Optimization Procedure for Electric Propulsion Engines
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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This thesis addresses the optimization of all types of space electrical propulsion thrusters. From the Langmuir-Irving payload mass fraction formulation, a dual-optimum solution is defined, yielding a minimum overall mass for a specified payload consistent with minimum transfer time. This solution fixes the ideal payload mass ratio mpl mo at a value of 0.45, establishing the ratios of effective exhaust velocity v Vc and incremental change of vehicle velocity deltau Vc to characteristic velocity at 0.820 and 0.327 respectively. The characteristic velocity Vc includes thrust time as well as engine efficiency etat and specific power alpha. A range of mass ratios from 0.35 to 0.55 is used in order to allow the system designer some flexibility while remaining close to optimal. Nine examples are presented which demonstrate that mission profiles can be optimized by profile-to-thruster matching. A comprehensive list of currently available electric propulsion engines is provided. This list details important parameters such as the specific power, which sizes an engine in terms of power provided to the thruster at the cost of additional mass. Allowance is, also made for a fuel tank mass penalty, and examples show that this can also noticeably influence the optimum design.
- Electric and Ion Propulsion