Reel mechanism design for active debris removal

This thesis treats the design of an innovative reel mechanism to pursue active space debris removal task. Indeed, a mechanism required to perform these task has never been developed: space reel mechanisms related to tethered missions usually were characterized by the deployment mode only; in civil fields many mechanisms are already existent but the requirements they have to fulfill are far less demanding than the requirements an ADR mission re- quires. The mechanism involved in this work is the core element of a more complex system which is composed by a net, which has the role to capture a target satellite (Envisat) and a tether which connects the net to the chaser satellite through the anchoring with the mechanism we are dealing with. The design process starts from requirements definition; then several conceptual design solutions which meet the requirements are highlighted in order to find out a baseline design which is the best solution in the author’s opinion. In particular, A reel driven by a 150W electric motor controls tether dynam- ics (to control chaser-target dynamics) in terms of deployment and retrieval rate, while an electrodynamic brake has to keep the tether length constant. A level-wind has the role to support the winding process in order to wind the tether as neat as possible. Furthermore, the most innovative device is a grip pulley; it is driven by an electric motor and its role is to keep the tether with a minimum level of tension in order to prevent tether jam inside the mechanism; to do that the pulley grabs the tether exploiting its flanges which bend one toward the other under the action of two pinch rollers. The sizing process of the different devices the reel mechanism is composed by is presented and deeply discussed; then the functioning principle is cleared and it is analyzed both in nominal and non-nominal mission scenarios exploiting a power budget. Finally, a guideline for the reel mechanism future develop- ments is presented and positive aspects, as well as negative fallouts, of the presented mechanism are discussed.