Near‑Earth asteroid impacts pose a major threat that could lead to the destruction of human civilization, having already caused catastrophic environmental changes and mass extinctions multiple times in history. In recent years, asteroids with diameters ranging from tens to hundreds of meters have frequently made close flybys of Earth, and a large number of large‑sized asteroids remain undiscovered, with warning times often only a few days to weeks. For large‑sized asteroids exceeding 100 meters in diameter, or even kilometer‑scale ones, traditional kinetic impact or long‑term force deflection methods offer limited energy and cannot achieve effective deflection within short timeframes. Using the enormous energy generated by nuclear detonation to directly destroy or rapidly deflect the asteroid's orbit is the most effective, and in extreme cases the only feasible, approach for dealing with large asteroids or those with short warning times. However, existing research on detonation defense has mostly focused on the direct rendezvous impact mode, in which the impact and detonation positions cannot be autonomously selected and energy coupling is relatively weak. Moreover, there is a lack of systematic analysis of the capability coverage and overall effectiveness of different defense modes, severely constraining the optimization of engineering designs.
In a recent study published in Space: Science & Technology , the team led by Researcher Wang Xiaowei from the China Academy of Launch Vehicle Technology proposed a novel approach to detonation defense technology for large‑sized near‑Earth asteroids. Building on the energy advantages of nuclear detonation, the study proposed two defense modes: a direct rendezvous impact detonation mode and a novel flyby pre‑excavation detonation mode. By establishing a virtual threat asteroid database and using the finite element method‑smoothed particle hydrodynamics adaptive method to simulate damage effects under various yields and burial depths, the study systematically analyzed the influence of key factors, including launch vehicle characteristic energy (C3), impact velocity, and velocity increment provided by the space transfer platform, on defense coverage and deflection effectiveness. The results demonstrate that the flyby pre-excavation detonation mode, due to its ability to autonomously select the cratering location and achieve deep detonation, offers stronger energy coupling. It can directly destroy hundred-meter-scale asteroids and achieve velocity increments of tens of centimeters per second or more for kilometer‑scale asteroids, several times higher than those of the direct rendezvous mode, while also entailing lower technical difficulty, making it the preferred option when warning time permits. When the velocity increment reaches 1 m/s, the deflection target can be achieved in only 60 days. This study provides an important theoretical foundation for mission planning and engineering design of defense against large-sized or short-warning-time near-Earth asteroids, and holds profound strategic significance for enhancing humanity's capability to respond to asteroid impact threats.
The study focuses on the severity of impact threats posed by large-sized near-Earth asteroids and the necessity of detonation defense technology, and proposes two detonation defense modes. Asteroids with diameters exceeding 100 meters can trigger large‑scale, intercontinental, or even global catastrophes, yet a large number of such asteroids remain undiscovered, with warning times often being extremely short (for example, 2024 MK had only 13 days). Nuclear detonation, due to its enormous energy, is the most effective means of dealing with large asteroids with short warning times. On this basis, the study proposes two defense modes: Mode 1 is the direct rendezvous impact detonation mode, in which a defender directly impacts the asteroid's surface at high speed to form a shallow crater, after which a nuclear device detonates within that shallow crater. Mode 2 is a novel flyby pre-excavation detonation mode, in which a space transfer platform first releases a conventional penetration device to pre-excavate a deep crater on the asteroid, and then guides a nuclear device into the deep crater for detonation. The core difference between the two modes is that Mode 1 has a simple system and can be launched immediately, but the impact location is random, energy coupling is weak, and requirements for the nuclear device's impact resistance and detonation timing are extremely stringent. Mode 2 has a more complex system and requires a longer warning time, but it can autonomously select the cratering location, achieve deep nuclear detonation, and provides strong energy coupling. To comprehensively evaluate defense capability, the study established a virtual threat asteroid database (as shown in Fig. 1), taking relative velocity (10 km/s) and angular ranges α (0°-360°) and β (40°-90°) as variables, and generated virtual asteroid orbit libraries for 1‑year and 20‑year warning times through backward integration of orbital dynamics, providing a baseline for subsequent effectiveness analysis.
The study also conducted quantitative analyses of the key influencing factors for both modes. For Mode 1, a two-pulse optimal transfer orbit model was established to analyze the effects of launch vehicle characteristic energy (C3) and maximum impact velocity on deflection time. As shown in Fig. 2, when C3 is 30 km²/s² and the maximum impact velocity is 10 km/s, only 30% of asteroids can achieve a deflection time exceeding 50 days. When the velocity is increased to 20 km/s, all asteroids have deflection times exceeding 30 days, with approximately 16% exceeding 150 days. Further increasing the velocity to 30 km/s yields only marginal gains, indicating that 20 km/s represents a more favorable design point for Mode 1, though this velocity poses significant challenges for the design of nuclear devices resistant to high-speed impact. For Mode 2, a three-pulse transfer orbit model was established to analyze the influence of the velocity increment provided by the space transfer platform on asteroid defense coverage. Fig. 3 shows that the velocity increment requirements for all virtual asteroids are below 10 km/s, with about 45% requiring less than 6 km/s. Therefore, space transfer platforms using chemical propulsion (specific impulse 300-460 seconds) or electric propulsion (specific impulse 4,000-10,000 seconds) can achieve coverage for most threat sources. In addition, the finite element method-smoothed particle hydrodynamics method was used to simulate damage effects under various explosive yields and burial depths. Fig. 4 illustrates the damage morphology of a kilometer-scale asteroid under a 3-megaton TNT equivalent detonation at a burial depth of 5 meters, showing that craters on the order of hundreds of meters can be formed and significant velocity increments can be generated.
Finally, the study compared the defense effectiveness of the two modes against large-sized asteroids and provided recommended solutions. For hundred-meter-scale asteroids, both modes can directly destroy them. For kilometer-scale asteroids, Mode 1, under a 3‑megaton TNT equivalent detonation at a shallow crater depth of 5 meters, produces a velocity increment of 8 to 9.2 cm/s. In contrast, Mode 2, with a deep crater detonation at 20 meters, achieves a velocity increment exceeding 30 cm/s, representing an order of magnitude improvement in effectiveness. Based on the virtual database, the study further analyzed the minimum warning time required for successful deflection under different velocity increments (as shown in Figs. 5 to 8). When the velocity increment is 0.5 cm/s, a minimum of 4.45 years is required; at 3 cm/s, 560 days are needed; at 18 cm/s, 139 days suffice; and at 1 m/s, only 60 days are required. This indicates that Mode 2, due to its ability to generate higher velocity increments, can substantially shorten the required warning time. In a comprehensive comparison, Mode 1 is suitable for emergency defense under extremely short warning times, though it entails high technical difficulty. Mode 2, when warning time permits, offers lower technical complexity and more reliable defense effectiveness, and can therefore serve as the preferred solution for large-sized near-Earth asteroid defense. This study provides a systematic theoretical foundation and data support for the engineering design and mission planning of future asteroid defense missions in China.