| The propulsion system is used to provide impetus for motion and control of spacecraft. At present, electric propulsion system has been widely applied in space fight missions and ascendant performance of electric propulsion makes it a substitution of traditional chemical propulsion system gradually. As a type of electric propulsion, arcjet has been the highlight of investigation and application because of its high thrust density, high ratio of thrust and power, preferable specific impulse, better system successiveness and reliability. In a space station or any other manned spacecraft, water is absolutely necessary. And till now water is the only available resource in other stars. Thus, if water can be used as propellant, drain water in manned spacecraft can be utilized, the propellant can be replenishment in other stars, and the propulsion system can share propellant storage device with other systems associate with water. Therefore, the application of water in arcjet has important significance to the research of deep space detection and manned spacecraft.To research on the performance of arcjet with water propellant, related problem of the application of water propellant is studied, an experimental model of arcjet is designed, working environment and a performance test system for arcjet is established. With these experimental setup argon is firstly used as propellant for system test, comprehensive performance data and their relations are also obtained. Further more, the test for water propellant is also performed, which validate the possibility of arcjet with water as propellant.In a typical working condition for water propellant with current of 8A and flow rate of 15mg/s, the average arc voltage is 80.5V, the specific impulse is 650s and the efficiency is about 55%~60%. The specific impulse and efficiency is higher than argon propellant, and is also higher than N2H4 propellant reported in documentations. The character of water arcjet is analyzed through experimental data. A diagnostic system for arcjet plume is also established, in which spectrum and Langmuir probe are both employed to obtain the excitation temperature and electron temperature. And in the spectral diagnostic the data was processed with absolute intensity method and Boltzmann diagram method respectively. The experiment result shows that the plume is in thermal non-equilibrium state and a large difference exists between the excitation temperature and electron temperature. The difference and its mechanism is analyzed through comparison of experiment data, and the influence of thermal non-equilibrium state on the measurement results is also discussed. |
