Maggie Sunseri Biography & Facts
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. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster speeds very difficult or impossible. The term sound barrier is still sometimes used today to refer to aircraft approaching supersonic flight in this high drag regime. Flying faster than sound produces a sonic boom.
In dry air at 20 °C (68 °F), the speed of sound is 343 metres per second (about 767 mph, 1234 km/h or 1,125 ft/s). 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. These difficulties represented a barrier to flying at faster speeds. 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. By the 1950s, new designs of fighter aircraft routinely reached the speed of sound, and faster.
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. Firearms made after the 19th century generally have a supersonic muzzle velocity.The sound barrier may have been first breached by living beings about 150 million years ago. Some paleobiologists report that, based on computer models of their biomechanical capabilities, certain long-tailed dinosaurs such as Brontosaurus, Apatosaurus, and Diplodocus may have been able to flick their tails at supersonic speeds, creating a cracking sound. This finding is theoretical and disputed by others in the field.
Meteors entering the Earth's atmosphere usually, if not always, descend faster than sound.
The tip speed of propeller blades depends on the propeller speed and the forward speed of the aircraft. When the aircraft speed is high enough, the tips reach supersonic speeds. 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. 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. This speed limitation led to research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany. The jet engine is suitable for two reasons. It produces the required power, in terms of thrust, from a relatively small size compared to the piston engine it replaced. 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.
Nevertheless, propeller aircraft were able to approach their critical Mach number, different for each aircraft, in a dive. Unfortunately, doing so led to numerous crashes for a variety of reasons. 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. In this case, several attempts to fix it only made the problem worse. 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. This was solved in later models with changes to the wing. 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. 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. on 27 September 1946. A similar problem is thought to have been the cause of the 1943 crash of the BI-1 rocket aircraft in the Soviet Union.
All 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. 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. Rocketry and artillery experts' products routinely exceeded Mach 1, but aircraft designers and aerodynamicists during and after World War II discussed Mach 0.7 as a limit dangerous to exceed.
During WWII and immediately thereafter, a number of claims were made that the sound barrier had been broken in a dive. The majority of these purported events can be dismissed as instrumentation errors. The typical airspeed indicator (ASI) uses air pressure differences between two or more points on the aircraft, typically near the nose and at the side of the fuselage, to produce a speed figure. At high speed, the various compression effects that lead to the sound barrier also cause the ASI to go non-linear and produce inaccurately high or low readings, depending on the specifics of the installation. This effect became known as "Mach jump". Before the introduction of Mach meters, accurate measurements of supersonic speeds could only be made remotely, normally using ground-based instruments. Many claims of supersonic speeds were found to be far below this speed when measured in this fashion.
In 1942, Republic Aviation issued a press release stating that Lts. Harold E. Comstock and Roger Dyar had exceeded the speed of sound during test dives in a Republic P-47 Thunderbolt. It is widely agreed that this was due to inaccurate ASI readings. In similar tests, the North American P-51 Mustang demonstrated limits at Mach 0.85, with every flight over M0.84 causing the aircraft to be damaged by vibration.
One of the highest recorded instrumented Mach numbers attained for a propeller aircraft is the Mach 0.891 for a Spitfire PR XI, flown during dive tests at the Royal Aircraft Establishment, Farnborough in April 1944. The Spitfire, a photo-reconnaissance variant, the Mark XI, fitted with an extended "rake type" multiple pitot system, was flown by Squadron Leader J. R. Tobin to this speed, corresponding to a corrected true airspeed (TAS) of 606 mph. In a subsequent flight, Squadron Leader Anthony Martindale achieved Mach 0.92, but it ended in a forced landing after over-revving damaged the engine.Hans Guido Mutke claimed to have broken the sound barrier on 9 April 1945 in the Messerschmitt Me 262 jet aircraft. He states that his ASI pegged itself at 1,100 ki.... Discover the Maggie Sunseri popular books. Find the top 100 most popular Maggie Sunseri books.