Exit-plane electrostatic probe measurements of a low-power arcjet

Abstract

Improved understanding of the flow processes in a 1-kW hydrazine constricted arcjet is achieved with multiple electrostatic probe surveys in the exit-plane region of the plume. Quadruple, triple, and single electrostatic probe techniques are utilized for measurements of the electron temperature Te9 density ne, and ratio of ion axial velocity to most probable thermal speed n,/cm,H+. Centerline axial profiles of Te and nc are presented for 2.2-6.2 mm downstream of the exit-plane, yielding Te = 6600 K ± 15% and nc 3.6 x 10 12 cm3 ±60% close to the thruster exit. Quadruple probe theory is modified to account for radial gradients in Te and ne over the probe radial dimension, and is used to extract exit-plane radial Te and ne profiles. Floating probe measurements yield estimates of the radial electric-field profile at the thruster exit, implying a small amount of current and ohmic heating downstream of the exit-plane. Ak cm E e / I lb 7, j k L m n