Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
Bluebird Mach 1.1 Bluebird Mach 1.1 Bluebird Mach 1.1 (CMN-8) was a design for a rocket-powered supersonic land speed record car, planned by Donald Campbell but thwarted by his subsequent death during a water speed record attempt in "Bluebird K7" in early 1967. Donald Campbell decided a massive jump in speed was called for following his successful 1964 LSR attempt in "Bluebird CN7". His vision was of a supersonic rocket car with a potential maximum speed of 840 mph, referred to as "Bluebird Mach 1.1". Norris Brothers were requested to undertake a design study. Campbell, ever superstitious, chose a lucky date to hold