Abstract: The interaction between footpad and soil is of great importance due to the strong impact produced during the brief period of the space lander touchdown which will affect the normal operation of the inner precision instrument. Based on the study of the landing process, the problem can be decomposed into two phases, vertical impact and horizontal sliding. A dynamic model of footpad and soil interaction is built through force balance and momentum theorem. Lots of vertical impact tests are conducted in the self-designed model test system. The soil density, impact velocity and impact mass are varied to investigate their influences on the penetration depth, the maximum axial force and acceleration of the footpad. It is concluded that the penetration depth and maximum axial force increase with impact energy increases, and tend to be stable. The denser soil is and the smaller impact mass is, the greater the maximum acceleration is. The test results are compared with dynamic model; it is proved that the dynamic model can reasonably reflect the dynamic characteristics of the lander during vertical impact.

Key words: space lander, vertical impact, dynamic model, model test