A pulse-detonation thruster can generate a high-repeatability small impulse at a high operating frequency. To operate a pulse-detonation cycle in a vacuum environment without a purging material, a liquid-purge method proposed by Matsuoka et al. ("Development of a Liquid-Purge Method for High-Frequency Operation of Pulse Detonation Combustor," Combustion Science and Technology, Vol. 187, No. 5, 2015, pp. 747-764) and throat at the exit of the combustor were introduced. In the demonstration experiment, gaseous ethylene-liquid nitrous oxide, as detonable mixture, and a throat having an inner diameter of 3.6 mm (blockage ratio = 87%) were used. The measured cyclic flame-propagation speeds were 2005 ± 90 m/s and 92 ± 4% of the estimated Chapman-Jouguet detonation speed. Consequently, a 50 Hz pulse-detonation operation without a purging material in the ambientpressure range of 0.035-1.5 kPa was confirmed. A quasi-steady model, in which gases in the combustor are in the stationary state, was newly developed to investigate the operating characteristic of the pulse-detonation thruster. The experimental pressure history in the combustor during the burned-gas blowdown process was in good agreement with that of the model. Moreover, using the model, the thrust performance of the pulse-detonation thruster with a converging-diverging nozzle was investigated. It was found that the estimated specific impulse was comparable with that of the theoretical steady-state rocket engine.
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