Near-Earth asteroid impacts represent a significant and long-term potential threat to humanity. Defending against near-Earth asteroids has become an emerging focus and frontier in deep space exploration. The current status of international organizations such as the United Nations, as well as countries including the United States, Europe, and Russia, was systematically investigated in terms of management systems and technological frameworks for near-Earth asteroid defense. The current state of China’s defense system was reviewed, future development goals were discussed, and key development directions, including monitoring and early warning, on-orbit mitigation, disaster response, and routine system preparedness, were proposed, providing reference and guidance for building China’s near-Earth asteroid defense system.

Kinetic impact is regarded as the most technically feasible method for asteroid defense. Conducting an on-orbit demonstration and verification mission would not only enhance the technological maturity of kinetic-impact deflection，but also reveal the orbital deflection behavior of near-Earth asteroids，thereby providing decision-making support for future responses to real near-Earth asteroid impact threats. The orbital dynamical characteristics and structural，physical，and chemical properties of near-Earth asteroids are critical to the successful implementation of kinetic-impact missions. At the same time，such missions would provide an unprecedented opportunity to investigate the internal structure，composition，and mechanical properties of near-Earth asteroids. In addition，kinetic impact would serve as a unique “natural experiment,” offering a key case study for impact physics from the perspective of comparative planetology and thereby promoting the coordinated development of planetary science and planetary defense technologies. Focusing on China’s first asteroid defense demonstration and verification mission planned before 2030，this paper systematically reviews the frontier scientific questions in kinetic-impact asteroid defense，with the aim of providing a reference for mission design，implementation，and preliminary scientific research.

Combining the practical needs for future implementation of near-Earth object (NEO) defense, starting from the new requirements and problems faced by the measurement and control system, the differences between near-Earth object defense missions and conventional asteroid exploration missions as well as the mission requirements of their response systems analyzed, and research was conducted on the technical challenges in such aspects as orbit measurement and determination of near-Earth objects, improvement of space-ground data transmission capability, rapid ground data processing, on-orbit software reconstruction of spacecraft, and efficient command, control and collaboration among multiple departments. Finally, relevant recommendations for systematic solutions were put forward from three aspects: comprehensively enhancing the capability of the ground-based deep space TT&C network, improving the capacity of the asteroid defense mission center in a systematic manner, and establishing an efficient command and coordination mechanism through multi-department collaboration.

This study adopted image processing methods for trailed target and Gaia DR2 catalog data to determine position and brightness of near-Earth asteroid 2024 XA1. Combined with the data from Minor Planet Center（MPC），orbital calculations revealed that near-Earth asteroid 2024 XA1 impacted at 16:14:48 UT on December 3，2024，at coordinates 60.85°N，118.49°E. The absolute magnitude of near-Earth asteroid 2024 XA1 was 32.98～33.14 corresponding to a diameter of 0.76～0.82 meters with an albedo of 0.15. As a targeted observation experiment for hazardous asteroids，the methodology and data processing techniques developed in this study can be applied to planetary warning and defense missions in future.

To address the problem of spacecraft approach and close-range formation flying with an asteroid under the influence of perturbations, the gravitational forces of the Sun and the eight major planets, solar radiation pressure, and the gravity of asteroid were considered. By analyzing the effects of these perturbations, a control method for close-range formation flying was developed, utilizing the perturbations themselves. This method implemented a cyclic “uncontrolled-controlled” strategy that either leveraged or counteracted perturbative forces to achieve formation flying control under both distance and angle constraints. First, the influences of various perturbations on the formation orbit were analyzed by controlling variables. Then, the effects of key parameters on the approach orbit were analyzed. Finally, after the formation flying position was reached, perturbations were utilized to achieve close-range formation flying, and the effectiveness of the control method across the entire orbital period was validated. Simulation results demonstrate that the proposed control method effectively achieves coordinated distance–angle control of the spacecraft, while also offering practical engineering advantages such as straightforward implementation and low propellant consumption, providing reference for China’s future near-Earth asteroid defense missions.

