Chinese Researchers Propose Nukes as Backup Amid Warning of 15,000 Hidden 'City-Killer' Asteroids

Chinese scientists have proposed using nuclear explosives as a last-resort defence against potentially catastrophic asteroids after new research suggested thousands of undetected 'city-killer' space rocks could threaten Earth.

The study, conducted by researchers from the China Academy of Launch Vehicle Technology in Beijing and reported this week, argues that a nuclear device buried deep inside an incoming asteroid could be the most practical option in scenarios where existing planetary defence methods cannot respond in time.

However, it's worth noting that the proposal is based on computer simulations and has not been tested in real-world conditions.

For years, scientists have become increasingly concerned about smaller near-Earth asteroids that are difficult to detect but still capable of causing widespread destruction if they strike populated areas. NASA scientists have warned that as many as 15,000 asteroids measuring several hundred feet across may remain undiscovered.

Because some of these objects could be detected only days or weeks before a possible impact, researchers are exploring emergency response options that go beyond existing asteroid deflection missions.

Hidden Asteroids Could Leave Little Time for Defence

According to the study, conventional planetary defence strategies may be ineffective if a hazardous asteroid is discovered shortly before it reaches Earth.

One example is NASA's Double Asteroid Redirection Test, or DART, which successfully altered the orbit of the asteroid Dimorphos in 2022 by deliberately crashing a spacecraft into it.

While DART demonstrated that asteroid trajectories can be changed, that approach depends on identifying a threat well in advance. Researchers argue that shorter warning times would make it difficult to launch and complete a similar mission before impact.

To examine an alternative, the Chinese team modelled a scenario in which a spacecraft drills deep into an incoming asteroid before placing a nuclear device inside the cavity. Rather than detonating the weapon on the surface, the researchers found that an underground explosion would transfer far more energy into the rock, increasing the chances of destroying or significantly altering its course.

The researchers wrote that the study 'can provide references for the engineering design of defense against large near-Earth asteroids.'

Nuclear Asteroid Plan Relies on Early Detection

The team tested different asteroid sizes, speeds and flight paths using computer simulations. According to results published online, a 164-foot asteroid could be destroyed using a 300-kiloton nuclear explosion, roughly equivalent to 20 Hiroshima bombs. A much larger object measuring nearly 1,000 metres would require a 3-megaton explosion under the same modelling.

The depth of the detonation also proved significant. Researchers found that placing the nuclear device around 100 metres below the asteroid's surface tripled the change in its velocity compared with a shallower explosion, suggesting that drilling would be a key part of any future mission.

Even so, the concept faces major practical challenges. Any mission would require enough warning to identify the asteroid, launch a spacecraft, reach the target and successfully drill into its surface before a collision became unavoidable. It would also depend on developing spacecraft capable of transporting both specialised drilling equipment and a nuclear payload through deep space.

Despite those obstacles, the researchers said the work 'holds profound strategic significance for enhancing humanity's capability to respond to asteroid impact threats'.

The proposal is not the first time nuclear technology has been considered as a planetary defence measure. Last autumn, scientists also discussed whether a nuclear option might be necessary for asteroid 2024 YR4 after it briefly raised concerns over a possible Earth impact on 23 December 2032.

Those fears have since eased. NASA's Center for Near Earth Objects has reduced the probability of 2024 YR4 striking Earth to just 0.00081%. However, the likelihood of the asteroid hitting the Moon on that date has increased to more than 4%, according to the report.

Researchers noted that a lunar impact could still have consequences. Debris created by such a collision could threaten satellites and spacecraft orbiting Earth, while material falling back onto the Moon could complicate future robotic missions and pose risks for astronauts involved in the Artemis programme.

Although the latest study presents nuclear detonation as a possible emergency response, its findings are based entirely on simulations. No decision has been made to pursue such a strategy, and any future use of nuclear devices for planetary defence would require technological advances, international cooperation and confirmation that the approach is both safe and effective.