fuel is similar to kerosene, derived from petroleum) and contribute significantly to airborne pollution. They are also extremely noisy, causing problems for people who live near airports. They seem to be in little danger of falling out of use, however, because there is no practical substitute for them.