Supersonic speed

Supersonic travel is a rate of travel of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 344 m/s, 1,125 ft/s, 768 mph, 667 knots, or 1,235 km/h. Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.At the beginning of the 20th century, the term 'supersonic' was used as an adjective to describe sound whose frequency is above the range of normal human hearing. The modern term for this meaning is 'ultrasonic'. The tip of a bullwhip is thought to be the first man-made object to break the sound barrier, resulting in the telltale 'crack' (actually a small sonic boom). The wave motion traveling through the bullwhip is what makes it capable of achieving supersonic speeds.To date, only one land vehicle has officially travelled at supersonic speed. It is ThrustSSC, driven by Andy Green, which holds the world land speed record, having achieved an average speed on its bi-directional run of 1,228 km/h (763 mph) in the Black Rock Desert on 15 October 1997.Supersonic aerodynamics is simpler than subsonic aerodynamics because the airsheets at different points along the plane often cannot affect each other. Supersonic jets and rocket vehicles require several times greater thrust to push through the extra aerodynamic drag experienced within the transonic region (around Mach 0.85–1.2). At these speeds aerospace engineers can gently guide air around the fuselage of the aircraft without producing new shock waves, but any change in cross area farther down the vehicle leads to shock waves along the body. Designers use the Supersonic area rule and the Whitcomb area rule to minimize sudden changes in size.