Abstract: A novel ramjet based on solid-liquid phase change fuels is proposed. The fuels are solid before operation or during storage conditions and are driven from solid to liquid at operation state through microwave radiation. It improves some of the disadvantages of liquid ramjet. The principle of solid-liquid phase change ramjet is described, the concept of solid-liquid phase change fuels is established, and the index of this kind of ramjet evaluation system is put forward. The design technology of this kind of ramjet, the drive technology of phase change, the characteristics of phase change fuels,and the possible fields of application are described and analyzed. A double lower inlet ramjet based on solid-liquid phase change fuels has been demonstrated at ground tests. The phase change fuels mainly based on straight chain alkane can be stored safely with lower cost, are not afraid of glass transition, and are more suitable to be stored and used in extremely low temperature environments.

Key words: solid-liquid phase change fuels, ramjet, microwave drive phase change, low cost fuels, straight chain alkane