To address ion beam deflection requirements for near-Earth asteroid defense, the plume characteristics and divergence mechanisms of ion thrusters were examined, establishing a far-field plume simulation framework based on PSuM. Taking the LIPS-300 thruster as an example, far-field ion beam plume simulations were conducted for typical defense scenarios. The evolution of atomic number density distribution, ion number density and potential distribution, ion velocity distribution, and axial momentum flux in vacuum were analyzed. Results indicate that within 35 meters of the target asteroid surface, the effective thrust experienced by the asteroid could be considered equivalent to the rated thrust at the ion thruster nozzle. Beyond this distance, the effective thrust diminished due to plume diffusion increasing with axial distance. Within 175 meters of the asteroid surface, the effective thrust generated by the ion beam could satisfy the requirement to deflect a 50-meter-class near-Earth asteroid by one Earth radius within five years. This study preliminarily verifies the engineering feasibility of ion beam deflection technology, providing reference for mission design of ion beam-based near-Earth asteroid deflection operations.

To address the challenges associated with limited orbit determination accuracy, insufficient knowledge of physical parameters, and the difficulty of accurately characterizing post-impact orbital deflection for potentially Earth-impacting asteroids, near-Earth asteroid 2024 YR4 was selected as the target object to investigate orbital deflection mechanism modeling and transfer trajectory optimization for kinetic impact and close-proximity observation missions. First, a high-precision orbital propagation model was established to evaluate the impact probabilities of 2024 YR4 on the Earth and the Moon. Second, the orbital deflection behavior induced by kinetic impact was systematically investigated. The primary factors affecting the magnitude of the velocity increment were analyzed, the geometric relationship between the velocity increment direction and the Sun-asteroid-spacecraft angle was derived, and a functional relationship between orbital deflection distance, mean anomaly, and velocity increment was constructed based on high-precision propagation results. On this basis, impact windows satisfying both effective deflection distance and Sun–asteroid–spacecraft angle constraints were identified, and the corresponding trajectory optimization for kinetic impact missions was carried out. Finally, for rendezvous and flyby observation missions, a year-by-year search of launch and encounter windows was performed, and feasible transfer trajectories under multiple gravity-assist schemes and flyby sequences were obtained. The modeling and analysis methods presented in this study provide reference for the investigation of asteroid orbital deflection mechanisms, while the proposed trajectory optimization framework offers guidance for the design of future asteroid exploration and planetary defense missions.

To address the challenges of complex asteroid geometries, low modeling efficiency, and unclear momentum transfer mechanisms during hypervelocity collisions, a voxelization modeling method accelerated by a Bounding Volume Hierarchy (BVH) structure was developed. Key momentum transfer laws under hypervelocity impact were computationally analyzed using the Smoothed Particle Hydrodynamics (SPH) method. The results demonstrated that compared to GPU-based voxelization methods, the present approach achieved an 86.8% efficiency gain in voxelization processing, with an voxel identification accuracy of 96.5% and particle mass errors below 3.5%. A strong correlation existed between impact angle and momentum transfer factor (β), peaking at β = 3.82 for a 60° impact—representing a 41.7% increase over the 30° impact case. Ejecta-induced recoil contributed 68.3% of the total momentum change imparted to the asteroid. This study confirms that the BVH-accelerated voxelization method efficiently handles concave geometries (7.3 times faster than conventional methods) and identifies 60° as the optimal impact angle for maximizing momentum transfer efficiency in rubble-pile asteroids (β > 3.5). The established technical framework is scalable to kilometer-scale celestial body deflection scenarios, providing critical tool support for optimizing multi-impactor collaborative trajectories.

Focusing on the defense against kinetic impact of the near-Earth asteroid 2024 YR4, the effect of orbital deflection under velocity increment deviation was investigated. Firstly, an orbital evolution model integrating planetary perturbations and impact errors was established. Secondly, the influence of velocity increment error on the orbital deflection effect of the asteroid was systematically analyzed by the semi-analytical method of State Transition Tensor (STT). Finally, the differences in the evolution of the major axis of the error ellipsoid after impact at different times were analyzed. The study found that the evolution of orbital uncertainty caused by initial velocity increment error was dominated by the orbital phase, and the magnitude of the velocity increment only affected the error amplitude rather than the propagation form. When impacts were implemented at different initial moments and evolved for the same duration, the difference in the size of the major axis of the error ellipsoid reached 3.7 times, indicating that the timing of the impact had a significant impact on the uncertainty of the orbital deflection effect. In addition, the analysis found that the Earth Star rendezvous event in 2028 will alter the expected deflection. This study provides reference for developing asteroid defense strategies that consider error propagation.