Mass and Cost Model for Selecting Thruster Size in Electric Propulsion Systems

A model of system mass and life-cycle costs is used to determine the optimal number of thrusters for electric propulsion systems. The model is generalized for application with most electric propulsion systems and then applied to high-power Hall thruster systems in particular. Mass and cost models were constructed for individual thruster strings using as inputs the number of active thrusters, the number of redundant thrusters, and the total system power. Mass and cost are related through the launch cost of the propulsion-system mass, which unifies the optimization to a single global parameter based on cost. Fault-tolerance and string cost are driving factors determining the optimum thruster size for a given system-power level. After considering factors such as fault-tolerance, cost uncertainty, complexity, ground-test-vacuum-facility limitations, previously demonstrated power capabilities, and possible technology limitations, the development of two thrusters to flight status is suggested: a low-power model operating at 20–50 kW per thruster to support missions up to 500 kW system power and the development of a high-power model operating at 50–100 kW per thruster to support missions up to 1 MW system power.