Characterization and improvement of a hybrid chemical rocket

The concerning project addresses a theoretical and practical analysis of an improved small hybrid rocket prototype. The main characteristics of the motor are: a fuel-oxidizer combination consisting of a hollow cylinder of PMMA and pure oxygen injected at high pressure (3-4 bar), and a pure convergent nozzle for which several values of the throat diameter were be tested. The main goal of the project was to characterize the rocket performance. In order to do so, first it was necessary to perform some physical improvements such as the inclusion of a pressure transducer for the estimation of the oxygen flow rate, as well as the redesign of the supporting structure and the amelioration of the data acquisition system for the obtaining of meaningful thrust readings. Moreover, a theoretical one-dimensional model was develop to contrast the empirical data and ensure its validity. Finally, three parametric studies were performed for which several experiments with different combinations of nozzle throat diameter, fuel cartridge length and oxygen tank pressure setting were carried out. The relevance of this project is significant given that this was the first phase of this prototype in which meaningful results were obtained. From the experimental phase, it was possible to conclude that the oper-ation of the device was highly transient and that the feeding oxygen orifice did not reach sonic conditions during operation against the expectations. Additionally, the correlation between the theoretical model and the empirical data showed an acceptable fitting, and although the lack of chamber temperature measure-ment was an inconvenient, it was possible to estimate the said parameter from the previous results. Finally, with respect to the parametric studies, it was concluded that: the low oxygen pressure ultimately caused that the reduction of the fuel cartridge length had no effect on the rocket performance; the largest nozzle (6mm throat diameter) coincided with the critical pressure ratio, and consequently, the smallest nozzle (4mm throat diameter) was clearly choked, although the increase in the rocket thrust was not very significant; the increase of the tank pressure was the most efficient way to increase the performance of the motor. Ultimately, it was concluded that a considerably higher thrust force could be achieved by performing future physical improvements to the deviceIngeniería Aeroespacia