Below what altitudes do shock waves form? For a shock wave to form, the air must have a certain density. Surely in Thermosphere or even upper parts of Mesospheres the air is very thin. I was wondering if there is a formula related to the Mach Number and the probability of shock wave.
Shock waves form any time the speed of the airflow over or around a vehicle exceeds the speed of sound.
The local speed of sound varies with ambient temperature in a well-defined way; in general it goes down slightly as you climb higher.