Supersonic
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- For other uses, see Supersonic (disambiguation)}}}.
Sounds are vibrations in an elastic medium. In gases sound travels longitudinally at different speeds, mostly depending on the molecular mass and temperature of the gas; whilst pressure has a much smaller effect. Since air temperature and composition varies significantly with altitude, mach numbers for aircraft are related to the speed of sound at sea level. In water at room temperature supersonic can be considered as any speed greater than 1,440 m/s or 4,724 ft/s. In solids, sound waves can be longitudinal or transverse and have even higher velocities.
Supersonic fracture is crack motion faster than the speed of sound in a brittle material. This phenomenon was first discovered by scientists from the Max Planck Institute for Metals Research in Stuttgart (Markus J. Buehler and Huajian Gao) and IBM Almaden Research Center in San Jose, California (Farid F. Abraham).
Supersonic objects
Many modern fighter aircraft are supersonic. The Concorde and Tupolev Tu-144 were supersonic passenger aircraft. But, since Concorde's final retirement flight on November 26 2003, there are no supersonic passenger aircraft left in service. Some large bombers, such as the Tupolev Tu-160 and Rockwell/Boeing B-1B are also supersonic-capable.
Most modern firearm munitions are supersonic, with rifle projectiles often travelling at speeds approaching Mach 3.
Most spacecraft, most notably the Space Shuttle are supersonic at least during portions of their reentry, even though most of their reentry flight time is considered hypersonic.
Breaking the sound barrier
In 1942 the United Kingdom's Ministry of Aviation began a top secret project with Miles Aircraft to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype Miles M.52 jet aircraft, which was designed to reach 1,000 mph (1,600 km/h) at 36,000 feet (11 km) in 1 minute 30 seconds.
The aircraft's design was revolutionary introducing many innovations which are still used on today's supersonic aircraft. The single most important development was the all-moving tailplane giving extra control to counteract the Mach tuck which allowed control to be maintained at supersonic speeds; this was the brainchild of Dennis Bancroft and his team at Miles Research. The project was cancelled by the Director of Scientific Research, Sir Ben Lockspeiser, before any manned fights were conducted. Subsequently, on government orders, all design data and research regarding the Miles M.52 was sent to BELL aircraft in the USA. There was an agreement for data exchange in both directions, but allegedly, after receiving the British data, the American government blocked the deal. Later experimentation on the Miles M.52 design proved that the aircraft would indeed have broken the sound barrier, with an unmanned 3/10 scale replica of the M.52 achieving Mach 1.5 in October 1948.
George Welch made a plausible but unverified claim to have broken the sound barrier on October 1, 1947 while flying an F-86 Sabre. He also claimed to have repeated his supersonic flight on October 14 1947, 30 minutes before Chuck Yeager broke the sound barrier in the Bell X-1, using the adjustable tail concept.
Chuck Yeager was the first man to break the sound barrier in level flight on October 14 1947, flying the experimental Bell X-1 at Mach 1 at an altitude of 45,000 feet (13.7 km).
Hans Guido Mutke claimed to have broken the sound barrier before Yeager, on April 9 1945 in a Messerschmitt Me 262. However, this claim is widely disputed.
A team led by Richard Noble and driver Andy Green became the first to break the sound barrier in a land vehicle, called the ThrustSSC ("Super Sonic Car"), on October 15 1997, almost exactly 50 years after Yeager's flight.
Supersonic aerodynamics
Supersonic aerodynamics are simpler than subsonic because the airsheets at different points along the plane often can't affect each other. Supersonic jets and rocket vehicles require several times greater thrust to push through the extra drag experienced within the transonic region (around Mach 0.85-1.5).
Aerospace engineers can gently guide air around the fuselage of the aircraft without producing new shock waves but any change in cross sectional area further down the vehicle leads to shock waves along the body. Designers use the Whitcomb area rule and minimize sudden changes in size.
Nasa has recently shown that a bow shock wave widens and flattens before it reaches the ground, while multiple shocks produce N-waves with a lot of energy in the audio range. As internal supersonic compression can unstart, designers want external compression. As these produce also external shocks, they have to be located at the nose.
It should be kept in mind, however, that the aerodynamic principles behind a supersonic aircraft are often more complex than described above due to the fact that such an aircraft must be efficient and stable at supersonic, transonic and subsonic flight.
At high speeds aerodynamic heating can occur, so an aircraft must be designed to operate and function under very high temperatures. For example, the SR-71 Blackbird jet could fly continuously at Mach 3.1 while some parts were above 600F (315C).
See also
- Aerodynamics#Supersonic aerodynamics
- De Laval nozzle
- Jet engine#Air intake design
- Jet engine#Nozzle
- Mach number
- Rocket engine nozzles
- Sonic boom
- Sound barrier
- The Right Stuff a movie about early * Whitcomb area rule
External links
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