A standardized On-Orbit Replaceable Unit with integrated mechatronic–thermal interface: Design, separation dynamics modeling, and experimental validation

With the growing demand for modular and serviceable spacecraft architectures, on-orbit replaceable units (ORUs) have become essential for hosted-payload integration. However, existing ORU interfaces remain constrained by limited adaptability across diverse host platforms, uncertain separation dynamics under manufacturing tolerances, and unresolved thermal coupling between the host and hosted satellites. To address these challenges, this paper presents a standardized ORU with an integrated mechatronic–thermal architecture, in which the mechanical, electrical-information, and thermal-control subsystems are jointly designed within a compact envelope to achieve a highly compatible, plug-and-play interface. A Newton–Euler separation dynamics model is established for the main-satellite/sub-satellite system, incorporating eccentric spring loading, gravity-gradient torque, and Gaussian disturbance modeling. Similarity-based relations are derived to interpret air-bearing ground-test data, and the measured separation velocities are compared with the model-predicted momentum partition to assess first-order translational consistency. Numerical simulations and ground experiments are then used for subsystem-level verification. Numerical simulations and ground experiments are conducted for different subsystem-level verification purposes. The thermal-control performance is evaluated using Thermal Desktop numerical simulations, the electrical-interface reliability is verified through ground electrical-continuity and communication tests, and the mechanical–separation performance is assessed through air-bearing experiments. Monte Carlo uncertainty analysis reveals that post-separation translational responses remain robust, whereas rotational responses are highly sensitive to center-of-mass offsets and spring mechanical asymmetries—providing direct guidance for tolerance allocation. Thermal Desktop simulations indicate isolation efficiencies exceeding 96% under the assumed 100 W heating conditions. Ground electrical-interface tests confirm zero packet loss across all 24 channels at baud rates up to 500,000, and air-bearing separation experiments demonstrate repeatable laboratory separation over three speed conditions, with average sub-satellite separation velocities of 0.171–0.567 m/s and average Z-axis tip-off angular velocities of 2.273–2.330 deg/s. The proposed ORU provides a prototype-level, ground-tested interface concept for standardized on-orbit servicing applications. The uncertainty-oriented modeling and verification framework established herein offers a basis for further engineering qualification, including drag/friction correction for air-bearing experiments, and future vacuum or six-degree-of-freedom microgravity validation.