When liquid nitrogen and heated water are mixed in a chamber, pressure increase due to evaporation expansion inside the chamber becomes high enough to generate thrust force for rocket propulsion. This thrust system is safer and environment-friendly compared to conventional rocket engines utilizing combustion process. This new type of rocket engine system is called "Water-Liquid Nitrogen rocket engine system" and it can be used for small payload mission with expected altitude of several kilometers. In this paper, experimentally obtained thrust characteristics are shown and analyzed. As a result, relations between the thrust force and the mixing chamber pressure are clarified. Also, it is found that the present injector can attain only half of the theoretically expected specific impulse due to insufficient mixing efficiency.
