Impact Characterization of Earth Entry Vehicle for Terminal Landing (on Soil)
Shorts, Daniel Calvert
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In order to more accurately predict loads subjected to the EEV (Earth Entry Vehicle) upon impact with a variety of materials, finite element simulations of soil/EEV impact were created using the program LS-DYNA. Various modeling techniques were analyzed for accuracy through comparison with physical test data when available. Through variation of numerical methods, mesh density, and material definition, an accurate and numerically efficient representation of physical data has been created. The numerical methods, Lagrangian, arbitrary Lagrangian-Eulerian (ALE), and spherical particle hydrodynamics (SPH) are compared to determine their relative accuracy in modeling soil deformation and EEV acceleration. Experimentally validated soil material parameters and element formulations were then used in parametric studies to gain a perspective on effects of EEV mass and geometry on its maximum acceleration across varying soil moisture content. Additionally, the effects of EEV orientation, velocity, and impact material were explored. Multi-material arbitrary Lagrangian-Eulerian (MMALE) formulation possess the most effective compromise between its ability to: accurately display qualitative soil behavior, accurately recreate empirical test data, be easily utilized in parametric studies, and to maintain simulation stability. EEV acceleration can be minimized through increase of EEV mass (with constant geometry), allowing for maximum penetration depth, and longest deceleration time. A critical orientation was discovered at 30⁰ from normal, such that maximum EEV surface area impacts the soil surface instantaneously, resulting in maximum acceleration. Off-nominal impact with concrete is predicted to increase acceleration by up to 630% from impact with soil.
- Masters Theses