This AFO proposal is for a parabolic flight campaign that is critical to Technology Readiness Level (TRL) 6 advancement of current TRL 4 reaction sphere prototypes. The technology is similar to single-axis reaction wheels, but can advantageously provide attitude control in all three degrees of rotational freedom for Size, Weight, and Power (SWaP) savings. Reaction spheres will improve the pointing accuracy and stability for small satellite (smallsat) missions requiring long duration imaging and tracking, and for missions experiencing large disturbance torque accumulations. Along with ongoing development efforts, the proposed free-flying experiments in zero-gravity are needed to adequately validate the technology. This proposal leverages a strong partnership between NASA Goddard Space Flight Center and the Northrop Grumman Corporation (NGC). The NASA/NGC collaboration has been ongoing for over a year and is enthusiastically supported by management in both organizations. NASA/NGC have successfully iterated through several sphere designs and the current status of technology maturation is extremely favorable since basic feasibility, at a minimum, has been demonstrated for the three primary technology challenges, which are: (1) designing the control scheme and systems architecture; (2) designing a low-friction method of containment; (3) characterizing the reaction sphere system in simulated environments. The primary objectives in the proposal are to use the zero-gravity environment for validating two versions of reaction sphere prototypes and to obtain performance data (e.g. torque, pointing accuracy, pointing stability) in a relevant environment. The free-flying payload is a 1U CubeSat adaptation equipped with onboard accelerometers and other sensors. Additional equipment are mounted directly to the flight vehicle. Four pre-programmed attitude maneuvers will be executed during the zero-g parabolas and used to assess the performance of the sphere prototypes. Each maneuver will be repeated at least three times. Data collected from zero-g experiments will be used to down-select from the two sphere prototypes and to calculate fiction losses needed for further optimization. The ultimate vision for this technology initiative is the widespread integration of reaction spheres on smallsats and to enable new classes of science opportunities requiring precision attitude control and prolonged science campaigns.