Nuking Asteroids May Be The Only Way To Stop Them On Short Notice

For the Biggest Threats, Conventional Methods Fall Short, Study Concludes

When a roughly 150-meter-wide space rock called 2024 MK flew past Earth in June 2024, the warning time was only 13 days. That’s less time than it takes to plan most vacations, and nowhere near enough to mount any serious planetary defense. Now a new analysis from researchers in China argues that if humanity ever faces a large asteroid on a collision course with Earth, a nuclear detonation may be the most effective option when the threat is big and the clock is short, and in the most extreme cases, the only feasible one.

Published in the journal Space: Science & Technology, the study compares two nuclear-based strategies for deflecting or destroying large asteroids, specifically those at least 100 meters wide. At that size, a direct hit could wipe out a major city or trigger a global catastrophe. Existing non-nuclear methods, such as nudging an asteroid with a spacecraft or slowly tugging it off course over years, simply don’t pack enough punch when the rock is large and time is short, the researchers argue.

Scientists have floated the nuclear idea for decades. New here is a specific approach the authors propose and stress-test, one they say is both more effective and less technically demanding than the direct rendezvous impact method that has drawn the most attention so far.

Two Plans For Stopping Giant Asteroids

Two distinct defense strategies emerged from the researchers’ analysis. First is the direct rendezvous impact mode, a crash-and-blast approach in which a spacecraft carrying a nuclear device slams into the asteroid at high speed without slowing down, forming a shallow crater on impact before the device goes off. Its big advantage is speed: it can be launched almost immediately and needs only a relatively simple spacecraft. For a scenario where astronomers spot a dangerous asteroid with only days or weeks to spare, it may be the only realistic choice.

Serious drawbacks come with it, though. Hitting an asteroid at speeds above 10 kilometers per second makes it extremely hard to drill deep into the rock before detonating. A blast that goes off near the surface loses much of its energy to space rather than pushing the asteroid. Mission planners can’t carefully pick the impact spot in advance, and the nuclear device has to fire with split-second precision, on the order of microseconds, while surviving a punishing high-speed collision. Researchers call the engineering demands formidable and note that full-scale testing of such a system is not practical.

A second strategy, the one the researchers say shows more promise when time allows, works like a carefully choreographed two-punch combination. Called the flyby pre-excavation detonation mode, it sends a spacecraft into orbit alongside the asteroid. A conventional explosive device first strikes the asteroid at a chosen spot, carving out a deep crater. A nuclear device then autonomously navigates into that crater and detonates from inside the rock. Because the explosion goes off deeper underground, far more of its energy transfers into the asteroid instead of dissipating into space.

Depth Key To Nuclear Planetary Defense

Effectiveness hinges on how deep the blast goes, and the gap between a shallow surface blast and a deep underground one turns out to be enormous. Researchers ran computer simulations of nuclear detonations at different depths inside a kilometer-scale asteroid. Buried just 10 meters deep and detonated with the equivalent of 3 million tons of TNT, the blast produced a velocity change of about 11 centimeters per second. At 20 meters, that jumped to about 18 centimeters per second. At 30 meters, it reached roughly 30 centimeters per second. That might not sound like much, but in orbital mechanics, even a tiny nudge applied years ahead of a predicted impact can grow into a miss by hundreds of thousands of miles.

By comparison, the same 3-million-ton detonation in the crash-and-blast approach produced a maximum velocity change of about 9.2 centimeters per second for a kilometer-wide asteroid. Pushing past 30 centimeters per second, the pre-excavation approach did several times better under the same explosive conditions.

Smaller rocks are easier still. For an asteroid in the 50-meter range, a 300-kiloton blast, a fraction of the larger yield, could destroy it outright. A 100-meter asteroid hit with that same 300-kiloton detonation would receive a velocity kick of between 2 and 10 meters per second, and a 3-million-ton blast would break a 100-meter asteroid apart entirely.

Warning Time Is The Real Enemy

Much of the paper’s analysis wrestles with a grim practical question: how much advance notice humanity would actually need to pull off either approach. To model different warning-time scenarios, the researchers built a database of simulated threatening asteroids, drawing on statistics about how fast and from what directions near-Earth asteroids typically approach.

Their numbers show just how much early detection matters. A detonation that pushed an asteroid’s velocity by only 0.5 centimeters per second would still need more than four years of lead time to deflect even the most manageable simulated asteroids. A velocity change of 3 centimeters per second, roughly what the crash-and-blast method could manage under favorable conditions, cut the minimum required warning to about 560 days, though harder orbits still needed years more.

A more powerful pre-excavation blast, capable of 18 centimeters per second or more, could in theory work with as little as 139 days of warning for some asteroids, though the toughest cases still needed close to a year.

Rocket choice mattered too. For emergencies demanding an immediate launch, solid-fuel rockets, which can sit on standby and fire quickly, are the practical pick, though they carry less payload. Pre-excavation needs more equipment, so it calls for heavy-lift rockets with massive payload capacity, and those vehicles take weeks to prepare before launch. Vehicles like SpaceX’s Super Heavy Starship and China’s CZ-9 rocket, both with liftoff masses above 2,500 tons, fall into that heavy-lift class.

Getting Serious About Nuclear Planetary Defense

Neither approach is trouble-free, and the researchers say so plainly. Pre-excavation is a more involved mission with more moving parts, and it depends on having enough warning time to execute a careful rendezvous. Crash-and-blast is simpler but weaker, and it places extraordinary demands on the design of the nuclear device. Both remain conceptual, tested only in simulation, since no country has ever attempted nuclear asteroid deflection in any operational sense.

Still, the paper’s core point is hard to brush aside. For the most dangerous asteroids, the ones big enough to devastate whole continents or cause damage on a global scale, conventional methods fall short when time runs low. That near-miss in 2024, with just 13 days of warning, involved a rock too small to end civilization, but a bigger one could be, and 13 days is not enough time to do much of anything with today’s technology. A reference for the engineering design of defenses against large near-Earth asteroids is what the authors offer, a modest but real step toward turning these concepts into something operational.