Stability and Performance Experiment in a Water Arcjet

Paper number

IAC-09.C4.P.18

Author

Dr. Lingyun Hou, China

Coauthor

Dr. Yan Shen, China

Coauthor

Dr. Huangzai Tang, China

Year

2009

Abstract

Water is an essential substance for the space exploration involving mankind activities. It is also known that water has been discovered on other planets such as the moon, Mercury and Mars and is abundant in the outer solar system. If water can be used as propellant, the supply will possibly be replenished from the other planets in future. All of this means that the thruster using water as a propellant has enormous potential for human spaceflight missions. However, it also faces a huge challenge in designing the arcjet thruster because of its unstabilty.
    In this study, serious unstable mechanisms of original water arcjet are analyzed. The experiment simulating the vaporization of water shows the fluctuation of plume and arc voltage mainly results from the vaporization process in the supply pipe. There are two types of fluctuations, i.e. the low-frequency with large amplitude and the high-frequency with small amplitude, which are caused by pressure drop and density wave, respectively. The low-frequency oscillations can be removed by increasing the throttle. The high-frequency oscillations result from the nature of water phase-change.
    A new supply pipe made of capillary bundles and a buffer is developed and the principle of stable vaporization in capillary bundles is presented. The mutual offset of many random fluctuations with the same period in capillary bundles can suppress the intensity of oscillations. In addition, the use of capillary bundles increases the area of vaporization in the heating section. The vaporization of water becomes faster and more complete. The experiment of vaporization shows that the integration of capillary bundles and the buffer can reduce the fluctuation of density wave effectively. The amplitude of fluctuation is controlled within 2.9\% over the average without obvious period. By use of this system, a relatively stable vaporization of water in pipes is achieved.
    The above scheme is applied in the supply system of water arcjet. Performance research is carried out in a new designed thruster using water as a propellant. From the image of plume, it is seen that water arcjet can work stably within a certain range. In the performance experiment with the flow rate form 20mg/s to 30mg/s, specific impulse approaches between 530s and 580s and the efficiency reaches from 40\% to 55\% when the power ranges from 500 to 700W. The experiment results prove that the stability of water arcjet is improved greatly and good performance is obtained.

Abstract document

IAC-09.C4.P.18.pdf

Manuscript document

IAC-09.C4.P.18.pdf (🔒 authorized access only).

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