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The supersonic speed range is that range of speeds within which all of the airflow over an aircraft is supersonic (more than Mach 1). But airflow meeting the leading edges is initially decelerated, so the free stream speed must be slightly greater than Mach 1 to ensure that all of the flow over the aircraft is supersonic.
It's often used colloquially to mean "very fast" (see also: Sonic the Hedgehog). However, there are some major differences between supersonic and hypersonic flight. Here's what each term really...
Typically, we measure the speed of an aircraft by its Mach number, which is a velocity relative to the speed of sound (approximately 770 mph or 1,239 kmh at sea level). Mach 1 is the speed of sound. Four general categories define the speed of flight: subsonic, transonic, supersonic and hypersonic. Each is relative to a Mach number.
Hypersonic and supersonic are both terms used to describe speeds faster than the speed of sound, but they differ in their specific velocity ranges. Supersonic refers to speeds that are faster than the speed of sound, which is approximately 343 meters per second or 767 miles per hour.
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.
Supersonic flight requires 3-4 times more fuel than subsonic flight. Hypersonic flight could require up to 6 times more fuel per passenger. Operating costs scale up rapidly.
Hypersonic and Supersonic are terms primarily used in aerodynamics to describe specific speed ranges relative to the speed of sound. The speed of sound, referred to as Mach 1, is roughly 767 mph at sea level. Supersonic speeds are those that exceed Mach 1 but are less than Mach 5.
For speeds greater than five times the speed of sound, M > 5, the flow is said to be hypersonic. At these speeds, some of the energy of the object now goes into exciting the chemical bonds which hold together the nitrogen and oxygen molecules of the air.
Understand the differences between swept wings with subsonic and supersonic leading edges. Understand the principle of vortex lift creation on slender delta wings at high angles of attack. Appreciate some of the challenges in the engineering and operations of a supersonic transport airplane (SST).
Hypersonic speed is five times the speed of sound. Scientists measure speeds this fast with a Mach number, named for Austrian physicist Ernst Mach. Sound has a speed of Mach 1 and anything Mach 5 or above is considered hypersonic.