Multibody Dynamics Driving GNC and System Design in Tethered Nets for Active Debris Removal

Debris removal in Earth orbits is an urgent issue to be faced for space exploitation durability. Among different techniques, tethered-nets present appealing benefits and some open points to fix. Former and latter are discussed in the paper, supported by the exploitation of a multibody dynamics tool. Critical phases as impact and wrapping are analysed to address the tethered-stack controllability: it is shown how the role of contact modelling is fundamental to describe the coupled dynamics: it is demonstrated how friction between the net and a tumbling target allows reducing its angular motion, stabilizing the system and allowing safer towing operations. The critical modes prevention by means of a closed-loop control synthesis is also shown and the connection between flexible dynamics and capture system design is highlighted, giving engineering answers to most challenging open points to lead to a ready to flight solution. Finally, an overview is given on the microgravity test campaign that has been performed to validate the multibody dynamics models.