• bipropellant thruster
• green propellants
• H2
• H2O2
• hydrogen
• hydrogen peroxide
• propulsion
• space
• water propulsion

In the past decade, the increasing emphasis on safety and environmental sustainability of in-space chemical propulsion systems has led to the exploration of greener, and potentially more effective, propellant combinations to replace hydrazines and other toxic propellants.
Among the available green propellants, water arguably stands out as the "greenest" of all, offering unparalleled availability, affordability, stability, non-toxicity, and material compatibility. These highly desirable properties have been known since NASA's early days, when the first concepts of Water Electrolysis Propulsion systems (WEP) were proposed.
However, to this day, all WEP systems share one significant limitation: the low density of propellants, namely hydrogen and oxygen, which are stored in their gaseous phase. This limitation has driven the development of propulsion systems towards maximising efficiencies, with short burn times and consequently low thrust levels. As a result, WEP systems in the 50 N to 500 N thrust range have largely been overlooked by industries, space agencies, and the scientific community.
To overcome the present limitations of WEP, an innovative H2O2/H2, 200 N bipropellant thruster has been investigated in this master's thesis. This denser combination of propellants could be directly coproduced onboard the spacecraft starting from liquid water, and has rarely been considered until today.
In the present work, the first steps towards the development of this engine are undertaken, starting from a comprehensive survey of potential ignition and cooling technologies. Their current state of the art is evaluated, identifying their unique advantages and disadvantages for use in an H2O2/H2 thruster.
The preliminary engine performance has been calculated at different equivalence ratios, hydrogen peroxide concentrations, chamber pressures and initial hydrogen temperatures by means of NASA CEAM. These results were then used to assess the autoignition capability of the thruster using Cantera, obtaining a first estimate of the ignition delays and the required characteristic chamber lengths.
Finally, a simplified regenerative cooling model has been developed, taking into account different cooling fluids and chamber geometries, which have been obtained from Rocket Propulsion Analysis (RPA). The convective heat flux and minimum achievable wall temperatures have been estimated at different chamber pressures and mixture ratios.
All the scripts have been developed in MATLAB® R2023b.