An air-breathing system using reed valves was developed for Microwave Rocket. No stopper plate was used to avoid interference between the reed valve tip and high-power microwave beams in the thruster tube. Titanium alloy was used for the reed petal because of its high strength. The petal's width and thickness were designed to be tapered to prevent the petal from yielding, and its fundamental frequency, opening area, and the maximum stress on the petal were computed using static analysis. Estimated fundamental frequency agreed well with the measurement, though the opening area and the maximum stress were underestimated because of the inertial force. The experiment was conducted using a high-power microwave generator (gyrotron) to evaluate the air-breathing performance. In the experiment, no plastic deformation was observed on the reed petal and the partial filling rate was deduced as 0.32-0.44 for two reed valve stages (16 reed valves).

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The gas-liquid equilibrium propulsion system mounted on the solar sail IKAROS is restricted to pulse ejection because of the limited capacity to separate the gas and liquid, and thus it is only applicable to attitude control. If the continuous ejection performance is improved, however, this propulsion system can be applied to various small satellites to control the orbit. Continuous ejection is realized by suppressing the cavitation that occurs when the gas is ejected. This study suggests a new system to suppress the cavitation where two types of liquefied gas that are insoluble in each other are used as propellants. This shows the feasibility of improving the performance of continuous ejection based on microgravity experiments.

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