Electric propulsion has been studied for a long time. Most of the electrically propelled vehicles that have been developed however have been ground vehicles. Recent research by NASA has promoted the development of electric aircraft. Most aircraft are currently powered by heavy gas turbine engines that require fueling. The development of electric motors to replace gas turbines would be a big step towards accomplishing more efficient aircraft propulsion. The primary objective of this research extends previous work by developing a high power density motor for aircraft propulsion. This design is novel because it does not require a dynamometer to provide the torque to drive the vehicle. Equally important for successful testing of the motor was the design and development of a spin pit interface that was used as a containment vessel during testing. The research led to a designed, fabricated, assembled, modeled, and tested motor. Voltages, currents and power outputs of the motor were measured and used to determine the motor’s efficiency. The gaps between the motor’s magnets were related to the current and power it produced, and modifications were made based on this relation. The vibrations of the motor were also studied and MATLAB codes were written and used to reduce these vibrations. Significant among the objectives was monitoring the temperatures of the motor’s stators due to their close association with the rotating parts. The windage and friction losses between the stators and the magnets provided a challenging hurdle in the research. These windage and friction losses were predicted, analyzed and measured, and modifications were made to reduce them. Finally, results were compiled, tabulated, and analyzed. Results obtained before and after the modifications were compared, and these comparisons were used to assess the necessity and effectiveness of the modifications. The efficiency of the motor was found to be 82.9% and the power density was evaluated as 33.1 W/lb based on a rotor weight of 497 lb. It was concluded that the litz wire used in the motor has high, frequency related impedances that could be reduced but not eliminated.

Hall Effect Thrusters (HETs) are a form of electric propulsion device which uses external electrical energy to produce thrust. When compared to various other electric propulsion devices, HETs are excellent candidates for future orbit transfer and interplanetary missions due to their relatively simple configuration, moderate thrust capability, higher thrust to power ratio, and lower thruster mass to power ratio. Due to the short history of HETs, the current design process of a new HET is a largely empirical and experimental science, and this has resulted in previous designs being developed in a narrow design space based on experimental data without systematic investigations of parameter correlations. In addition, current preliminary low-thrust trajectory optimizations, due to inherent difficulties in solution procedure, often assume constant or linear performances with available power in their applications of electric thrusters. The main obstacles come from the complex physics involved in HET technology and relatively small amounts of experimental data. Although physical theories and numerical simulations can provide a valuable tool for design space exploration at the inception of a new HET design and preliminary low-thrust trajectory optimization, the complex physics makes theoretical and numerical solutions difficult to obtain. Numerical implementations have been quite extensively conducted in the last two decades. An investigation of current methodologies reveals that to date, none provide a proper methodology for a new HET design at the conceptual design stage and the coupled low-thrust trajectory optimization. Thus, in the first half of this work, an efficient, robust, and self-consistent numerical method for the analysis of HETs is developed with a new approach. The key idea is to divide the analysis region into two regions in terms of electron dynamics based on physical intuition. Intensive validations are conducted for existing HETs from 1 kW to 50 kW classes. The second half of this work aims to construct a simultaneous design optimization environment though collaboration with experts in low-thrust trajectory optimization where a new HET and associated optimal low-thrust trajectory can be designed simultaneously. A demonstration for an orbit raising mission shows that the constructed simultaneous design optimization environment can be used effectively and synergistically for space missions involving HETs. It is expected that the present work will aid and ease the current expensive experimental HET design process and reduce preliminary space mission design cycles involving HETs.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 93-95. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 223-230). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 55-56). Also available online.

Thesis (Naval Engineer and M.S. in Electrical Engineering and Computer Science)--Massachusetts Institute of Technology, 2001. / Includes bibliographical references (p. 100-106). Also available online.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Fotis Papoulias. Includes bibliographical references (p. 69). Also available online.

This study investigates the design and aeropropulsive performance of a complete, hydrogen powered, shock-induced combustion ramjet (shcramjet) at a flight Mach number of 11 and altitude of 34.5 km. The design includes a Prandtl-Meyer compression inlet, cantilevered ramp fuel injectors, a shock-inducing wedge and a divergent nozzle. Numerical studies are undertaken using the WARP code that solves the three-dimensional Favre-averaged Navier-Stokes equations closed by the Wilcox k-ω turbulence model and the Jachimowski H2/air chemical kinetics model. Studies of fuel injection properties, mixing duct length, combustor wedge and nozzle geometry are completed to maximize the overall performance of the vehicle. The final shcramjet configuration generates a specific impulse of 1110 s. A comparison is undertaken with a scramjet vehicle at identical flight conditions and using many of the same components. The comparable scramjet generates a higher specific impulse of 1450 s although it is significantly larger and therefore heavier.

This study investigates the design and aeropropulsive performance of a complete, hydrogen powered, shock-induced combustion ramjet (shcramjet) at a flight Mach number of 11 and altitude of 34.5 km. The design includes a Prandtl-Meyer compression inlet, cantilevered ramp fuel injectors, a shock-inducing wedge and a divergent nozzle. Numerical studies are undertaken using the WARP code that solves the three-dimensional Favre-averaged Navier-Stokes equations closed by the Wilcox k-ω turbulence model and the Jachimowski H2/air chemical kinetics model. Studies of fuel injection properties, mixing duct length, combustor wedge and nozzle geometry are completed to maximize the overall performance of the vehicle. The final shcramjet configuration generates a specific impulse of 1110 s. A comparison is undertaken with a scramjet vehicle at identical flight conditions and using many of the same components. The comparable scramjet generates a higher specific impulse of 1450 s although it is significantly larger and therefore heavier.

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