Microwave-driven plasma for miniature space propulsion*

Microwave-driven Coaxial Transmission Line Resonator (μ<!--[if gte msEquation 12]> style='font-size:11.0pt;line-height:107%;font-family:"Cambria Math",serif;
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KO;mso-bidi-language:AR-SA'>μ-CTLR) produces a small-volume high-density plasma plume. When operated at low pressure, the γ discharge mode (characterized by increased electron temperature, electron density, and gas temperature) was attained even at low power levels [1]. These characteristics of the μ<!--[if gte msEquation 12]> lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Cambria Math",serif;
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KO;mso-bidi-language:AR-SA'>μ-CTLR show promise for low-power micro-propulsion systems. In this study, we investigated the propulsion capability of the μ<!--[if gte msEquation 12]> lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Cambria Math",serif;
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KO;mso-bidi-language:AR-SA'>μ-CTLR operating at 900 MHz and 8W power, with argon gas. At the gas flow rate of approximately 100 SCCM, the measured plasma parameters are electron density of 1×10²⁰ m^-3, electron temperature of 3.5 eV, and gas temperature of 4000 K in the middle of the plasma plume. These results suggest a minimum thrust of 1.5 mN with a power consumption of only 8 W. The corresponding thrust-power ratio (TPR) is about 190 mN/kW and specific impulse (Isp) about 51 sec. These performance metrics are comparable to or even surpass recent micro-propulsion systems [2].

[1] Kim K, Nam W, Lee S, Lee J, Shim S, & Yun G. S. (2022), Plasma Sources Science and Technology, 31(10), 105006.

[2] Tsifakis D, Charles C, & Boswell R. (2020), Frontiers in Physics, 8, 34.