As an aircraft moves through the air, the air molecules near the
aircraft are disturbed and move around the aircraft.
Exactly how the air re-acts to the aircraft depends upon the
ratio of the speed of the aircraft to the
speed of sound through the air.
Because of the
importance of this speed ratio, aerodynamicists have designated it
with a special parameter called the
in honor of Ernst Mach, a late 19th century physicist who studied gas
For aircraft speeds which are greater than the speed of sound,
the aircraft is said to be supersonic.
Typical speeds for supersonic aircraft are greater than 750 mph
but less than 1500 mph, and the
Mach number M is greater than one, 1 < M < 3.
In supersonic flight, we encounter
and the local
varies because of
The first powered aircraft to explore this regime was the
Bell X-1A, in 1947. It and subsequent experimental aircraft
proved that humans could fly supersonically.
The aerodynamics of these early aircraft is used on
modern supersonic fighter aircraft. There have been several
efforts to develop cost-effective supersonic airliners.
The Russian TU-144 and the Anglo-French Concorde went into
service in the early 1970's but were financial failures.
Because of the high
associated with supersonic flight, fighter aircraft
propulsion systems. On the
slide we show an F-14 which is powered by two
afterburning turbofan engines. The
of supersonic fighters are
in planform to reduce drag.
The F-14 is unique because the amount of sweep can be
varied by the pilot; low sweep for good low speed performance, high
sweep for supersonic flight.
For Mach numbers less than 2.5, the frictional heating of
the airframe by the air is low enough that
light weight aluminum is used for the structure.
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