The operating characteristics and operation procedure of the closed loop experimental facility under subsonic power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. It was found that there are two ways of operation for the subsonic power generation, which are (1)a subsonic operation both under non-power and power generation and (2)a supersonic operation under non-power generation and subsonic operation under power generation. For the operation(1), Mach number at channel inlet decreases to ˜0.6, therefore it is required to generate plasma under this Mach number. On the other hand, if the plasma cannot be generated, the operation(2) needs to be carried out. In this case, a shock wave appears in the generator channel, then the influence of a large pressure change and a vibration caused by a shock wave in the generator channel needs to be considered.