Power transfer efficiency in an air-breathing radio frequency ion thruster

Due to a series of challenges such as low-orbit maintenance of satellites, the air-breathing electric propulsion has got widespread attention. Commonly, the radio frequency ion thruster is favored by low-orbit missions due to its high specific impulse and efficiency. In this paper, the power transfer efficiency of the radio frequency ion thruster with different gas compositions is studied experimentally, which is obtained by measuring the radio frequency power and current of the antenna coil with and without discharge operation. The results show that increasing the turns of antenna coils can effectively improve the radio frequency power transfer efficiency, which is due to the improvement of Q factor. In pure N_2 discharge,with the increase of radio frequency power, the radio frequency power transfer efficiency first rises rapidly and then exhibits a less steep increasing trend. The radio frequency power transfer efficiency increases with the increase of gas pressure at relatively high power, while declines rapidly at relatively low power. In N_(2)/O_(2) discharge, increasing the N_(2) content at high power can improve the radio frequency power transfer efficiency, but the opposite was observed at low power. In order to give a better understanding of these trends, an analytic solution in limit cases is utilized, and a Langmuir probe was employed to measure the electron density. It is found that the evolution of radio frequency power transfer efficiency can be well explained by the variation of plasma resistance, which is related to the electron density and the effective electron collision frequency.

Design and analysis of an underwater inductive coupling power transfer system for autonomous underwater vehicle docking applications

We develop a new kind of underwater inductive coupling power transfer(ICPT)system to evaluate wireless power transfer in autonomous underwater vehicle(AUV)docking applications.Parameters that determine the performance of the system are systematically analyzed through mathematical methods.A circuit simulation model and a finite element analysis(FEA)simulation model are developed to study the power losses of the system,including copper loss in coils,semiconductor loss in circuits,and eddy current loss in transmission media.The characteristics of the power losses can provide guidelines to improve the efficiency of ICPT systems.Calculation results and simulation results are validated by relevant experiments of the prototype system.The output power of the prototype system is up to 45 W and the efficiency is up to 0.84.The preliminary results indicate that the efficiency will increase as the transmission power is raised by increasing the input voltage.When the output power reaches 500 W,the efficiency is expected to exceed 0.94.The efficiency can be further improved by choosing proper semiconductors and coils.The analysis methods prove effective in predicting the performance of similar ICPT systems and should be useful in designing new systems.