What is the stability "rule-of-thumb" for rockets?

The stability "rule-of-thumb" for rockets emphasizes the importance of the relationship between the center of gravity (CG) and the center of pressure (CP). When the center of gravity is at least one body diameter in front of the center of pressure, it ensures that the rocket has a stable flight path.

In simpler terms, this configuration helps to keep the rocket oriented properly during ascent. If the CG is too far back (behind the CP), the rocket can become unstable, leading to erratic flight patterns or even potential failure. This rule is based on the principles of aerodynamics and dynamics, which dictate how forces act on an object in motion.

By ensuring the CG is ahead of the CP, you create a restoring effect when disturbances occur; the rocket will naturally want to return to its stable orientation rather than veering off course. This characteristic is crucial for controlled and successful rocket launches, contributing to predictable and efficient performance during flight.