High Specific-Impulse Electrospray Explorer Trajectory Guidance and Control Air Bearing Demonstration

Abstract

As small satellite mission concepts that require travel further from their traditional domain of low-Earth orbit are being considered, there is a growing need to develop small scale propulsion systems that can provide the necessary net impulse to enable deep-space operation. The High Specific-impulse Electrospray Explorer for Deep-Space (HiSPEED) project is an example concept considered for this paper, since it would be a small satellite that uses electrospray thrusters to navigate along a low-thrust spiral trajectory from Earth to a near-Earth asteroid. The NASA Jet Propulsion Laboratory Small Satellite Dynamics Testbed operates simulation and air bearing testing environments. This paper focuses on its planar air bearing platform used to create a nearly frictionless environment in three degrees of freedom: two translational and one rotational. The platform maneuvers using eight compressed air thrusters controlled by an onboard single board computer using position feedback from a motion capture system. This paper discusses the design, development, and testing of a closed-loop controller for this platform that enables trajectory following with position error less than four centimeters. The paper presents data from tests representative of HiSPEED spiral escape trajectories and operations in proximity to an asteroid along with implications for HiSPEED and similar concepts.