Rocket fuel injectors are in charge of propellant atomization and mixing processes, which determine the performance and stability of the liquid rocket engine itself. This small, yet significant components, are in charge of reducing the size and weight of the propellant droplets while mixing them in the shortest possible amount of time. The injector’s design and implementation must be suitable for performing their tasks in order to achieve maximum performance of the nozzle. Aiming to design and test a feasible rocket injector, a conceptual and physical design is presented, using cheap off-the-shelf stream jet nozzles, and its basic behaviour assessed. The numerical approach involves using computational fluid dynamics software (OpenFOAM) while the experimental approach involves lathe machining considerations. The numerical results indicate that the doublet injector design is feasible and mixture quality can be attained but still needs to be crafted and tested using a particular jet nozzle configuration.