A simple arcjet operation model has been developed based on a steady-state, quasi-one-dimensional discharge/flow analysis. An operation point is determined from a voltage minimum criterion. Both high and low-voltage mode solutions are obtained. In the high mode, the discharge current is attached to the anode in the supersonic flow region. The voltage-current characteristic exhibits a favorable decreasing dependence. In the low mode, the energy input from Joule heating is done effectively in the subsonic flow region. Plural solutions which correspond to the respective modes can coexist.