Semi-Active Damping System Characterization for Landing in Microgravity

The landing of space probes in microgravity poses very challenging problems both from the dynamical and technological point of view. The main problem of designing a damping system for landing in microgravity is the high uncertainty associated with the feature of the soil (i.e. damping and stiffness coefficients), therefore a highly robust design relying only on passive system is not possible. In this work a new approach to increase the robustness of the damping system for landing in microgravity is proposed, coupling a passive granular shock absorber with a semi-active piezoelectric based friction damper which can modulate the applied braking force using fast piezoelectric actuator acting on a sort of brake pad. The proposed concept has been carefully modelled, identifying characteristic parameters of both the passive and active parts. In the case of the granular shock absorber, numerical discrete elements simulations have been validated conducting an experimental campaign in relevant conditions. Then the identified model of the semi-active damping system has been used to conduct an extensive sensitivity analysis of the performance achievable in a wide range of landing velocity and soil features.