Analysis and Experimental Determination of Fluid Dynamics Within a Sphere for the Development of Multi Degree of Freedom Attitude Control Actuator

Abstract In the contemporary landscape of spacecraft engineering, reaction wheels, control moment gyros, and momentum wheels are standard tools for precise attitude control, functioning by exchanging angular momentum through the rotation of a solid mass around its major axis. The VEKTOR-FDA (Vector Fluid Dynamic Actuator) proposed in this paper offers an alternative by utilizing the principle of rotating liquid to generate angular momentum instead of relying on a solid body. Electromagnetic pumps drive and circulate the fluid, connecting to a hollow sphere via inlet and outlet channels. The fluid within the sphere is drawn into the pump through the outlet channel and reintroduced through the inlet channel. This circulation, combined with the spherical shape, generates a rotational fluid flow inside the hollow sphere, creating a rotating fluid volume and an angular momentum vector aligned with the rotation axis. By utilizing at least three pumps arranged orthogonally, simultaneous operation allows flow mixing, which can be precisely controlled by adjusting the individual flow velocities of each pump. This setup enables the rotation axis of the fluid flow to be directed in any desired orientation, allowing the rotating fluid volume and its angular momentum vector to be spatially aligned as needed. As a result, a single VEKTOR-FDA actuator can manage attitude control across all three axes of the spacecraft, effectively functioning as a multiple-degree-of-freedom (MDOF) actuator. The electromagnetic pump drive in the VEKTOR-FDA actuator provides self-lubrication and eliminates the need for moving mechanical parts, minimizing potential damage from mechanical loads like shocks during launch. Its simple design also enables the use of commercial off-the-shelf components, ensuring cost-effective implementation. This paper provides a comprehensive overview of the motivation and concept behind the VEKTOR-FDA actuator. Additionally, this paper presents analyses and experimental results that investigate how rotating fluid flow can be generated within the sphere and examines its behavior. The study evaluates various factors influencing fluid flow inside the sphere, including configurations with variable cross-sectional shapes of the inlet and outlet channels. Furthermore, it determines the optimal positioning and arrangement of these channels to achieve efficient fluid flow volume, which is essential for maximizing angular momentum output.