Experimental evaluation of a reed valve air intake system for microwave rocket in ground-static tests

Microwave Rocket, a next-generation space transportation system, generates thrust by utilizing millimeter-wave energy beamed from the ground. The thruster operates cyclically, alternating between thrust generation—where air is compressed and exhausted via millimeter-wave-supported detonation—and an air-refilling process. Although reed valve systems have been studied for air intake, their effect on thrust performance has not been experimentally verified. This study experimentally evaluates the propulsion characteristics of a thruster equipped with a six-stage reed valve air intake system (36 valves in total, length 500 mm, radius 28 mm) under ground testing. A Gaussian beam with a frequency of 170 GHz, an output power of 550 kW, and a pulse width of 1.2 ms was repeatedly applied at pulse detonation engine (PDE) cycle frequencies ranging from 50 to 250 Hz, and the resulting thrust impulse was measured. Results show that approximately 60% of the first-cycle impulse was sustained up to 150 Hz, beyond which the partial filling effect led to a decrease in impulse. The time-averaged thrust, defined as the product of impulse and PDE cycle frequency, reached a peak of 8.3 kN per square meter at 206 Hz due to the trade-off between impulse degradation and frequency increase. Furthermore, modifications to the reed valve design, specifically reducing stiffness and fundamental frequency, led to up to 80% impulse recovery and enhanced thrust performance at lower PDE cycle frequencies. • Thrust performance of Microwave Rocket with reed valves evaluated experimentally. • Approximately 60% of first-cycle impulse maintained in subsequent cycles. • Transient characteristics of intake clarified by varying PDE cycle frequency. • Optimal PDE frequency for maximum thrust influenced by reed valve design.