• Hybrid Rocket
• Nitrous Oxide
• Two-Phase Flow
• Discharge Coefficient
• Self-Pressurized Tank

In this thesis models are proposed to estimate the dynamics of a self-pressurized tank of a hybrid rocket and to estimate the discharge coefficient of the injector of this system, through which a two-phase flow passes. The estimations of these models are compared with the experimental results of tests conducted at the Muroran Institute of Technology (Hokkaido, Japan). All the tests were cold flow tests, and the propellants used were nitrous oxide and carbon dioxide, which have very similar properties. From the comparison it emerged that it is necessary to model the dynamics of the vapor bubbles that arise inside the tank to obtain a general model, not dependent on experimental results, for the dynamics of the tank. Instead, the proposed formula for the discharge coefficient has been verified to be suitable for the use in cases where the flow, at injector upstream, is close to saturation conditions, while its validity for cases where the flow is supercharged must be verified with a new series of tests. Finally, models for the study of the flow through the feed line are also presented, which will have to be compared with experimental results in future works.