If a rocket has its center of gravity (CG) four inches behind the center of pressure (CP), is it likely to be stable?

In rocketry, stability is primarily determined by the relationship between the center of gravity (CG) and the center of pressure (CP). The center of gravity is the point where the rocket's mass is balanced, while the center of pressure is the point where aerodynamic forces are balanced. For a rocket to be stable, the CG must be located ahead of the CP.

When the CG is positioned behind the CP, as in the scenario where it is four inches behind, the rocket is prone to instability. This configuration can cause the rocket to oscillate or tumble uncontrollably during flight, as any disturbance in pitch will produce a force that further exacerbates the deviation from its intended flight path.

In stable rockets, a disturbance will create aerodynamic forces that push the rocket back toward its equilibrium position. However, if the CG is behind the CP, those forces will push it further away from its intended trajectory, leading to a loss of control. Therefore, a rocket with the CG located four inches behind the CP is indeed likely to be unstable.