Analysis of plume-lunar surface interaction and soil erosion during the Chang’E-4 landing process

Abstract When the lander approaches the lunar surface, the rocket exhaust will erode the surface and eject massive high-speed dust, which could damage the payloads on the lander or interfere with subsequent surface operations. This process also provides a unique opportunity to study the plume-dust interaction and the wind erosion on the surface of airless body such as the Moon. Previously, limited knowledge was obtained from Apollo landing images and a simplified erosion model is built to study the erosion process. With high-quality data acquired in the landing process of Chang’E-4 (CE-4) mission, for the first time, we aim to quantify the dust ejection angle and erosion depth for a low-thrust lander, test the effectiveness of the current erosion model, and provide reference information for future landing missions. We use image measurement methods to extract key parameters such as dust ejection angle and erosion depth from the landing image of CE-4. For comparison with the observation, we also employ an erosion model to estimate the erosion thickness. The dust appears at about 7 s before the lander touch the surface, with a height of 13 m above the surface. When the nozzle altitude was about 0.6 m, the dust ejection angle is measured to be above 7°, while the dust ejection angle calculated by the particle trajectory method is less than 4.3°for particle sizes smaller than 1 mm. For the first time, an average erosion depth of 0.7 cm is measured between 1.12 m and 2 m from the nozzle centerline for a low-thrust lander. The measurement corresponds to an erosion time duration from 1.1 s before landing to 0.4 s after landing. The measured erosion range using CE-4 data is much larger than the estimated erosion radius given by the previous erosion model. It indicates that the dust’s angular distribution, local topography of the landing area, and other factors are important in improving the precision of the erosion model.