This report aims to produce an efficient, accurate, and reliable STP thruster prototype to validate the use of an STP thruster in the Green SWaP RCS system. The Green SWaP mission goal is the development of an in-orbit capability in converting H2O into H2O2 and H2, which are used as propellants. The report first gathers the required information through a literature study, using this information to produce a series of concepts, and choosing one concept to be evaluated further. Implementing both ideal rocket theory and the thermodynamic heat equations to develop the prototype design. Verifying the prototype against the requirements set by the Green SWaP project, using numerical results to increase the certainty in the verifications made. Implementing both a steady state and transient thermal simulation with Ansys Mechanical, evaluating the system's thermal characteristics before the introduction of the propellant. An implementation of a ray-tracing simulation with Ansys Speos, evaluating the luminosity gradient seen across different cavity geometries. Evaluating the thermal and fluid properties of the system with propellant flow using Ansys Fluent, implementing a steady state simulation of the whole prototype, and a simplified 2D simulation of the nozzle, evaluating both the steady state and transient properties. The verified prototype has a nominal thrust value of 0.851827 [N], about a 14.8% reduction from the requirement due to the decrease in the effective throat and exit area caused by wall boundary conditions and a partial flow separation at the nozzle wall. Producing a specific impulse of 644.77 [s], significantly above the requirement of 500-600 [s], depending on the purity of the Hydrogen. ... Read more