Erroneous news reports caused most people to envision the sound barrier as a physical "wall", which supersonic aircraft needed to "break" with a sharp needle nose on the front of the fuselage. A similar problem is thought to have been the cause of the 1943 crash of the BI-1 rocket aircraft in the Soviet Union.Īll of these effects, although unrelated in most ways, led to the concept of a "barrier" making it difficult for an aircraft to exceed the speed of sound. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of a de Havilland Swallow and death of its pilot Geoffrey de Havilland, Jr. Worse still, a particularly dangerous interaction of the airflow between the wings and tail surfaces of diving Lockheed P-38 Lightnings made "pulling out" of dives difficult however, the problem was later solved by the addition of a "dive flap" that upset the airflow under these circumstances. This was solved in later models with changes to the wing. ![]() Likewise, the flexing caused by the low torsional stiffness of the Supermarine Spitfire's wings caused them, in turn, to counteract aileron control inputs, leading to a condition known as control reversal. In this case, several attempts to fix it only made the problem worse. Flying the Mitsubishi Zero, pilots sometimes flew at full power into terrain because the rapidly increasing forces acting on the control surfaces of their aircraft overpowered them. Unfortunately, doing so led to numerous crashes for a variety of reasons. Nevertheless, propeller aircraft were able to approach their critical Mach number, different for each aircraft, in a dive. The whirling blades in the front of the jet engine are not adversely affected by high aircraft speeds in the same way as the propeller. It produces the required power, in terms of thrust, from a relatively small size compared to the piston engine it replaced. The jet engine is suitable for two reasons. This speed limitation led to research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany. To fly faster, the engine power required to replace this loss, as well as to equal the increasing aircraft drag with speed, is so great that the size and weight of the engine becomes prohibitive. Shock waves form at the blade tips and reduce how much of the shaft power driving the propeller is converted into the thrust force needed to move the aircraft. When the aircraft speed is high enough, the tips reach supersonic speeds. The tip speed of propeller blades depends on the propeller speed and the forward speed of the aircraft. Meteorites in the Earth's upper atmosphere usually travel at higher than Earth's escape velocity, which is much faster than sound. This finding is theoretical and disputed by others in the field. Some paleobiologists report that computer models of their biomechanical capabilities suggest that certain long-tailed dinosaurs such as Brontosaurus, Apatosaurus, and Diplodocus could flick their tails at supersonic speeds, creating a cracking sound. The sound barrier may have been first breached by living beings about 150 million years ago. ![]() Firearms made after the 19th century generally have a supersonic muzzle velocity. Some common whips such as the bullwhip or stockwhip are able to move faster than sound: the tip of the whip exceeds this speed and causes a sharp crack-literally a sonic boom. By the 1950s, new designs of fighter aircraft routinely reached the speed of sound, and faster. In 1947, American test pilot Chuck Yeager demonstrated that safe flight at the speed of sound was achievable in purpose-designed aircraft, thereby breaking the barrier. These difficulties represented a barrier to flying at faster speeds. The term came into use during World War II when pilots of high-speed fighter aircraft experienced the effects of compressibility, a number of adverse aerodynamic effects that deterred further acceleration, seemingly impeding flight at speeds close to the speed of sound. Flying faster than sound produces a sonic boom. The term sound barrier is still sometimes used today to refer to aircraft approaching supersonic flight in this high drag regime. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster speeds very difficult or impossible. The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound.
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