I recently purchased a Telsa Model Y Long Range electric vehicle (EV) and wanted a license plate that was fitting for both the car and my personal interests. I am an electrical engineer and a private pilot with interest in aeronautics and space flight. "MAX Q" has ties to both as the letter 'q' is used to represent electric charge in electrical engineering and it is used to represent dynamic pressure in aeronautics.
Electric charge is measured in Coulombs which is the amount of charge that flows at one Ampere in one second. In other words one Ampere is one Coulomb of charge flowing for one second. One Coulomb is about 6×1018 electrons (6 billion billion electrons). So "Max Q" translates to "Max Charge"
Dynamic pressure is the result of an aircraft or rocket moving through air. The speed of the rocket and the density of the air determine the dynamic pressure. At launch a rocket's velocity is low while the air is most dense. As the rocket ascends its velocity increases but the air density decreases with altitude. Somewhere in between these extremes the dynamic pressure on the rocket reaches its maximum - "Max Q"
For more information please see the following web sites: