A charge-conservation framework for correcting secondary species emission errors in electrospray thruster ground tests

Abstract

Secondary species emission (SSE) driven by plume impingement on downstream surfaces is a dominant facility interaction in electrospray thruster ground testing and can bias intercepted-current telemetry used for in situ lifetime evaluation. Here, a charge-conservation formalism is used to develop the Electrospray SSE Control-volume Analysis for Resolving Ground Operation of Thrusters (ESCARGOT) model, which infers primary, line-of-sight plume interception currents by correcting measured electrode currents for SSE-driven transport. The model combines an analytical electrode-network formulation with numerically computed geometric factors and experimentally measured SSE yields. Application to single-emitter electrospray measurements demonstrates that neglecting SSE can substantially misrepresent both the magnitude and, in some cases, the sign of upstream electrode currents. In our example application, accelerator measurements exhibit a 64%–201% bias relative to the inferred primary current, while extractor measurements exhibit a −150% to −167% bias with a corresponding sign inversion. By improving the interpretation of intercepted-current telemetry, the ESCARGOT model strengthens the reliability of electrospray ground testing data, advancing the readiness of electrospray propulsion technology for future space missions.