In this paper, a quaternion-based finite-time sliding mode attitude controller is designed for a spacecraft performing high-thrust orbital maneuvers, with cold gas thrusters as its actuators. The proposed controller results are compared with those of a quaternion feedback controller developed for the linearized spacecraft dynamics, in terms of settling time, steady-state error, number of thrust...

The correct approach to electron transport modeling in Hall thrusters is an open question in the field and is compounded by a lack of comparative studies on the relative influence of various proposed electron transport mechanisms in the thruster plume. Lacking an analytical model for transport, empirical coefficients are used in most models to reproduce major discharge parameters like the total...

The Helicon Double Layer Thruster, a new magnetoplasma thruster that accelerates ions to supersonic velocities using a current-free electric double layer, has been tested successfully for the first time inside a space-simulation vacuum chamber. Using a retarding field energy analyzer, the presence of a current-free double layer and the associated ion beam in argon have been confirmed for operat...

Experiments conducted on solid-state ionic membranes that convert atoms into ions that can in turn be extracted into energetic beamlets and thereby produce thrust are described. The capability of ionizing and transporting ions is shown to be both rapid (over 10 mA/cm) and efficient (of order 1 eV/ion). Although similar in appearance to cesium contact sources, solid-state ionic membrane devices ...

Miniature ion thrusters are well suited for future space missions that require high efficiency, precision thrust, and low contamination in the mN to sub-mN range. JPL’s miniature xenon Ion (MiXI) thruster has demonstrated an efficient discharge and ion extraction grid assembly using filament cathodes and the internal conduction (IC) cathode. JPL is currently preparing to incorporate a miniature...

1. Pulsed Plasma Thruster Pulsed plasma thrusters (PPTs) are expected to be used as a thruster for a small satellite. The PPT has some features superior to other kinds of electric propulsion. It has no sealing part, simple structure and high reliability, which are benefits of using a solid propellant, mainly Teflon (poly-tetrafluoroethylene: PTFE). However, performances of PPTs are generally lo...

We present a control algorithm for autonomous underwater robots with modular thruster configuration. The algorithm can handle arbitrary thruster configurations. It maintains the robot’s desired attitude while solving for translational motion. The attitude can be arbitrarily chosen from the special orthogonal group SO allowing the robot all possible orientations. The desired translational veloci...

Various methods for accurately determining ion species' current fractions using E x B probes in Hall thruster plumes are investigated. The effects of peak broadening and charge exchange on the calculated values of current fractions are quantified in order to determine the importance of accounting for them in the analysis. It is shown that both peak broadening and charge exchange have a signific...

Measurements are presented of the electric field at breakdown for perforated flat plates fabricated from carbon-carbon (CC) composite, Poco graphite, pyrolytic graphite (PG), and molybdenum. The perforated flat plates represent electrodes used in ion sources and ion thrusters and measurements are made with and without ion beamlet extraction through the perforations. A ranking of the materials i...