To study the effects of parameters in smoothed particle hydrodynamics (SPH) simulations of hypervelocity impacts on basalt, numerical analysis and validation were performed using the Riemann-SPH method based on ground-based impact tests. By adjusting various simulation parameters, the influence of parameters on the simulation can be obtained. Results show that both algorithmic and material parameters significantly influence the simulation, with coupling between strength and damage models. Applying the artificial stress method helps suppress tensile instability in solid impacts. Using the Wendland C² kernel with a target of 2.5 particles within the smoothing length optimizes both accuracy and efficiency, and variable-resolution particle distribution improves performance by over 20 times. In simulations, the impactor may undergo a phase transition, and different model and parameter combinations can yield similar responses. It is recommended to employ the Lundborg strength model and the Benz-Asphaug stochastic damage model, which better represent the mechanical behavior of rocky materials, and to account for phase transitions. Parameter search should be constrained by reasonably known values to avoid large errors or non-uniqueness. With reasonable parameters, simulated crater size and momentum transfer factor match experiments within 10%–20% error. These strategies support SPH applications in asteroid defense and parameter selection.

The Gravity Tractor (GT) is a spacecraft that deflects an asteroid using its gravitational force to gradually alter the asteroid’s trajectory without making physical contact. This paper proposes a comprehensive mission optimization framework to maximize orbital deflection distance in variable-mass GT missions, incorporating key constraints: launch performance, warning time, and operational strategies. Simulation results suggest that the deflection distance of GT does not increase linearly with warning time due to launch window constraints, and the three-pulse transfer scenario does not provide significantly greater deflection distance compared to the two-pulse transfer scenario. Moreover, in the static hovering scenario, the deflection distance first increases and then decreases with the effective tractor distance, whereas in the displaced orbit scenario, it decreases monotonically. Finally, considering the launch performance of CZ-5, a 10-year warning time enables the defense against 50-meter asteroids, while a 20-year warning time enables the defense against 100-meter asteroids. This research provides valuable insights into the evaluation of GT deflection efficiency and the engineering design of GT-based missions.

A graphical analysis-based search algorithm for the transfer orbit state sequence is presented to address the problem of high manual involvement when designing the transfer orbit for the Callisto orbiting mission using graphical analysis approaches. Through the analysis of graphical properties and resonance gravity assists, the variation pattern of orbit states is summarized, and an iterative search algorithm for solving the state transition sequence is proposed. The algorithm can obtain multiple transfer sequences rapidly and efficiently, as demonstrated by the simulation of the transfer orbit for the Callisto orbiting mission. The solution of the corresponding transfer orbits for the obtained sequences shows that the spacecraft can achieve the transfer from a Jovian highly elliptical orbit to the Callisto orbiting orbit within 2.13 years by consuming a velocity increment of 2.108 km/s, saving approximately 100-200 m/s of velocity increment and about 1 year of transfer time compared to other methods. The method proposed in this paper solves the problem of high manual involvement when using graphical analysis methods.