Performance tests and simulations for Taiji-1 inertial sensor

Taiji-1 satellite was successfully launched on 31 August 2019, and it has been operating normally in orbit until now. A series of in-orbit experiments were carried out with the inertial sensor, which included the micro-thrust test, drag-free control test and laser interferometer test. Comprehensive performance simulations and tests of the inertial sensor were also carried out prior to the launch of Taiji-1, including the calibration and drop-tower tests. These tests were one of the preconditions for the success of these experiments. The calibration experiments were conducted in a cave-lab using the gravity-inclination method and the scale factors of the inertial sensor along Y- and Z-axis were measured. In addition, 20 drop-tower tests were carried out in the National Microgravity Laboratory of China (NMLC) drop tower and the control stability of all the axes was tested and optimized. A simulation model was used before each test, and the results showed that an accurate simulation prior to each experiment had an important role in ensuring the efficiency and accuracy of the experiment. The circuit-gain switch was realized for the first time during the drop-tower tests. The test results indicated that the microgravity level of the NMLC drop tower could reach about 13 [Formula: see text]g0 along the horizontal axes, offering an important reference for researchers planning to conduct microgravity experiments in the NMLC drop tower.

Selective Transport of Airborne Microparticles Through Micro-channels Under Microgravity

This paper analyzes the possibility of obtaining the selective transport of microparticles suspended in air in a microgravity environment through modulated channels without net displacement of air. Using numerical simulation and bifurcation analysis tools, we show the existence of intermittent particle drift under the Stokes assumption of the fluid flow. The particle transport can be selective and the direction of transport is controlled only by the kind of pumping used. The selective transport is interpreted as a deterministic ratchet effect due to spatial variations in the flow and the particle drag. This ratchet phenomenon could be applied to the selective transport of metal particles during the short duration of microgravity experiments.

The Adhesive Response of Regolith to Low-Energy Disturbances in Microgravity

Small, airless bodies are covered by a layer of regolith composed of particles ranging from μm-size dust to cm-size pebbles that evolve under conditions very different than those on Earth. Flight-based microgravity experiments investigating low-velocity collisions of cm-size projectiles into regolith have revealed that certain impact events result in a mass transfer from the target regolith onto the surface of the projectile. The key parameters that produce these events need to be characterized to understand the mechanical behavior of granular media, which is composed of the surfaces of small bodies. We carried out flight and ground-based research campaigns designed to investigate these mass transfer events. The goals of our experimental campaigns were (1) to identify projectile energy thresholds that influence mass transfer outcomes in low-energy collision events between cm-size projectiles and μm-size regolith, (2) to determine whether these mass transfer events required a microgravity environment to be observed, and (3) to determine whether the rebound portion of these collision events could be replicated in a laboratory drop tower environment. We found that (1) mass transfer events occurred for projectile rebound accelerations <7.8 m/s2 and we were unable to identify a corresponding impact velocity threshold, (2) mass transfer events require a microgravity environment, and (3) ourdrop tower experiments were able to produce mass transfer events. However, drop tower experiments do not exactly reproduce the free-particle impacts and rebound of the long-duration microgravity experiments and yielded systematically lower amounts of the overall mass transferred.