max q

The max q, or maximum dynamic pressure, condition is the point when an aerospace vehicle's atmospheric flight reaches the maximum difference between the fluid dynamics total pressure and the ambient static pressure. For an airplane, this occurs at the maximum speed at minimum altitude corner of the flight envelope. For a space vehicle launch, this occurs at the crossover point between dynamic pressure increasing with speed and static pressure decreasing with increasing altitude. This is an important design factor of aerospace vehicles, since the aerodynamic structural load on the vehicle is proportional to dynamic pressure. Dynamic pressure Dynamic pressure q is defined in incompressible fluid dynamics as where ρ is the local air density, and v is the vehicle's velocity. The dynamic pressure can be thought of as the kinetic energy density of the air with respect to the vehicle, and for incompressible flow equals the difference between total pressure and static pressure. This quantity appears notably in the lift and drag equations. For a car traveling at at sea level (where the air density is about ,) the dynamic pressure on the front of the car is , about 0.38% of the static pressure ( at sea level).