This paper presents an approach for the design and analysis of an attitude control system dedicated to a 3U nanosatellite using a low-cost, safe, and reliable processor-in-the-loop system for the rapid prototyping of the final product. It mainly concerns the selection between the two standard configurations of the four reaction wheels, namely the pyramid and tetrahedron configurations. The analysis was carried out by considering the presence of the mechanical uncertainties of the reaction wheels, estimated at 20% of the torque generated, and the environmental disturbances such as magnetic and gravity disturbances, solar pressure, and aerodynamic forces. It also investigates how the regulation is affected by placing the reaction wheels at or outside the spacecraft’s center of gravity. From the results obtained, it turns out that the satellite can be regulated very well regardless of the location of the reaction wheels in the satellite. When placing the actuators outside the center of gravity, a greater effort is required from the reaction wheels to change the satellite attitude, which will consume more electrical energy and wear out the wheels quickly. The torque allocation is used to distribute the forces on the four reaction wheels by means of an optimization adapted to each configuration. The analysis of degraded operation when one or two wheels fail is also studied in detail for the two mechanical configurations discussed.