Aerodynamic Characterization of Fin Configurations for VLEO Attitude Stabilization

The Very Low Earth Orbit (VLEO) regime, typically defined as altitudes below 450 km, offers several advantages for space missions, including enhanced spatial resolution, reduced communication latency, improved radiometric performance, and the possibility of payload miniaturization. From a system-level perspective, the increased atmospheric drag present in this environment also contributes to orbital sustainability by promoting natural deorbiting of spacecraft and debris. However, the same aerodynamic effects introduce persistent forces and torques that significantly impact spacecraft attitude dynamics, making conventional attitude control approaches increasingly challenging. In traditional Low Earth Orbit missions, attitude control is commonly achieved through reaction wheels, magnetic torquers, or thrusters. In VLEO, the elevated disturbance environment reduces the effectiveness of these actuators and increases the likelihood of saturation, motivating the investigation of alternative control strategies. Aerodynamic attitude control, particularly through the use of passive or semi-passive surfaces, has therefore emerged as a promising solution to exploit the surrounding atmosphere for stabilization and momentum management. Previous studies have primarily focused on fixed aerodynamic configurations, such as shuttlecock- and feather-type designs. Shuttlecock configurations generate strong restoring torques in pitch and yaw by orienting surfaces at large angles relative to the flow, providing high passive stability at the expense of significant drag and limited roll authority. Feather configurations, in contrast, align surfaces more closely with the freestream, reducing drag and enabling partial three-axis control, but typically at the cost of reduced passive damping. To address these limitations, this work introduces a hybrid aerodynamic fin configuration that combines the stabilizing properties of shuttlecock designs with the directional control capabilities of feather-like surfaces. Each fin is characterized by two geometric degrees of freedom: a tilt angle, defined as a rotation about the hinge axis at the fin root, and a twist angle, defined as a rotation about the fin spanwise axis. This hybrid arrangement enhances aerodynamic torque modulation while maintaining a fixed-geometry architecture compatible with the stringent mass and volume constraints of CubeSat platforms. The aerodynamic characterization of the proposed configurations is carried out using a panel-based numerical framework suitable for rarefied flow conditions. A dedicated MATLAB-based design and analysis pipeline is developed to automate fin geometry generation, mesh creation, aerodynamic simulation, and post-processing. Fin geometries are parametrized over a range of tilt and twist angles, and aerodynamic forces and torques are evaluated for varying spacecraft attitudes relative to the incoming flow. The resulting dataset enables a systematic assessment of control authority, damping characteristics, and torque generation capabilities across the design space. The analysis indicates that hybrid tilt–twist fin configurations can achieve a favorable balance between passive stability, control authority, and drag reduction when compared to classical shuttlecock and feather designs. These findings support the viability of hybrid aerodynamic surfaces as an effective means of attitude stabilization and control for CubeSats operating in VLEO. Future work will focus on formal stability analysis to characterize equilibrium robustness, multi-objective optimization to balance aerodynamic performance metrics, and the integration of adaptive control strategies capable of exploiting variable fin geometries in real time.