Two-fluid nonequilibrium simulation of hydrogen arcjet thrusters

Abstract

A detailed numerical model has been developed to study the gasdynamic flow in an electrothermal arcjet thruster. This two-temperature Navier-Stokes model consistently incorporates viscosity, heat conduction, ohmic dissipation, collisional energy transfer between electrons and heavy species, ambipolar diffusion, nonequilibrium dissociation and ionization, and continuum radiation. The fluid equations are solved by MacCormack's method while an iterative procedure is used to relax an electric potential equation, from which the current distribution in the thruster is obtained. Using hydrogen propellant, solutions are achieved for a range of input parameters and the underlying physics and internal structures of these arcjet flows are revealed. In particular, a mechanism for self-sustaining anodic arc attachment is identified. Numerical solutions are compared with experimental results from the Stuttgart TT1 radiation-cooled arcjet thruster. Calculated discharge voltage is within 1-10% of experimental measurements, and predicted specific impulse is within 5-10% agreement. In addition, flow solutions are used to explain observed trends in performance as quantities such as the specific energy and mass flow rate are varied.