Soil simulant preparation for lunar deep drilling exploration: Modeling and validation

In order to enhance the understanding of the planet's geological evolution and determine whether there exists liquid water, solid ice or any other life evidence, plenty of extraterrestrial explorations have been attempted over the past decades. For future planetary drilling missions, especially unmanned drilling tasks, the autonomous drilling activity should be first verified. In order to replicate the geological formations encountered in the lunar drilling process, large amounts of lunar soil simulant are required. This simulant must be prepared at controlled densities in order to mimic the true mechanical behavior of real lunar soils. Herein, a tamping based dense soil simulant preparation method is proposed. Taking hammer's rebounding, soil's plastic-elastic deformation, and simulant's effective dense height into consideration, a novel theoretical tamping model has been established to predict the preparation parameters. Verification tests showed that the theoretical model correctly predicts the experimentally observed trend in the tamping force with the number of cycles and the optimized relative density of simulant over 180 mm depth from the top is close to that of the real deep lunar soil.