A Theoretical Analysis of Vacuum Arc Thruster and Vacuum Arc Ion Thruster Performance

TLDR

Vacuum‑arc thrusters that generate high‑velocity plasma jets or serve as plasma sources for electrostatic acceleration have been proposed or are under development, and their regular discharge behavior permits simple semi‑empirical performance models. The authors use empirical measurements of current density, ion charge state, velocity, and cathode mass‑loss rate to derive expressions for thrust and specific impulse versus geometry, and compute electrical efficiency and thrust‑to‑power ratio from burning‑voltage data. The analysis estimates performance across many cathode materials, showing that vacuum‑arc thrusters can operate efficiently with diverse propellants, offering high flexibility in specific impulse, and that plasma‑production efficiency is largely scale‑independent, making the approach well suited for micropropulsion.

Abstract

Thrusters that exploit vacuum arc discharges to produce high-velocity plasma jets directly or as sources of plasma that is subsequently accelerated electrostatically have been proposed or are currently under development. Vacuum arc discharges exhibit certain regularities in their behavior that allow the performance of these thrusters to be described by simple semiempirical models. Empirical data on the current density distribution, charge state and velocity of ions created in vacuum arc discharges, and the total cathode mass loss rate are used to develop expressions for the expected thrust and specific impulse as a function of thruster geometry. Thruster electrical efficiency and thrust-to-power ratio are calculated based on measurements of the burning voltage for given thruster operating parameters. Estimates of achievable thruster performance for a wide range of cathode materials are presented. This analysis suggests that thrusters using vacuum arc sources can be operated efficiently with a range of propellant options that gives great flexibility in specific impulse. In addition, the efficiency of plasma production in these devices appears to be largely independent of scale because the metal vapor is ionized within tens of micrometers of the cathode electron emission sites, so this approach is well suited for micropropulsion.