What typically happens to the center of gravity (CG) during a solid rocket motor's thrusting phase?

During the thrusting phase of a solid rocket motor, the center of gravity (CG) typically shifts forward. This is primarily due to the consumption of propellant. As the motor burns fuel, the mass of the rocket decreases, and the change in mass distribution can often lead to a forward movement of the CG.

In rocketry, the CG is the point where the mass of the rocket is balanced. When a solid rocket motor ignites, it burns fuel from the rear of the rocket, and as that mass is consumed, the overall weight of the rocket decreases. Since the propellant is situated towards the rear, as it burns away, the remaining mass (which includes the payload and rocket structure) becomes relatively more concentrated towards the front of the rocket. This shift increases stability during flight because having the CG forward of the center of pressure (CP) helps the rocket maintain a stable flight path.

Understanding this behavior is crucial for rocket design and performance, as the position of the CG influences how the rocket will fly, including aspects such as stability and recovery. Therefore, recognizing that the CG shifts forward during the thrusting phase is critical for anyone involved in rocketry, particularly in the context of designing and launching solid rocket motors.