The high-precision gravitational reference sensor, which hosts a heavy test mass (TM) surrounded by electrodes with a relatively large gap, is crucial in all high-sensitivity drag-free sensors. Consequently, a dedicated locking mechanism is needed to securely hold the TM during the launch phase. After reaching the intended orbit, the TM is released to a free-falling state and subsequently captured by electrostatic actuation, which demands that the transferred momentum and angular momentum to the TM do not exceed ${10}^{-5}\mathrm{kgm}/\mathrm{s}$ and ${10}^{-7}{\mathrm{kgm}}^2/\mathrm{s}$, respectively. This paper introduces a three-level structural design of the locking-and-release mechanism. In order to investigate the release requirement, a pendulum system has been developed for on-ground testing. The mock-up of the TM is entirely consistent with the size and mass of TianQin TM, and the dual-sided release tips constrain the TM and then rapidly retract simultaneously, after which the transferred momentum and angular momentum are estimated from the free oscillations as $0.38\left(21\right)\times {10}^{-5}\mathrm{kgm}/\mathrm{s}$ and $0.15\left(14\right)\times {10}^{-7}{\mathrm{kgm}}^2/\mathrm{s}$ with a preload force of 0.3 N. This proposes a feasible scheme for validating the release mechanism conducting impulse testing for the TianQin project.

The surface of the coating or substrate structure has a rough topological structure over multiple scales, which significantly affects the actual contact area and adhesion strength. In order to investigate potential interferences during the test mass (TM) release process of the locking and release mechanism in TianQin space-borne gravitational wave detection project, an analytical model of the Johnson–Kendall–Roberts (JKR) adhesive contact with coating roughness between the TM and the release tip has been developed. This work presents the integration of the JKR theory with the Greenwood–Williamson rough surface contact theory to address adhesion challenges and influence of roughness in space-borne gravitational wave detection systems. The comprehensive model can be used to analyze how various factors such as surface shape, material properties, coating thickness and roughness affect adhesion. By introducing a numerical approach based on the Newton down-hill method to solve coupled equations for gap, stress, and load balance, the model achieves high-precision predictions of adhesion behavior under multi-scale roughness effects. By establishing relationships between force, contact half-width, and penetration depth, it provides a theoretical basis for optimizing the TM release process and the design of the locking and release mechanism. Future work will validate predictions via high-precision torsion pendulum experiments.

Space inertial sensors are crucial for space-based gravitational wave detection, requiring precise injection of test masses (TMs) into geodesic trajectories. However, conventional electrostatic suspension methods face challenges in capturing TMs with momentum exceeding 1×10^-5 kgm/s. This study proposes a novel approach to mitigate TM release momentum by leveraging controlled collisions between the locking and release mechanism and the TM. A multi-body collision dynamics model, developed in MATLAB/Simulink, simulates the in-orbit injection process under space conditions, integrating low-speed collision contact detection and electrostatic interactions. The improved injection scheme employs momentum attenuation through plunger-TM collisions and utilizes electrostatic forces for orientation control, effectively expanding the allowable momentum range during release. Simulation results demonstrate that the strategy reduces TM momentum to capturable levels of <5 μm/s linear velocity and <150 μrad/s angular velocity within 300 seconds, even under non-ideal initial conditions. The collision-based method enhances injection reliability by addressing adhesion risks and momentum uncertainties, offering a robust solution for future gravitational wave detection missions.

In space exploration missions, mechanisms often contain essential systems that perform critical operations, requiring ground testing of their functionality and performance prior to mission launch. The TianQin space-based gravitational wave detection mission will deploy three satellites forming an equilateral triangle, with the primary payload consisting of high-precision inertial sensors and free-floating test masses (TMs) that will be released by a grabbing, positioning and release mechanism (GPRM) at extremely low residual velocities. Therefore, it is necessary to design and verify the GPRM for the TianQin TM. This paper begins with an examination of the GPRM structure and workflow, after which it proceeds to present the results of experimental verification and testing of the device’s functions and performance. In addition, it offers a detailed account of the relevant motion parameters associated with the release process and provides a comprehensive simulation of the GPRM motion across the entire process. The status of the mechanism can be determined by the configured sensor output, which provides valuable guidance for the design of the TianQin TM locking and release mechanism.

The TianQin project aims to detect gravitational waves from space using a constellation of satellites, each carrying test masses (TMs) as inertial references. A critical subsystem is the grabbing, positioning and release mechanism (GPRM), which must release the TM with extreme precision. A key challenge is the lateral deflection of the inchworm piezoelectric actuator that drives the GPRM, which may compromise release accuracy. This study combines ground experiments, dynamic modeling, and finite element simulation to investigate the origin and characteristics of these deflections. Experimental results show significant lateral displacements during axial motion, which are attributed to force imbalances caused by inconsistent step lengths among piezoelectric legs. The dynamic model reveals that asymmetric driving forces induce rotational torque, leading to lateral deflections. Finite element simulations confirm this mechanism and accurately reproduce the three-axis motion. These findings provide critical insight into the actuator’s non-ideal behavior, supporting the optimization of the GPRM for reliable on-orbit operation and the success of the TianQin project.