Enhancement of electrodynamic tether electron current collection using radio frequency power: numerical modeling and measurements

Tether electron current collection in the Orbital Motion Limited regime is one of the limiting factors in power and thrust generation applications of electrodynamic tethers. Injection of radio frequency power along tethers is considered in order to enhance electron current collection. As a basic assessment tool, Particle-In-Cell modeling of the tether system is performed using a 1-d cylindrical code. Comparison of test electron trajectories shows that the time periodic field distribution created by the RF excitation results in electrons being scattered off their usual OML trajectories, which under some conditions increases their probability of being collected by the tether. Analysis of simulation results reveals that large current enhancements can occur at resonance frequencies of the input reactance (where Xi , = 0), but at the expense of high RF power. Current enhancement is best measured in terms of the relative current variation per unit of RF power dissipated for every I-meter section of the tether. Optimum enhancements of about 9% per RF watt per meter were obtained by simulation at low frequencies (75 MHz). Similar enhancements were observed during experimental measurements on tether samples.