In order to test the simplified methods, five identical model rockets were built except with varying fin heights. Reducing the fin height moves the CP forward. The CG and the CP (using four methods) were measured for the five rockets. In addition, the Swing Test was performed. Each method predicted a different degree of stability for each rocket. After noting what the methods predicted, each of the rockets was launched multiple times to see which ones were stable and which were not. The actual stability of the rockets, based on observing the launches, was compared to the predicted stability of the different methods.
For all five of the rockets, the launches tended to be more stable than the methods predicted.
The results showed that the common methods of determining rocket stability are too conservative, in light wind conditions. Rockets that should have been unstable, according to the models, had stable flights. Only one method, the Complete Barrowman Equations, was a reliable predictor of stability.
This project tested whether the common methods of determining the center of pressure in relationship to the center of gravity of a model rocket are reliable indicators of its stability.
Science Fair Project done By Robert G. Wright