Aerodynamic estimation techniques for aerostats and airships

A semi-empirical steady-state model of a finned axisymmetric body is developed and used to compute hull -fin mutual interference factors and cross flow drag coefficients from wind tunnel data on five aerostats and airships. The results are in general agreement with expectations from theory and provide a b asis for predicting aerodynamic coefficients. The model is extended to unsteady motion by considering the local flow on finite hull segments and the fins. This dynamic model is applicable to non-linear simulations and the computation of rotational stability derivatives for which equations are derived. For one zerostat, rotational stability derivatives calculated from static wind tunnel data are compared with experimental results from a whirl ing-arm tow tank.