The Study On The Interaction Between Lunar Lander’s Footpad And Lunar Soil Simulant

As the Earth’s natural satellite, the moon, an ideal platform for probing outer space, has extremely rich mineral resources. Therefore, the exploration and development of lunar resources are very important. On account of the world’s space powers, which are tensely carrying out their own lunar exploration program respectively, our China lunar exploration program is being implemented to achieve three-stage exploration targets, including "Orbiting","Landing", and "Returning"."Landing", which we are implementing as the core of second target right now, is the premise of all lunar surface activities. The footpad is lunar lander’s key part that ralates to landing safety and the implementation of follow-up work. So it is of great importance to research the interaction between lander’s footpad and lunar soil.Due to the motion characteristics of landing process, the research is carried out by test, theory and numerical methods on both vertical and horizontal directions. Vertical direction:based on self-developed device to conduct1/6impact model test, we have gained valuable test results and summarized existing impact theoretical model. Moreover, with these test results these theoretical models are evaluated in detail. In view of various aspects of indoor unit experiments carried out to obtain mechanical parameters of lunar soil and contact surfaces, we successfully established3-D dynamic finite model. Comparing with model test results, it is proved that this finite model can rationally simulate the dynamic response of the model column’s axial force, acceleration and penetration depth during the period of interaction. Horizontal direction:for the study of slide model, model tests on the process of dragging footpad in lunar soil simulant are carried out with self-developed device to investigate slip characteristics which are influenced by relative densities, sliding velocities, and penetrations and turn angles. The contents in each chapter are shown as follows:1. The study status is summarized on four aspects:lunar soil, lunar soil simulant, interaction between structure and lunar soil, and lander’s buffering mechanism. In addition, research line of this master thesis is put forward to achieve the purpose of revealing interaction between the footpad and lunar soil.2. Physical and mechanical properties of both lunar soil and its simulant are investigated and compared. Owing to the study of Mohr-colomb model and Cam-clay model, constitutive model of lunar soil simulant is initially established. With triaxial test results, it is proved that this model can accurately simulate its stress-strain relations.3. Based on the self-developed equipment,1/6impact model tests are carried out to get footpad’s response during impact process. Through a series of tests, we also gained the duration of impact action, and the relationships between these response peak and kinetic energy further.4. Plenty of laboratory tests are accomplished to put forward methods to measure the values and the range of material constants. The3-D dynamic finite element model with these parameters is established to simulate the process of impact against lunar soil. Comparing with test results, this finite model can rationally simulate the dynamic response.5. Since lunar footpad is the rigid body, the rigid impact theories that exists so far, are summerised and evaluated in detail combined with test results in chapter3.6. With self-developed device, model tests on the process of dragging footpad are carried out in lunar soil simulant to investigate slip characteristics. The test findings by being compared with NASA results are proved to be reliable.