Chinese rocket scientists have modelled the most effective way to nuke a doomsday asteroid, and it is not a blast at the surface: first drill a hole, then bury the bomb about thirty metres down, which their simulations say more than triples the deflection

If an asteroid large enough to end a city, or worse, were ever found on a collision course with too little time to nudge it gently aside, the option of last resort has always been the crude one: hit it with a nuclear bomb. A team of Chinese researchers has now worked out, in detail, how to do that far more effectively, and the answer is not the version from the films.

The important caveat comes first. This is a simulation study, a piece of modelling on a computer. No such device exists, nothing has been built, and nothing has flown.

I am a writer with a long interest in this beat, not a physicist, so treat this as a careful reading of the work rather than expert testimony.

The two-step method

The study, led by Xiaowei Wang at the China Academy of Launch Vehicle Technology in Beijing and published in the journal Space: Science and Technology, compared different ways of using a nuclear device against a threatening asteroid.

The approach it favours comes in two steps. First, a metal penetrator slams into the asteroid and digs a deep hole. Then a second spacecraft drops a nuclear bomb into that hole, so it detonates buried well beneath the surface rather than against it. As Space.com reported, the simulations found that a 3-megaton explosion, roughly 200 times the Hiroshima bomb, could blast apart an asteroid around 100 metres across.

The headline number is about depth. Placing the bomb about 30 metres down, rather than setting it off at the surface, more than tripled the change in the asteroid’s speed in the model. That is a large difference for the same weapon, and it is the whole point of the paper.

Why burying it matters so much

The physics behind that is intuitive once you picture it. A bomb detonated at or above the surface throws most of its energy uselessly out into space, and only a fraction pushes on the rock. A bomb buried inside couples far more of its energy into the asteroid itself, either shoving it harder or breaking it apart, depending on what you are trying to do.

As the South China Morning Post noted, the two-step design is also less demanding than the obvious alternative of driving an intact bomb into an asteroid at enormous speed. Separating the digging from the delivery lets engineers choose where the charge goes and how deep, instead of relying on a violent impact at a random spot.

When you would actually reach for a nuke

It is worth being clear about where this sits, because a nuclear option is not the first choice and is not meant to be.

The gentler and better-understood method is kinetic deflection, simply crashing an ordinary spacecraft into an asteroid to shift its path. NASA demonstrated it with DART in 2022, and China itself has a kinetic-impact test mission planned for later this decade. But a kinetic nudge is tiny. It only works if you catch the asteroid years or decades early and let that small shove accumulate.

The nuclear case is the one where that comfort has run out: a large object found with little warning, too big and too close for a gentle push to save you. In that corner, a nuclear device is one of the few things that could deliver enough energy quickly enough to matter. This study is really about making that grim, last-ditch scenario more survivable, not about a routine tool.

The caveats that matter

Several things need saying plainly, because a headline about nuking asteroids invites overreaction in both directions.

The first is that this remains a model. Simulations are how this kind of work has to begin, since no one is going to test a real nuclear device on a real asteroid, but a result in a computer is not the same as a proven capability.

The second is that blowing an asteroid apart is genuinely contested among scientists. Fragmenting a rock risks turning one large threat into several smaller ones, and whether the pieces disperse harmlessly or some still strike Earth depends on details that are hard to model with confidence. Careful deflection, moving the object intact, is generally seen as safer than disruption where there is any choice.

The third is legal. The Outer Space Treaty, which almost every spacefaring nation has signed, prohibits placing nuclear weapons in orbit around the Earth or on celestial bodies. Whether a one-off interception of an incoming asteroid would fall foul of that is itself an unsettled question, and it is not one a simulation can answer.

What to watch

The realistic near-term work in planetary defence is still the unglamorous kind: finding and tracking the objects that could threaten us, and flight-testing the gentle kinetic methods that only work with early warning. Nuclear options, Chinese or American, remain on the drawing board, studied precisely so that the knowledge exists if it is ever truly needed.

That is probably the right place for them to stay. The value of a paper like this is not that anyone is about to launch a bomb into deep space. It is that if the worst ever came, someone would already have thought carefully about how to aim it.