Safe and clean propulsion systems for small-scale rocket launchers

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Access to space is evolving quickly, partly driven by a surge in demand for small satellites (smallsats). These are often launched ride-sharing with bigger payloads on large rockets, imposing limitations in terms of orbit and schedule flexibility. This is an opportunity for a paradigm shift in rocket propulsion systems, towards small launchers powered by safe, clean-burning and renewable propellants. The research program proposed focuses on hypergolic hybrid propulsion, an engine design that can drastically decrease launcher complexity. Hybrid rocket engines have simple construction as one of the propellants, typically the fuel, is stored as a solid in what becomes the combustion chamber, halving pumping needs compared to liquid-fueled alternatives. Our work considers hypergolic propellants, meaning that the fuel ignites spontaneously on contact with the oxidizer, removing the need for an ignition system. This hypergolic hybrid approach has the potential to bring key advantages associated with complex liquid-fueled engines to simple small-scale launchers: high specific impulse, high thrust and the ability to control thrust or re-ignite following partial burns. Current small-scale propulsion approaches providing these characteristics often rely on hydrazines and nitrogen-rich oxidizers. These propellants are extremely toxic and form polluting nitrogen oxides upon combustion. The long-term objective of enabling hypergolic hybrid rocket propulsion therefore has the potential to reduce the environmental footprint of the space industry and of terrestrial high-thrust propulsion systems (sounding rockets, pyrotechnics, etc.). The objectives addressed in the proposed work will increase the fundamental understanding of three critical reactive fluid mechanics problems hindering the development of environmentally friendly hybrid propulsion. First, we will investigate novel bio-sourced fuel matrices that have the potential to be carbon neutral, starting with sorbitol and thermoplastic biopolymers. Second, we will carry out experiments on hypergolic ignition using high-test hydrogen peroxide (HTP, 90% H2O2) as a non-toxic and nitrogen-free oxidizer. For these first two objectives, we will obtain combustion properties through simulation and experiments in our unique research facility allowing hypergolic combustion to be observed in conditions representative of hybrid rocket engines. The third objective pertains to the erosion induced by HTP reactive atmospheres on carbon-based materials, playing a critical role in hybrid engines combustion chamber structures and nozzles. The results of this work will contribute to the emergence of a clean, safe and affordable space industry for the smallsat market, an ideal opportunity to give Canada its own domestic launch capabilities. Moreover, the resulting training environment will enable 11 HQP (3 PhD, 3 MSc and 5 undergraduate interns) to acquire the skills needed to enter high-impact careers in the aerospace sector.