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A reaction wheel is a device that consists of an electric motor and a high-inertia rotor, which when spun by the motor acts as an angular momentum storage. Reaction Wheels are utilized in the Attitude Determination and Control System (ADCS) of many spacecrafts as a means of providing the spacecraft with 3-axis attitude control. With a torque of 0.5 Nmm and an angular momentum storage capacity of 4 Nmms at 4000 rpm, the KU Leuven Reaction Wheel can easily cope with the attitude control demands of small spacecrafts, such as CubeSats up to the size of 3U. In order to deal with the excessive vibrations and unpredictable sudden rotational speed drops problem experienced by it at higher rpm, the KU Leuven reaction Wheel was partially redesigned, replacing its deep groove radial ball bearings with angular contact ones and subsequently preloading them by means of a spring washer, aiming for a maximum rotational speed of 10000 rpm, and thus a significant increase of its angular momentum storage capacity. At first, a rough sketch of the redesigned Reaction Wheel was drafted, serving as the basis for the rest of the redesign process. Next, the SKF Bearing Selection Process (with slight adaptations where necessary) was employed for the selection of a suitable bearing, as well as the determination of the various parameters, such as the desired range of preload to be applied to the system, required for its mechanical implementation. Τhis allowed for a compatible spring washer to be chosen and its minimum and maximum allowable compression to be calculated. These values were then used as inputs to a tolerance stack-up analysis, leading to the finalization of the Reaction Wheel's dimensions, which paired with the accommodation of a Hasberg foil shim within the confines of its housing ensure that the preload applied to the bearings remains within its desired range. Finally, the redesign of the KU Leuven Reaction Wheel was concluded with the production of the necessary assembly drawing and a full set of component drawings for its parts. Having completed the redesign process of the KU Leuven Reaction Wheel, an attempt to evaluate its performance was made. This involved the theoretical calculation of the electric motor's output torque and frictional moments of the redesigned KU Leuven Reaction Wheel's bearings and Oldham coupler, for the full range of possible reaction wheel operating temperatures (-10 to 40 °C). The results of these calculations, based on which a series of torque vs speed graphs was produced, suggest that the redesigned KU Leuven Reaction Wheel is more than capable of achieving the predetermined 10000 rpm rotational speed goal. Nevertheless, full validation of its design is not possible without first manufacturing a prototype and conducting a series of tests with it.