Moving-mass actuator system options for entry vehicles with deployable decelerators

This study assesses internal moving-mass actuator configuration options for trajectory control in the hypersonic regime of planetary entry. Trajectory control is achieved by shifting the location of the center of gravity relative to the center of pressure to modify aerodynamic trim conditions. The vehicle is modeled as a cylinder with a deployable forebody and a moving-mass actuator that can translate along a linear track. Placing the track in the rear of the vehicle can reduce the required actuator mass fraction for a specific trim lift-to-drag ratio by up to 5%. Increasing the length of the track similarly reduces required mass fraction. Vehicle packaging density and size do not significantly influence the required actuator mass; geometric properties such as length-to-diameter ratio and the diameter of the deployable impact the required actuator mass. Using these design guidelines, and actuator mass fraction of approximately 13% is required to achieve a maximum lift-to-drag ration similar to the Mars Science Laboratory.