Munoz Moya, Carlos (2015) Development of a monopropellant thruster design process. (PhD thesis), Kingston University, .

Abstract

A new hydrazine monopropellant thruster is needed to cover the new demands in the industry. Review on existing monopropellant thruster models proves to be inaccurate in recreating independently generated thruster designs. Additionally, an inspection of current design processes revealed a significant knowledge loss in thruster design competence and know-how over the last decades. Recovery of former capabilities and improvements in current methods are necessary to estimate the dimensions of new thruster designs and reduce the design iterations in the development process. The length of the thruster's catalyst bed emerges as the main driver in terms of modelling, sizing and performance. Existing design models set a minimum total length for the catalyst bed, which is divided into induction and post-induction regions. Available theoretical models are used to characterize both regions and their boundaries in detail. Design data from a total of 15 thrusters in collected, representing the largest compilation of thruster design data available in the literature, to compare the models' results against real data. Results show that current models overestimate the total length of the catalyst bed, proving that catalyst beds below the predicted minimum length requirements are possible. Theoretical analysis shows that the empirically based assumptions on the induction region employed by the design models are inaccurate. A new design process is proposed based on the theoretical correction of current design models which represents a more rigorous and robust approach than those currently in existence by providing a novel systematic evaluation of previous design processes and critical assessment of their range of application. With the new algorithm, the average length estimation is improved by 6.88% with respect current methods. The results from the new method yield shorter beds than previous models, which is in line with the previously observed overestimation trends. Shorter beds also imply an increased efficiency and reduced overall thruster weight, whilst more accurate estimations lead to shorter development cycles.

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