Eddy-Current Actuator for Attraction and Repulsion of Non-Ferromagnetic, Conductive Spacecraft

Abstract

This paper introduces a propellant-free approach to mobility of an inspection or servicing vehicle. The approach is suitable for motion near the surface of non-ferromagnetic, conductive objects in orbit. This work considers the specifics of eddy-current interactions between a translating permanent magnet and the aluminum surfaces of spacecraft. Such an actuator moves within the body of an inspection vehicle, requiring that its motion remains limited if the vehicle is to continuously interact with the client spacecraft. Experimental verification on a low-friction air track verifies a model for attraction–repulsion dynamics at millimeter-scale initial separations in one dimension. Results show good agreement between the simulated and tested conditions and motivate extension of the model to more general cases. To bound the design space and relative distances at which this actuator is effective, this work identifies the required size, mass, and trajectories for repulsion that restores the actuator to its initial configuration. Results support the utility of eddy-current actuation for microsatellites at separations of millimeters to centimeters from their conductive clients. For such clients the actuator may enable relative mobility and achieve other objectives key to proximity operations.