Abstract: In the wide application of electric thrusters, most of them accelerate positive ions to generate thrust, and need to install the neutralizer which can emit electrons to neutralize the positive ions. Otherwise it will cause the spacecraft self-charging, and the communication equipment and electronic devices will be damaged. Therefore, the neutralizer performance becomes  an important factor restricting the working state of the electric thrusters. In order to overcome the shortcoming, a kind of RF ion thruster without a neutralizer based on accelerating positive and negative ions alternately was introduced. The structural components and the propulsion principles were described. The generation of ion-ions and accelerating process of positive and negative ions were discussed. The key techniques including electronegative gas discharge characteristics and magnetic field filter the electrons efficiency, as well as the applied bias voltage way for grids in which the positive and negative ions could be accelerated alternately and periodically were pointed. The analysis results indicate this thruster has potential application prospect in the low orbit spacecraft and deep space probes.

Key words: electric propulsion, negative ion, RF ion thruster（RIT）, electronegative gas, ion-ion thruster, magnetic filter, alternating voltage