Research On Air-breathing Electric Propulsion For Nearspace Vehicles

Nearspace is of great value to national economic construction and national defense construction, so it has been a focus of research and development for years. As the main tool to help exploring and utilizing nearspace resources, the nearspace craft itself still have many difficulties in its development, because the special and complex nearspace environment places great demands on aspects such as the propulsion system. Considering the pressure condition of nearspace, an air-breathing electric propulsion system using surface dielectric barrier discharge(SDBD) as the plasma source is studied in this paper, especially focusing on its propulsion performance at sub-atmospheric pressures.In this paper, according to the parameter-varying experiment scheme and requirments, the sub-atmospheric pressure experimental platform is built up on the basis of vacuum chamber system in our lab, and discharge parameter measurement, emission spectrum measurement as well as thrust measurement are chosen as the main means to investigate thruster’s performace. Thrusters with different design parameters are designed and manufactured.The typical performance of an air-breathing SDBD thruster at sub-atmospheric pressure was investigated. Results of discharge parameter measurement show that the discharge mode of thruster is the streamer discharge, and the discharge is intermittent within a voltage cycle and discharge intensity in positive and negative half-cycles is asymmetric. The emission spectrum of the plasma generated in the discharge is measured and results are used to analyze the composition and the effect of operating condition on the plasma. The thrust, the power consumption and the efficiency(indentified by the thrust-to-power ratio) are measured as the typical propulsion performance parameters and results show that the thruster can provide a thrust on the order of 102-103μN and its power consumption is on the order of tens of Watt, and operating condition’s effect on these parameters is also studied.Parameter-varying experiments are performed to investigate the effect of some design parameters(i.e., the dielectric’s thickness and material, the streamwise spacing between two electrodes as well as the exposed electrode’s width and length) on thruster’s performance. Results show that both reducing the dielectric’s thickness and increasing its relative permittivity can increase thruster’s thrust under same operating condition, but the decrease in dielectric’s thickness will increase the power consumption while the efficiency is also increased. At low pressure level, thruster with smaller streamwise spacing can provide larger thrust and consume less power, leading to higher efficiency. The exposed electrode’s width is found to have no obvious influence on thruster’s thrust but increasing the width will increase the power consumption. Tht generated thrust is nearly proportional to the length of exposed electrode, and longer exposed electrode can lead to lower power consumption. In addition, circuit model is used to perform a preliminary analysis on the influence mechanism.