We have been developing a small rocket without combustion process designed for safe, cost-effective and eco-friendly propulsion system. We refer to the engine system of rocket as CEES (Cryogenic, Economical, Ecological, Safe) engine. The engine is a kind of cold gas engine which uses cryogenic liquid nitrogen and heated water as propellants. It is intended that pressure increase in the mixing chamber gets closer to that of a combustion engine system in such a way to take effectually advantage of evaporation of liquid nitrogen. From both simple analysis and experiments, it is found that the thrust can be approximately 540 N and is amply sufficient to fly a rocket. On the basis of the result of the thrust experiments we designed and developed a small rocket equipped with the CEES engine. On 20~th March 2005 we launched the rocket successfully. It reached a height of approximately 60 m. The flight path is almost consistent with the analytical result derived from the thrust experiments. The small rocket using engine system without combustion, which is able to take up payloads, was first launched in the world as far as we know.
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