The interface defeat and dwell can effectively improve the ballistic performance of ceramic armors under high velocity impact of long rod projectiles. Confinement conditions along both axial and radial directions of ceramic armors can affect these behaviors. With the aim of giving an insight into the effect of cover plate thickness and connection mode of cover plates with confining tubes on these behaviors, numerical simulations were performed in which the confined silicon carbide (SiC) targets with cover plates were impacted by tungsten rods. The pressure on the surfaces of SiC targets with fixed cover plates are compared to that with free cover plates, showing that the plates fixed with the confining tubes can produce higher pressure by way of wedging. With the increase in cover plate thickness, the dwell duration of the tungsten rods on the ceramic interface gradually grows. In addition, the upper and lower limits of transition impact velocities for the SiC targets with cover plates in different connection modes (i.e., free or fixed) were obtained and analyzed. The results show that the increase rate of the transition velocity region for the cover plate with the fixed-mode is relatively stable and lower than with the free-mode. On this basis, the fixed cover plate contributes higher ballistic performances to the SiC target than the free cover plate. It is also noteworthy that the size of transition velocity region does not enlarge linearly with the increase in cover plate thickness due to the slow growth of the upper limit. Accordingly, thickness thresholds exist, which are 5 mm and 6 mm for the fixed and free cover plates, respectively. Considering the ballistic performance and economy, the cover plate with the thickness ranging from 3 mm to 5 mm, i.e., 1.5~2.5 times of the tungsten rod diameter, is ideal for the structural dimensions in this paper.

The DART mission has validated the feasibility of full-scale kinetic-impact asteroid deflection, but pre-mission uncertainties in target physical properties remain a critical challenge to reliable prediction of deflection effectiveness. A physics-informed machine learning method, termed Physics-Informed Kinetic-Impact Effectiveness Prediction (PI-KIEP), is developed for the asteroid 2015 XF261 kinetic-impact demonstration mission to jointly predict the momentum enhancement factor β and the target velocity increment Δv under a baseline impactor configuration. Cross-validation results show that the PI-KIEP model achieves high predictive accuracy for both β and Δv, with pooled out-of-fold R² values reaching 0.956 and 0.982, respectively. Model interpretation and impact-process analysis show that porosity and strength primarily control local momentum coupling, whereas target size governs the global velocity response through residual-target inertia. This distinction supports the joint evaluation of β and Δv and identifies porosity and size as priority parameters for pre-mission characterization. Late-stage spallation further modifies momentum enhancement according to the kinematic and separation states of the resulting fragments, highlighting the need to characterize these states in post-impact observation and mission assessment. PI-KIEP provides a physically consistent and interpretable approach to predicting deflection effectiveness and identifying key risk target-property parameters under limited-data conditions. The resulting parameter sensitivities and physical interpretations in this study can support mission design and risk assessment for the 2015 XF261 kinetic-impact mission.

Currently, space debris environment engineering models typically simplify millimeter-sized debris as homogeneous spheres, neglecting the influence of debris shape on orbital evolution and subsequent risk assessment. To improve these models, this paper proposes the use of cylindrical debris instead of spherical debris. Specifically, cylinders with varying aspect ratios are employed to represent different debris shapes, and cylinders of differing densities are spliced together to simulate non-homogeneous debris characteristics. Three representative debris shapes are selected, and their attitude dynamics under non-homogeneous conditions are modeled. Finally, this study analyzes the attitude dynamics of these three debris types in the low Earth orbit (LEO) environment and summarizes the distribution of their nutation angles. Results show that, due to aerodynamic torque, the nutation angle distribution of non-homogeneous debris is positively skewed, with the concentration value being less than 90°. Moreover, the stronger the aerodynamic torque effect, the greater the degree of skewness. In contrast, the nutation angles of homogeneous debris cluster around 90°, exhibiting a symmetrical distribution. This study provides a method for calculating the attitude distribution of space debris, making it possible to incorporate debris attitude as a factor in environment engineering models.