Experimental Verification of the USAFA 1-DOF Dynamic Stability Characterization Capability and Future 3-DOF Cross Coupling Enhancements

Abstract

In order to provide a cost-effective and responsive method of dynamic stability analysis for the NASA Johnson Space Center, the United States Air Force Academy (USAFA) developed and validated a One Degree of Freedom (1-DOF) Evaluation Technique over the past several years. The technique was initially applied to the NASA Orion Crew Module but was successfully expanded to aircraft applications for the first time during this effort. The validation of the USAFA Technique for aircraft applications necessitated both an experimental and computational investigation of its capabilities in evaluations of aerodynamic and stability characteristics. To accomplish this objective, a NASA-developed Standard Dynamics Model (SDM) that has consistently been used as part of an international effort to compile stability data was chosen for comprehensive testing. After more than 20 hours of wind tunnel testing in the USAFA Aeronautics Laboratory subsonic wind tunnel and 200,000 hours of simulations run on the Onyx super-computing cluster, the USAFA 1-DOF technique was validated with confidence for aircraft applications. Similarities between the experimental results of the technique and prior experimentation at the Arnold Engineering Development Center (AEDC) provided confidence in the successful transition of the technique to aircraft applications, and the Computational Fluid Dynamics (CFD) study further explained the complex flow physics surrounding the SDM during experimental testing. Ultimately, the successful expansion of the USAFA 1-DOF Dynamic Stability Evaluation Technique to aircraft applications has provided a viable, efficient, and effective alternative to traditionally expensive and time-intensive testing for flight vehicle stability analysis. The technique further enables rapid prototyping and design of flight vehicles via digital engineering. However, there was a concern with flow interference effects between the 1-DOF vertical mounting rod and the vertical tail of aircraft. This success and concern directly led to the development of the USAFA’s Dynamic Pitch Mechanism (DPM), a revolutionary testing rig that further pushes the envelope of the USAFA’s evaluation capabilities into three degrees of freedom, identification of coupling effects, and elimination of mounting rod interference. DISTRIBUTION STATEMENT A: Approved for public release: distribution unlimited. PA NUMBER: USAFA-DF-2022-48 DISCLAIMER: The views expressed in this article, book, or presentation are those of the authors and do not necessarily reflect the official policy or position of the United States Air Force Academy, the Air Force, the Department of Defense, or the U.S. Government.