Matthias Weiand

Millimeter-wave-supported detonation (MSD) is a unique detonation phenomenon driven by a supersonically propagating ionization front, sustained by intense millimeter-wave beams. Microwave Rocket, which utilizes MSD to generate thrust from atmospheric air in a pulse detonation engine (PDE) cycle, is a promising low-cost alternative to conventional chemical propulsion systems for space transportation. However, insufficient air intake during repetitive PDE cycles has limited achievable thrust performance. To address this issue, a model equipped with a six-stage reed valve system (36 valves in total) was developed to ensure sufficient air intake, which measured 500 mm in length, 28 mm in radius, and 539 g in weight. Launch demonstration experiments were conducted using a 170 GHz, 550 kW gyrotron developed at the National Institutes for Quantum Science and Technology (QST). Continuous thrust was successfully generated by irradiating up to 50 pulses per experiment at each frequency between 75 and 150 Hz, in 25 Hz increments, corresponding duty cycles ranging from 0.09 to 0.18. A maximum thrust of 9.56 N and a momentum coupling coefficient $C_m$ of 116 N/MW were obtained. These values represent a fourfold increase compared to previous launch experiments without reed valves, thereby demonstrating the effectiveness of the reed valve configuration in enhancing thrust performance.