The results of experimental investigation of the ST-40 Hall thruster operating with a heating hexaboride cathode are presented. The readiness of the heating hollow cathode to the thruster start was assessed by reducing the cathode keeper voltage from the start value of 100 V to 15 ... 17 V, when an internal discharge in the hollow cathode occurred. Various cyclograms of the thruster start are considered with the definition of the purpose of the cyclogram, which ensures reliable thruster start. Three cyclograms of the thruster start are investigated: with the thruster’s electromagnet coils switched on; with the coils off; without switching off the voltage at the hollow cathode keeper, which made it possible to restart the thruster without preheating the hollow cathode. The obtained cyclograms make it possible to ensure a reliable start of the ST-40 thruster when operating with a heating hexaboride hollow cathode. In the course of laboratory research, the PPU-300 power processing unit was used. It ensured the stabilization of the discharge power in the thruster’s accelerating channel and stabilization of the currents supplied to the central and external coils of the thruster. The main operating characteristics and parameters of the ST-40 thruster were obtained for three fixed values of the discharge power: 265, 281, 300 W and a change in the mass flow rate of the working substance (Xenon) through the anode unit of the thruster 0.7 ... 1.3 mg/sec. Experimental investigation of the ST-40 thruster in a wide range of parameters made it possible to determine the optimal thruster’s parameters that provide the maximum values of thrust and specific impulse for the given values of the discharge power in the accelerating channel of the thruster and the minimum discharge current. The process of the thruster’s parameters optimizing was carried out by changing the currents flowing through the internal and external coils of the thruster. In the course of experimental research, it was found that the inner coil and the serially connected outer coils can be connected in parallel and powered by a single power supply. Experimental studies have confirmed the correctness of the adopted technical solutions in the development of the ST-40 Hall thruster and the heating hexaboride hollow cathode.
Today in the world there are many electric propulsion systems based on the different types of thrusters. Most of them used gaseous propellent. Typical Electric propulsion system (EPS) consists of following main subsystems: the electric propulsion thruster that creates thrust; the power-processing and control unit which provides energy to all subsystems; the storage and feed system that performs functions of storing working substance in the tank and supplying the required amount of working substance to the thruster; Solenoid valve is a part of storage and feed systems. The feed system is an essential part of any electric propulsion system. The life cycle of the feed system is largely determined by lifetime of the valves and the amount of working substance in tank. Whereas the amount of working substance is selected based on the requirements for each specific mission valve parameters must be satisfying for various missions. Accordingly, the valves must have low power consumption, high reliability with a long lifetime (more than 106 cycles), low weight and dimensions. Solenoid valve is an electromechanical device that consists of moving part controlled by an electromagnet. Movement of the movable element and the seal are key parts of valve reliability. Presented solenoid valve design uses two membranes, which perform the function of centering the moving element and with the spring provide the required closing speed and the seal of the valve. The paper presents the problem of selecting critical elements that affect the solenoid valve's performance, procedure and test results required for the qualification of space equipment. Manufactured valve was successfully tested (vibration testing, response time testing with inlet pressure change, response time testing at different operating voltages, dependence of the valve actuation current on the operating voltage, temperature testing, lifetime tests) separately and as part of XFS according to the ECSS standards. As well as the successful implementation of presented valve into the flight xenon feed system for electric propulsion.
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