Contraj 7DOF Important Note on Aero Tables

For this tutorial both aero predictors, Spinner and Finner, will be used to predict the aerodynamics of the example projectile. It is important for the user to understand these Aeros. The tutorial will have the user modifying the aerodynamics in the Fin Aeros table which Contraj utilizes to build up the full aerodynamics State within Contraj. This tutorial also has the user modify the Basic Aeros table within the Aero direct input module to reflect the full state of the aerodynamics.

Since the aerodynamics in the basic Aeros are used by the Stability module it is very important the user knows how to modify this table. The basic Aeros table represents the aerodynamic state of having 4 fins on the nose instead of 2 in this example. This specifically affects the Gyroscopic Stability calculation. Within CONTRAJ the aerodynamics are split in to the Alpha Plane and the Beta plane (Pitch and Yaw). When modeling two fins as in this example the Aeros in the Alpha Plane (CMA, CNA and CMQ ) include the two fins on the nose. The beta plane will only show the full body Aeros without the fins. (If 4 fins were modeled the aerodynamic tables would match).

In reality since the rear of the projectile will still be spinning the gyroscopic stability would be a blend between the alpha and beta planes and the Gyroscopic Stability factor shown in the tabular output would be a blend of the two planes. The user should verify that the round is gyroscopically stable in both planes especially in the alpha plane which will represent the roll orientation of the fins on the nose.