The increasing number of constellation satellites requires re-thinking of the design and manufacturing process for reaction wheel rotors. Mass optimisation of reaction wheel rotors leads to cost reduction and performance increase. Those optimisations can be realised by taking ideas from nature. Therefore, design principles of diatoms were screened, abstracted and implemented in an algorithm-based design process. In this way, a bio-inspired rotor was created, which considers launch and in-operation loads, is capable of up to 7500 RPM and shows a compact design with a diameter of 282 mm. Regarding mechanical performance, an energy density of 4661 J kg^-1 and a mass moment of inertia ratio of 0.7584, which considers the component and an idealized design, could be achieved. Compared to a commercial rotor, this is equivalent to a similar inertia ratio and +85 % energy density, but +44 % mass due to manufacturing restrictions. Based on different boundary conditions, different first natural frequency for launch and operation conditions were obtained (658 Hz and 210 Hz). The new design was cast from nano-reinforced aluminium alloy (AlSi10Mg + Al2O3) in 3D-printed sand moulds that were produced via binder-jetting process. Thus, a hybrid manufacturing process was used, by combining additive manufacturing and casting. Post-processing of the cast part via turning and milling was performed to compensate distortion and achieve the required surface quality. Preliminary vibration measurements were performed, showing a large need for balancing to achieve low vibration emissions.