Design, development and testing of 3D-printed conformal energy absorbing structures

Abstract

Landing a spacecraft on a foreign body is a key challenge to explore new worlds. Besides the task of approach and decent the landing has to nullify the residual kinetic energy. For large or medium-sized landers this will be done by the landing gear with shock absorbers inside the landing legs. For small landers alternative ways of reducing the shocks of the touchdown have to be developed, since the landing gear has a higher mass fraction when the lander gets smaller. A suitable method for protecting a lander from the shock of impact is a crushable shell, which absorbs the kinetic energy at touchdown by plastic deformation of its core material. The core material is commonly made of aluminum honeycomb which is very lightweight and has a constant energy dissipation characteristic. On the other hand, the materials stiffness strongly relates to the direction of load, since tilted load transfers reduce the energy absorptivity drastically. This applies specially for landers with no active guidance and control ability. In those cases, the entire vehicle has to be covered with crushable elements with the honeycomb cells aligned accordingly. A new and innovative method of omni-directional crash protection is a metal grid which can be manufactured additively. With this feature the lander can land in any inclination without losing crush performance. In this paper the development of a 3D-printed energy absorbing structure is presented. Hardware tests have shown the effectiveness of this method in comparison to the benchmark of honeycomb shock absorbers.