Johann Mueller

Advantages and Applications of the RF-Ion Thrusters RIT

Radiofrequency Ion Thrusters (RIT) are under development in Germany at the University of Giessen and at Astrium (previous MBB and Dasa) since many years. The ion thrusters use Xenon as the propellant, generate the discharge by an RFfield at around 1 MHz and accelerate the ions by an electrostatic field applied to a 3-grid extraction system. A hollow cathode neutraliser is used as the electron source for the ignition of the discharge and for the neutralisation of the ion beam. The efficiency of the discharge is about 5 % less than that of the Kaufmann thrusters but the simplicity of the RF-thruster design and advantages with respect to the operational procedures make this thruster a serious competitor to the commonly used gridded ion thrusters. 1. The RIT Technology 1.1 RIT Operation Principle The RF-Ion Thruster ionises the propellant Xenon by collision of electrons, which are accelerated by an rf-field, with the Xenon atoms. The RF-field is coupled into the inner of the electrically nonconductive discharge vessel by an rf-coil. Ions from the plasma inside the discharge chamber are accelerated by an electrostatic field which is generated by different voltages applied to a threegrid system. Electrons are generated by a hollow-cathode neutraliser, which are used for the ignition of the discharge at begin of the thruster operation and for neutralisation of the ion beam during the thrusting periods.