Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
Mach Five protagonists build the Mach 6. The Mach 6's engine is not designed to run on gas, which is a crucial story point, even though gas is still used for it through most of the series. It has all the features of the Mach Five, but redesigned or changed in some form or another. For example, the rotary saws are kept, but they're turned into laser saws, and the blades can pivot so things that are over head can be cut. The new car features a transparent, holographic screen over the dashboard that the driver can use to interact live with