Performance additives for hybrid rockets

Abstract

Addition of performance-improving materials in the solid hydrocarbon fuels of hybrid rockets has been studied extensively both in academia and also in the industry. The primary motivation has been to improve the specific impulse, density impulse, and regression rate performance of the propulsion system. Despite the fact that hybrid rockets are particularly suitable for the inclusion of performance additives, which are typically in solid phase, successful implementation has been quite difficult to achieve. In this paper, we evaluate the feasibility of using performance additives with the following primary objectives: (a) develop a comprehensive survey of fuel additives (and the best binders) for hybrid rockets in order to establish the state of the art in the field, (b) rank these additives based on performance and a number of important practical factors, and (c) recommend a subset of promising additives for further evaluation. Even though, this feasibility study primarily makes use of the information in the open literature, new thermochemical calculations has also been conducted in order to establish the theoretical performance of various propellant systems operating at a common reference state (i.e., chamber pressure, nozzle expansion ratio, etc.).