The period between 1945 and 1979 is sometimes called the post-war era or the period of the post-war political consensus. During this period, aviation was dominated by the arrival of the Jet Age. In civil aviation, the jet engine allowed a huge expansion of commercial air travel, while in military aviation it led to the widespread introduction of supersonic aircraft. By the end of the Second World War Germany and Britain already had operational jet aircraft in military service. The next few years saw jet engines being developed by all the major powers and military jet aircraft entering service with their air forces. The Soviets' most important design bureau for future jet fighter development in the decades to come, Mikoyan-Gurevich, started preparing for building swept-winged jet aircraft with the small, experimental piston-engined MiG-8 Utka pusher, which flew with slightly swept-back wings only months after V-E Day. Supersonic flight was achieved in 1947 by the American Bell X-1 rocket plane, however the use of rocket engines would prove short lived. The development of the afterburner soon allowed jet engines to provide similar levels of thrust and longer range, while needing no oxidant and being safer to handle. The first supersonic jet to enter service was the North American F-100 Super Sabre, in 1954. Meanwhile, commercial jetliners were being developed with the first of these, the British de Havilland Comet, first flying in 1949 and entering service in 1952. The Comet suffered from a new and unexpected problem now known as metal fatigue, several examples crashed and by the time a new version was introduced, American types such as the Boeing 707 had overtaken its design and it was not a commercial success. These types and their descendants contributed to an era of great social change, typified by popular phrases such as "the jet set" and introducing new medical syndromes such as jet lag. The propulsive efficiency of jet engines is inversely related to the exhaust velocity. The turbofan engine improves on the propulsive efficiency of the turbojet by accelerating a larger amount of air to a lower velocity. The overall gain in efficiency increases the range and lowers the cost of operation for a given aircraft. Development had begun in both Britain and Germany during the war but the first production version, the Rolls-Royce Conway did not come into use until around 1960. Attempts were made to develop a supersonic airliner, with the Anglo-French Concorde and Soviet Tupolev Tu-144 entering service during the 1970s, but they proved uneconomic in practice due to the high fuel consumption at supersonic speeds. The associated pollution and sonic boom from these aircraft also raised awareness of the Environmental impact of aviation, making it difficult to find countries prepared to tolerate them. Many other advances took place during this period, such as the introduction of the helicopter, development of the fabric Rogallo wing for sport flying and the reintroduction of the canard or "tail-first" configuration by the Swedish Saab Viggen jet fighter.
Aircraft
Supersonic flight Designers already knew that as an aircraft approaches the speed of sound (Mach 1), in the transonic region, shock waves begin forming, causing a large increase in drag. Wings, already thin, had to become thinner and finer. Fineness is a measure of how thin the wing is compared to its front-to-back chord. A small, highly loaded wing has less drag and so some early types used this type, including the Bell X-1 rocket plane and the Lockheed F-104 Starfighter. But these craft had high takeoff speeds, the Starfighter causing significant pilot deaths during takeoff, and small wings fell out of use. An approach pioneered by German designers during the war was to sweep the wing at an angle, delaying the buildup of shock waves. But this made the wing structure longer and more flexible, making the aircraft more likely to suffer from bending or aeroelasticity and even causing a reversal in the action of the flight controls. Stall behaviour of the swept wing was also poorly understood and could be extremely sharp. Other problems included divergent oscillations which could build up lethal forces. In researching these effects, many pilots lost their lives, for example all three examples of the de Havilland DH.108 Swallow broke up in the air, killing their pilots. while another survived only because he lowered the seat so that, when violent oscillations developed, he did not bang his head on the canopy and break his neck. The triangular delta wing has a swept leading edge while maintaining a sufficiently deep wing root for structural stiffness, and from the introduction of the French Dassault Mirage fighter it became a popular choice, with or without a tailplane. But the plain delta wing proved less manoeuvrable in combat than a more conventional tapered wing, and as time progressed became more heavily modified, with tailed, cropped, double-delta, canard and other forms appearing. As speed increases and becomes fully supersonic, the wing centre of lift moves backwards, causing a change in longitudinal trim and a pitching-down tendency known as Mach tuck. Supersonic aircraft had to be made capable of adjusting sufficiently, in order to maintain adequate control at all stages of flight. Above speeds of around Mach 2.2 the airframe starts to heat up with the friction of the air, causing both thermal expansion and loss of strength in the cheap, easily workable light alloys used for lower speeds. Also, jet engines begin to reach their limits. The Lockheed SR-71 Blackbird was constructed of titanium alloy, had a special corrugated skin to absorb thermal expansion and dual-cycle turbofan-ramjet engines which ran on a special temperature-tolerant fuel. Mach tuck was reduced through the use of long "chine" extensions of the wing along the fuselage, which contributed greater lift at supersonic speeds. Another problem with supersonic flight proved to be its environmental impact. A large aircraft creates a loud shock wave or "sonic boom," which can disturb or damage anything it passes over, while the high drag results in high fuel consumption and consequent pollution. These issues became highlighted with the introduction of the Concorde supersonic transport.
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