Effect of Unsteadiness and Nozzle Asymmetry on Thrust of a Microthruster

Abstract

Due to the small size and short propulsion pulses of solid propellant microthrusters, unsteady characteristics and/or fabrication errors may cause appreciable effects on the total thrust. The present work simulates a 2D planar and conical nozzle of 200 µm throat diameter using the traditional momentum equations and turbulence closure model. Unsteady characteristics were found to be insensitive to the inlet mass flux but sensitive to the chamber size. The characteristic time of transient momentum variations in the nozzle was found to be on the order of 0.1 ms, and that for decay was smaller than that for development by about 25%. This work confirmed that the magnitude of thrust was not sensitive to distortions in the nozzle geometry. A mismatch of the nozzle throat changed the position of sonic plane, but its effect on thrust was almost negligible.