Dynamic Stability and Control: Methods and Developments

Abstract

The purpose of this work is to assess the overall usage, evaluation, and understanding of damping derivatives with a focus on accuracy needs and computational efficiency. With the increased usage of neutrally stable and/or complex airframes, there is increasing desire within the aerospace community to improve the accuracy and understanding of such terms in order to assess the overall flight performance of a vehicle. The current state of the art for damping derivative computations includes the use of semi-empirical methods based on limited simple configuration experimental data or the use of time intensive computational fluid dynamic (CFD) studies. This work proposes that the methodologies used for the calculation of damping derivatives focus on the sensitivity of the system in question to the overall accuracy of the terms. In particular for preliminary configuration work, more accurate but less computationally intensive approaches are desired. A study of the equations of motion has been used to assess the general impacts of damping derivative accuracies for flight vehicles. With the accuracy requirements and sensitivities in mind, new methods and usages have been proposed and developed for the expeditious calculation of these terms in the supersonic flight regime. Theoretical and semi-empirical approaches are presented under the assumption that pitch and roll rates are quite small, resulting in quasi-steady aerodynamic analysis. The use of a component synthesis approach to computing full configuration damping derivatives has been developed as a viable, accurate and expedient approach. Slender body theory damping derivative methodologies have been extended into the supersonic regime to calculate the pitch damping derivatives with improved accuracy. In addition, Evvard’s theory has been developed as a compelling approach for determining lifting surface damping derivatives in supersonic flight with sufficient fidelity, flexibility, and expediency for use in conceptual, preliminary and in some cases final design applications for missile systems. Traditional prediction methodologies, such as semi-empirical codes, CFD, and experimental methods are discussed as comparisons to the new approaches developed in this work. Focus is given to supersonic, low angle of attack configurations with explanations and limitations to the various approaches. The result of this work is a novel, efficient preliminary design approach for accurately estimating damping derivatives on a variety of configurations. The work increases the methods available to aerospace community for the calculation of damping derivatives while illustrating the appropriateness of the various tools for the accuracy required.