In recent years Cube Satellites have become more and more popular mainly because of their simplicity and wide range of use cases. Because these satellites are so small, they need precise steering systems, called reaction control systems. In this paper a nozzle for such a system is designed. The effects of boundary layer formation on the overall efficiency were researched and the nozzle was optimised to achieve maximum efficiency, while also being precise and easy to manufacture. For that, own tools to calculate the nozzle geometry and to simulate a thrust event were programmed in python.