Performance computation of a low-power hydrogen arcjet

A numerical analysis of a low-power hydrogen arcjet has been conducted by t aking account of the chemical and thermal nonequilibria by separating the e lectron temperature from the heavy species temperature. A sheath model is i ntroduced to the electrode boundaries to evaluate the electrode potential d rops in a coupled manner with the flow calculation. Comparison of calculate d performance far the IRS ARTUS-4 thruster with experimental results shows good agreement regarding the discharge voltage and specific impulses, altho ugh the heat loss is somewhat underestimated, To account for these discrepa ncies, the radiative loss is computed in detail, taking account of the boun d-bound, free-bound, and free-free electronic transitions in the hydrogen p lasma. The estimated radiation is found to become significant as the electr on temperature exceeds approximately 12,000 K. Contribution of the radiativ e heat transfer to the total heat loss is discussed briefly, The results su ggest that the radiation analysis may be necessary for further accurate pre diction of thruster performance, even under low-power operation.