This article proposes a reaction wheel design for angular momentum control of CubeSats using flexible printed circuit board (FPCB) windings and Halbach magnet array. Reaction wheels must provide sufficient adjustable angular momentum under the weight and space restrictions in aerospace applications. The proposed wheel is based on a three-phase permanent magnet synchronous motor with several features to minimize the weight. It consists of a coreless stator with FPCB windings and an outer rotor with a Halbach magnet array to maximize and smoothen the output torque. Different from the conventional reaction wheels with only a single-layer outer rotor, this design features a dual-layer rotor composed of inner and outer yokes. Therefore, the magnetic force acting on the bearing due to the interaction between the stator yokes and the magnets can be eliminated. Besides, instead of the conventional dual-layer rotor with magnets attached to both yokes, the proposed design only has the magnets attached to the outer yoke. According to the finite-element analysis (FEA), the proposed dual-layer rotor shows better torque ripple reduction. The reaction wheel prototypes with conventional enameled copper winding and proposed FPCB windings are both fabricated for experimental comparison. According to the experimental results, the proposed reaction wheel using FPCB windings achieves comparable performance to a conventional reaction wheel with enameled copper windings. More importantly, the weight of the proposal is lighter, and the potting process for windings can be removed to increase the overall reliability.