The Research On Testing Technology Of Electric Thruster Ground Experiment System

The electric propulsion technology is an advanced space propulsion technology. Its specific impulse is several times higher than that of the conventional chemical fuel engine, greatly improving the payload of satellites and extending the orbit life of satellites. Its thrust is typically less than1N, but the electric thruster has many firing times and a long working time, obtaining a great total impulse still after the time accumulation. Helicon wave plasma thruster (HPT) has a high ionization efficiency and a great specific impulse, suitable for the space propulsion of lager quality satellites and probes. Microcavity discharge thruster (MCDT) has a tiny size and thrust, suitable for the space propulsion of nano-satellites.The electric thruster ground experiment is an important part of electric thrusters’ development, providing the effective data support for the electric thruster working performance verification. This paper firstly conducts a detailed engineering design for helicon wave plasma source as the core component of HPT. The structure size of the discharge tube and copper coil is designed. The distribution of magnetic field strength inside the discharge tube is simulated with different load current and center distance between coils. The length of helicon antenna is17cm when the magnetic field intensity peak is0.02T. The overall structure diagram of helicon wave plasma source is drawn. Thrust is among the important performance parameters for the electric thruster, and then the research on small thrust measurement method for the electric thruster is carried out. The thrust produced by the electric thruster can be split into continuous pattern and pulse pattern. Continuous thrust may be regarded as constant force. The measuring physical quantities of pulse thrust include single pulse, flat pushing force of muli-pulse and total impulse. The kinetic equation of common low thrust measurement devices is analyzed. When the input quantities are constant force and pulse force respectively, the output quantities are the gantry dynamic response of different forms. Different methods of small thrust measurement are required by means of the function relationship between the input quantity and the output quantity. Plume is an important basis reflecting the working performance of the electric thruster. The methods of langmuir probe diagnosing plume plasma parameters divide into three ways:single probe method, double probe method and triple probe method. Through the analysis of volt-ampere characteristic curve between probe volt and probe current, the method to calculate the plasma electron temperature and electron density can be obtained.According to the working characteristics of the electric thruster, the testing system of the electric thruster ground experiment based on virtual instrument is designed. The DAQ, scanning power supply and sensors meeting the testing requirement are chose. LabVIEW is used to develop the software platform. The software graphical user interface is simple and intuitive, convenient to operate. And the switching between different interfaces is smooth. The testing system can achieve measurement, display storage and query of the parameters such as small thrust, working fluid’s flow, vacuum degree and wall temperature of discharge chamber. Volt-ampere characteristic curve of the probe is displayed, and electron temperature and electron density of plume plasma can be calculated directly.The software testing platform is debugged and has a good function performance. And it is successfully applied to the microcavity discharge jet device experiment. And the optimal combination of parameters such as working fluid’s flow and pressure, out diameter and electrode spacing is determined regarding jet length as measurement index.