Contact Modeling and Experimental Validation of a Test Mass caging Mechanism for Space Gravitational-Wave Detection

To address the difficulty of simultaneously achieving highly reliable test-mass restraint and minimizing the risk of local surface damage during the launch phase of space-based gravitational-wave detection missions, a push-rod caging mechanism employing a combined rigid-end–compliant-end loading scheme is proposed. First, a multi-point constrained force-transmission model is established to characterize the distribution of caging forces. A conformal contact mechanics model for convex–concave spherical surfaces is then developed based on Winkler elastic foundation theory to elucidate the intrinsic relationships among contact stiffness, indentation, and caging load. Furthermore, a comprehensive static caging evaluation function is formulated to enable multi-objective optimization of the single-point caging force and spherical-tip radius. Prototype vibration tests show that, at the optimized single-point caging force of 300 N, the measured first natural frequency reaches 184.33 Hz, substantially exceeding the design requirement of 50 Hz. The mechanism withstands severe random-vibration testing without resonance-induced failure and exhibits highly coordinated multi-point load responses. Its caging capability is further validated by applying a 1500 N caging load to one side of the mechanism. The proposed mechanism and parameter-optimization method maintain high overall stiffness against external disturbances while minimizing the risk of surface damage to the test mass, providing an important reference for the design of caging mechanisms in spaceborne inertial sensors.