Critical Mach number Critical Mach number In aerodynamics, the critical Mach number (Mcr or M* ) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it. At the lower critical Mach number, airflow around the entire aircraft is subsonic. At the upper critical Mach number, airflow around the entire aircraft is supersonic. For an aircraft in flight, the speed of the airflow around the aircraft differs considerably in places from the airspeed of the aircraft; this is due to the airflow having to speed up
Mach Five "Mach 6", two different single-seater cars created specifically for stunt races. The designs of the Mach 4 and Mach 6 are vaguely reminiscent of the Mach Five's (as in the original American comics), although the only functions the Mach 6 features are the jump jacks, which are standard equipment in race cars in the movie. Little about the Mach 4 is known, as it appears only briefly in the film and is portrayed as a red-colored companion to the 6. The film portrays the Mach Five as initially being a regular everyday vehicle, justifying the existence of its trunk door