NASA's Apollo 12 mission provided evidence that lunar dust, accelerated by the exhaust plumes of landing spacecraft, is capable of causing erosive wear damage to nearby lunar structures. During Apollo 12, the Surveyor III lunar probe was "sandblasted" by lunar dust particles advected by the exhaust plume of the Lunar Lander. The low gravitational field of the Moon and the negligible atmospheric drag mean that such lunar dust is able to travel unimpeded for long distances. As a result, lunar structures located far from the spacecraft's landing site are susceptible to such erosive wear damage. In particular, optical instruments, such as lenses and mirrors, and thermal devices, such as radiators, can be severely affected by such particle impingement. Though the particles may not remove much material, their impacts change the object's surface characteristics which, in previous works, the authors have proven can lead to significant changes in reflectance and transmittance. The experimental investigations the authors have done on this subject in previous works with the JSC-1AF lunar dust simulant has been used to validate the computational model in the current work. The model uses the discrete element method (DEM) and computational fluid dynamics (CFD) to predict the motion and impingement of the lunar dust particles. In this study, lunar dust erosive wear of steel, aluminum and acrylic surfaces, and the effect of 30° and 90° impact angles were simulated. A Hertzian contact formulation was used to predict the indentation of the particles into the surface. It was found that the modeling approach is very well-suited to quantitatively predict the erosive wear on the materials simulated. The results from the model agreed with the experiments in the volume of material removed. Also, the shape of the particle impact region matched very well to the experiments. Such physics-based, quantitative modeling approaches for this phenomenon are important as they can help to indentify methods and materials which may be used to mitigate the effects of lunar dust erosive wear. Modeling can also be helpful for obtaining information about low-gravity, thermally-extreme environments which may be challenging to access experimentally. The Moon will see an unprecedented number of lunar landings in the next few years. The exhaust-blown dust by these spacecraft may be become a significant factor affecting the ability for these missions to succeed.
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