The thrust characteristics of a conical nozzle were experimentally determined using helium, partially ionized by a high energy electric arc, as the working fluid. The thrust produced in the supersonic section of the nozzle is presented in dimensionless form as the total thrust less the thrust produced in the convergent section. Data for divergence half angles of 20°, 25°, and 30° are presented as a function of the Reynolds number and the ratio of the exit area to the throat area for area ratios varying from unity to 250. The experimental thrust data were compared with values predicted by one dimensional nozzle theory corrected for boundary layer effects.