The free-flight behavior of entry vehicles can greatly impact vehicle and mission design. Current methodologies rely heavily on ground and flight experiments, while computational fluid dynamics is largely used as a complement to experiments in the form of static aerodynamic databases. The dynamic stability of entry vehicles is primarily studied through ballistic range experiments and flight tests. In an effort to validate the predictive capabilities of computational fluid dynamics for free-flight aerodynamic behavior, numerical simulations of a ballistic range experiment are performed using the unstructured finite-volume Navier-Stokes solver, US3D. The ballistic range tests used for comparison in this paper were performed on a scaled model of the Supersonic Inflatable Aerodynamic Decelerator geometry. The purpose of these experiments was to provide aerodynamic coefficients of the vehicle as an a priori analysis of dynamic stability coefficients ahead of the Supersonic Flight Demonstration Test. The range data span the moderate Mach number range, 3.8-2.0, with a maximum total angle-of-attack range, 10-20 deg. These conditions are intended to span the Mach/angle-of-attack space for the majority of the flight test. Comparisons to raw vehicle attitude and postprocessed aerodynamic coefficients are made between simulated results and experimental data. The resulting comparisons for both the raw model attitude and derived aerodynamic coefficients show good agreement with experimental results. Additionally, near-body pressure field values for each trajectory simulated are investigated. Extracted surface and wake pressure data give further insight into dynamic/flow coupling, leading to a potential mechanism for dynamic instability.
Bibliographical noteFunding Information:
Joseph M. Brock is supported through the NASA Entry Systems Modeling project within the NASA Game Changing Development Program. Contract support was provided through Analytical Mechanics Associates, Inc., under the NNA15BB15C contract. Eric Stern is supported through the NASA Engineering and Safety Center Early Career Engineer Program. The authors gratefully acknowledge Michael Barnhadt, Cole Kazemba, and Jeffrey Brown for their insight into various aspects of this paper.
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