Why are most APCP rocket motors considered to be central burning?

Most APCP rocket motors are classified as central burning because they utilize a design that allows for a controlled and steady combustion of the propellant from the center outwards. This characteristic can result from the chemical composition and the physical arrangement of the propellant grain, which often leads to a burn rate that is too low for an end-burner configuration to be effective.

The central burning design is especially advantageous for achieving a consistent thrust over the burn duration, which is critical for maintaining stability and performance during flight. By burning from the center, the available surface area of the propellant is utilized effectively throughout the burn, allowing for a prolonged and reliable thrust output.

In contrast, other configurations, such as end-burners, typically rely on higher burn rates that may not be achievable with the propellant formulations used in Central burning APCP motors. Thus, the classification as central burning is primarily due to the specific burn characteristics that influence thrust production and efficiency in these rocket motors.