Space‐charge‐limited current of vacuum arc thruster.

To optimize thrust performance, the expression of space‐charge‐limited current for vacuum arc thruster is derived from Poisson's equation. The commonly used ring‐type and coaxial‐type vacuum arc thrusters are simplified to the equivalent current sheet in planar geometry and cylindrical capacitor, respectively, for this calculation. Both the spatial distribution and peak magnitude of space‐charge‐limited current are given explicitly, together with their dependences on gap distance, applied voltage, charge number, and ion mass. For typical experimental parameters of the vacuum arc thruster, it is shown that the maximum current density drops significantly when the gap distance becomes large and grows when the applied voltage increases; moreover, a cathode material of lower atomic weight yields a higher current density. The expressions of total current for these two types of vacuum arc thruster are also presented. This work, to our best knowledge, is the first application of space‐charge‐limited current to the vacuum arc thruster and practically very interesting for engineering design. [ABSTRACT FROM AUTHOR]