High-Fidelity Multibody and Steady-State CFD Co-Simulation of Spring-Driven Separation Dynamics for Plate-Type Orbital Replacement Units

Orbital replacement units (ORUs) require precise ground-based testing of separation dynamics under simulated microgravity. A coupled multibody and computational fluid dynamics model is presented to evaluate the ground-based microgravity separation of a plate-type ORU. The satellite is modeled as a rigid, planar body, with steady-state aerodynamic loads computed at each step to provide accurate drag forces in short simulations. A payload of 1000 mm × 1000 mm × 120 mm connected to a spring ejection interface is analyzed under 500 N and 5000 N impulses with a installation offset of 0.20 m. Simulations show that without air drag, the payload maintains constant speed and overruns the table, while ambient drag quickly reduces kinetic energy, limits travel distance, and suppresses yaw motion. The results emphasize the importance of including aerodynamic damping in ground validation and demonstrate that steady-state CFD co-simulation provides reliable force prediction at a manageable cost.