SUPERSONIC FLIGHT - Supersonic Jet (speed of sound)
Shock Waves When an airplane moves relatively slowly, air pressure disturbances move faster than the airplane and are able to disperse. However, when an airplane moves faster than the speed of sound, air pressure disturbances are unable to disperse; instead, they amass in front of the airplane. A cone-shaped shock wave forms, audible to those on the ground as a sonic boom.
In addition to balancing lift, weight, thrust, and drag, modern airplanes have to contend with another phenomenon. The sound barrier is not a physical barrier but a speed at which the behavior of the airflow around an airplane changes dramatically. Fighter pilots in World War II (1939-1945) first ran up against this so-called barrier in high-speed dives during air combat. In some cases, pilots lost control of the aircraft as shock waves built up on control surfaces, effectively locking the controls and leaving the crews helpless. After World War II, designers tackled the realm of supersonic flight, primarily for military airplanes, but with commercial applications as well. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)
Concorde Airplane Distinguished by a pointed nose that angles downward during takeoff, the Anglo-French Concorde flies at more than twice the speed of sound. The delta-winged plane was co-developed by Britain and France and began passenger service in 1976. Controversy has surrounded its use in the United States; the supersonic plane is very noisy, and some believe its sonic booms harm the environment. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)
Supersonic flight is defined as flight at a speed greater than that of the local speed of sound. At sea level, sound travels through air at approximately 1,220 km/h (760 mph). At the speed of sound, a shock wave consisting of highly compressed air forms at the nose of the plane. This shock wave moves back at a sharp angle as the speed increases. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)
B-1B Bomber The United States Air Force contracted with Rockwell International to build the B-1 in 1970 as a manned strategic bomber. After President Jimmy Carter halted the plane’s development in 1977, President Ronald Reagan revived the program as the B-1B in 1981. The B-1B, which costs $250 million per plane, features the swing-wing, which allows it to fly at both slow speeds and supersonic speeds. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)
Supersonic flight was achieved in 1947 for the first time by the Bell X-1 rocket plane, flown by Air Force test pilot Chuck Yeager. Speeds at or near supersonic flight are measured in units called Mach numbers, which represent the ratio of the speed of the airplane to the speed of sound as it moves air. An airplane traveling at less than Mach 1 is traveling below the speed of sound (subsonic); at Mach 1, an airplane is traveling at the speed of sound (transonic); at Mach 2, an airplane is traveling at twice the speed of sound (supersonic flight). Speeds of Mach 1 to 5 are referred to as supersonic; speeds of Mach 5 and above are called hypersonic. Designers in Europe and the United States developed succeeding generations of military aircraft, culminating in the 1960s and 1970s with Mach 3+ speedsters such as the Soviet MiG-25 Foxbat interceptor, the XB-70 Valkyrie bomber, and the SR-71 spy plane.In 2004 the experimental X-43 plane smashed previous airplane speed records by flying at nearly Mach 10. The unpiloted craft was constructed by the National Aeronautics and Space Administration (NASA).
NASA's experimental plane, the X-43, smashed speed records in 2004. Powered by a scramjet engine, the unpiloted plane flew at Mach 9.6, nearly ten times the speed of sound.
The shock wave created by an airplane moving at supersonic and hypersonic speeds represents a rather abrupt change in air pressure and is perceived on the ground as a sonic boom, the exact nature of which varies depending upon how far away the aircraft is and the distance of the observer from the flight path. Sonic booms at low altitudes over populated areas are generally considered a significant problem and have prevented most supersonic airplanes from efficiently utilizing overland routes. For example, the Anglo-French Concorde, a commercial supersonic aircraft, is generally limited to over-water routes, or to those over sparsely populated regions of the world. Designers today believe they can help lessen the impact of sonic booms created by supersonic airliners but probably cannot eliminate them. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)
One of the most difficult practical barriers to supersonic flight is the fact that high-speed flight produces heat through friction. At such high speeds, enormous temperatures are reached at the surface of the craft. In fact, today’s Concorde must fly a flight profile dictated by temperature requirements; if the aircraft moves too fast, then the temperature rises above safe limits for the aluminum structure of the airplane. Titanium and other relatively exotic, and expensive, metals are more heat-resistant, but harder to manufacture and maintain. Airplane designers have concluded that a speed of Mach 2.7 is about the limit for conventional, relatively inexpensive materials and fuels. Above that speed, an airplane would need to be constructed of more temperature-resistant materials, and would most likely have to find a way to cool its fuel. (SUPERSONIC FLIGHT - Supersonic Jet speed of sound)