The NSTAR ion engine model, designed for the DS1 and Dawn missions, is implemented in a gravity-tractor spacecraft to support hovering operations. The model takes under consideration the operational limits of the thruster as well as the Isp profile for varying throttling levels. A gravity-tractor system was modeled and subject to operate under different guidance laws over a variety of asteroid configurations. Our results indicate the importance of an accurate propulsion system model for the gravity-tractor by showing that under certain scenarios, the propellant efficiency of the dynamic hovering laws is improved with respect to the classical inertial hovering.
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