A rock the size of a building hurtling toward Earth: that's a scenario that makes you think. In the past, asteroid collisions and explosions have already occurred, such as the Chelyabinsk event in 2013, which caused numerous injuries and property damage. What to do if an asteroid over 330 feet (100 meters) in diameter is on a collision course? Conventional methods, like kinetic impact or gravitational tractors, might not be enough to deflect it in time.
That's where a new Chinese study, published in the journal
Space: Science and Technology, comes in. The researchers modeled two strategies to deflect or destroy these large asteroids. The first involves detonating a nuclear charge on the surface, creating a shallow crater. The second, more ambitious, uses a projectile to create a deep hole before detonating the atomic weapon inside, achieving an internal explosion.
To test these ideas, the scientists created a database of virtual asteroids and simulated different warning times, ranging from one year to twenty years. The results show that the deep crater method is significantly more effective. Thanks to better energy coupling, it could pulverize 330-foot (100-meter) rocks and effectively deflect those of about 0.62 miles (1 kilometer) in about two months, by giving them an impulse.
Detonating a nuclear charge inside an asteroid transfers a large portion of the explosion's energy to the rock, a phenomenon called energy coupling. The closer the explosion is to the center, the more efficient this coupling. The "pre-excavation" method first creates a shaft with a projectile, then places the atomic weapon inside. This technique maximizes the internal shockwave, pulverizing or deflecting the asteroid with far greater force than a surface explosion.
NASA's DART mission in 2022 already showed that a kinetic impact can alter the orbit of a small body, but when facing a massive and threatening asteroid, the energy transferred is insufficient. The Chinese team emphasizes that only a deep nuclear detonation can provide the necessary power in a short time frame. However, the composition of the asteroid – a rubble pile or solid rock – remains a determining parameter.
Transporting nuclear warheads into space raises safety and regulatory issues. Moreover, the fragments generated by the explosion could themselves threaten Earth. The researchers did not detail those, but they recommend using the surface method only in extreme emergencies with a very short preparation time. In all other cases, deep detonation is preferable. It requires a longer preparation, but maximizes the success rate.
While waiting for such a mission to become feasible, sky monitoring continues. Asteroids like Apophis, once considered dangerous, have been ruled out. But science progresses: this study paves the way for more credible planetary defense scenarios, combining drilling and nuclear explosion to protect our planet from major impacts.