Attitude and Angular Momentum Control for Starlab

Abstract

Attitude Control and Momentum Management are inherently coupled in the context of a space station that relies on Momentum Exchange Devices (MEDs) for attitude control. By exploiting environmental torques, attitude deviation can be minimized while limiting the saturation of the MEDs. Existing studies often simplify the aerodynamic torque contribution or omit it from controller design. In this work, a linear mean aerodynamic torque model was identified for a Right Ascension of the Ascending Node (RAAN) corresponding to the maximum aerodynamic torque magnitude, using a least-squares approach. An H∞ controller was designed for disturbance rejection for different space station configurations, where flexible-body effects were considered by reducing controller authority at high frequencies. The main findings of this work indicate that the nominal configuration of the space station lacks gravity gradient control authority for aerodynamic torque compensation, resulting in an increased attitude/momentum trade-off. The control approach was validated for a more asymmetric configuration through time-domain simulations using the derived linear model – perturbed with a representative disturbance profile constructed from data reflecting the station geometry and orbital environment – and a high-fidelity simulator. These simulations showed that the controller achieves stable performance, small attitude deviations and bounded MED momentum. Additionally, simulations were performed by varying the RAANs around the design point to identify the controller's validity region.