Development and Test of a foldable Protection System for a small Landing Probe using 3D-printed Metal Grids as Shock Absorber

Kurzfassung

The exploration of our solar system has progressed continuously during the past decades. Here, especially the planets stood in the foreground of investigation. But in order to study the formation of the solar system and the evolution of life within the focus has shifted now also to smaller bodies like comets, asteroids and smaller moons of the planets. All those objects have similarities with regard to their weak gravitational field and their absence of an atmosphere. Small landing probes in the range of less than 20kg therefore face the challenge of landing without the help of a parachute and possibly without a propulsion system. A suitable technique 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. Past studies revealed the effectiveness of this method, which has also been used for the landing probe Schiaparelli of the ESA Trace Gas Orbiter. But landing probes like Schiaparelli rely on an active Guidance, Navigation & Control (GNC) system to keep its right orientation, since the shell is only on the bottom side of the lander. A less complex and lightweight solution could be to cover all sides of the lander and thus to omit the GNC and propulsion system completely. The obvious challenge with this kind of design is the need for an unfolding mechanism, which would remove the crushed shell elements from the lander body in order to have a free and unobscured field of view for the instruments and antennas. Another innovative design concept is the use of a core made of 3D-printed metal grids instead of commonly used aluminum honeycombs as the primary shock absorbers. The advantage of the metal grids is the multidirectional energy absorption capability which is not given with the honeycomb. With this feature the lander can land in any inclination without losing crash performance. In this paper we present and discuss the design, manufacturing process and breadboard testing of a small landing probe encapsulated in a crushable shell made out of 3D-printed metal grids core and GFRP face sheets