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Although jet aircraft were not flown regulary until the 1940s, the idea of an engine producing power by shooting out a stream of gases and compressed air behind it goes back a long way. It is said that the British scientisr Sir Isaac Newton (1642-1727) thought of using the idea in a stream carriage as long ago 1687. Two hundred years later an aeroplane drives by steam jets was designed, although it was never built. Then, at the beginning of the twentieth century, the gas turbine was invented. This works by using hot exhaust gases to drive a turbine, in a similar way to a jet engine. Gas turbines were used in industry, and some people began to wonder if the could be adapted to power aircraft.
The first jet engine
One such person was a British Royal Air Force officer, Frank Whittle (1907- ). Whittle began researching the idea of a gas turbine aircraft engine while he was still a student. By the time he was twenty-three, he had designed a jet engine for use in aircraft, although he lacked the money to build one himself. His RAF employers allowed him time off to work on the project, but showed little interest in the results.
Finally, in 1937, Whittle found some backers to finance the building of his jet engine. This was given its first test runs in the same year. There were teething troubles, but Whittle and his team carried on. Then, in 1938, with war looming, the RAF began to take an interest in Whittle\'s work and gave him the support he needed to speed it up. Two years later, the engine was ready to go into production, and Britain\'s top engineering firm, Rolls-Royce, was chosen to make it.
Jet airlines
When peace came in 1945, the jet technology that had been developed for use in warplanes could be applied to civilian aircraft. One of the problems for airlines before the war had been the inefficiency of piston engines. This meant that they had to carry huge amounts of fuel, and even then had to make frequent stops to take on more. The greater efficiency of jets made the development of jet airliners attractive, especially for intercontinental flights. Not only could jets fly faster, they could also fly higher. This improved their efficiency even more, and also gave a smoother and more comfortable flight for passengers as jets could fly above the clouds, so avoiding any bad weather.
As the new jet airliners carrying larger numbers of passengers came into service, the cost of air travel fell. In the USA, even in the 1930s, it had become commonplace to make long journeys between the major cities by air. Now, all over the world, flying lost its pre-war luxury image and became the normal means of travel for people going abroad on holiday or business trips. A new generation of airliners, the huge jumbo jets, was built to cope with the vast numbers of
people who now wanted to travel by air.
A whole family of jet engines had been developed from the simple original design. One of these was the turbofan. The front cover of the engine conceals a fan which sucks air in and passes it to a compressor before the air and fuel mixture is ignited. The turbofan operates more quietly and uses less fuel than other types of jet engine. Turbofans were used to power the new wide-bodied jumbos.
Faster than sound
Once the jet engine had been developed,. the race was on to build engines that would drive aircraft at ever greater speeds. The lead was taken by the world\'s major air forces. They wanted jet fighters that could fly faster than the enemy\'s, and jet bombers that could fly high and fast, out of reach of enemy defences.
\'Breaking the sound barrier\' became an important target. Sound travels in air at about,1,160 kilometres per hour. At one time, it was thought that at speeds like this the pressure on aircraft frames, and on the bodies of their pilots, would be too much. This was disproved in 1947 when an American Bell X-1 aircraft, powered by a rocket engine, broke the sound barrier without mishap. There was no reason why suitably designed aircraft should not fly at supersonic speeds.
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