Readers of a certain age will remember the golden era of asteroid movies, which culminated in two films with vastly different endings. Deep Impact depicted the devastating consequences of a massive rock colliding with our planet, while Armageddon—arguably the more kitschy of the two—was an uplifting tale of technical ingenuity and self-sacrifice. Now, the central premise of that film—essentially, using a nuclear explosion to destroy an asteroid—is taking center stage as our last line of defense against a potential Deep Impact scenario.
A new paper by researchers at the China Academy of Launch Vehicle Technology, published in the journal Space: Science & Technology, outlines two potential scenarios exploring how we might realistically destroy a space rock using nuclear weapons—and whether doing so would actually save us.
But before diving into the technical details of nuclear detonations, it is important to define the threat we face. As of July 2024, out of 35,269 discovered near-Earth asteroids (NEAs), we know of 10,933 that exceed 140 meters in diameter. If one of these rocks were on a collision course with Earth—a trajectory none of the currently known asteroids follow, it should be noted—it could cause continental or even global devastation, resulting in millions of deaths.
Alarmingly, asteroid defense experts consistently warn that simulations indicate a vast number of undiscovered near-Earth asteroids could easily catch us off guard. In some instances, the window between detecting an asteroid and the actual impact could be as short as a few days—far too little time to mount an effective defense. Therefore, it is best to plan everything in advance, and modeling is one of the simplest ways to do so. Given the extremely limited window between detection and impact, the only chance to save a significant portion of the planet is to strike the asteroid with maximum force—either to shatter it or to drastically alter its orbit. And the best method known to us for achieving this is a nuclear strike.
A new paper examines two potential ways to accomplish this goal. The first is the simplest and quickest: simply aim a nuclear weapon at the side of the asteroid and detonate it at the right moment to knock it off course. While this approach is rapid and potentially effective, it also has significant drawbacks. In such a quick-response scenario, selecting the ideal detonation point is impractical, and the “coupling energy”—the energy actually transferred from the explosion to the asteroid itself—may be relatively low. Furthermore, for the plan to work at all, the nuclear warhead must withstand a high-speed impact from debris and detonate with microsecond precision—both of which present major engineering challenges.
Anyone familiar with 1990s asteroid movies knows that the heroes of Armageddon were not astronauts, but oil drillers. As the plot goes, they excelled at one thing: drilling. It stands to reason that placing a nuclear bomb inside the asteroid would make the explosion more powerful (literally). Unfortunately, however, the likelihood of sending a team of oil drillers from shale gas fields to an asteroid—even with several years’ warning—is slim.
Instead, the paper proposes drawing on the experience of a recent, successful asteroid defense mission: the Double Asteroid Redirection Test (DART). In this mission, a harmless asteroid was struck by an “impactor”—essentially a giant metal rod—and intentionally nudged out of its orbit. On its own, this method might suffice to save Earth from a dangerous asteroid, provided we detect it early enough. However, on short notice, it cannot deliver enough energy transfer to make a significant difference. What it can do, however, is create a crater.
In the second scenario (a flyby mode involving pre-detonation excavation), the mission employs a conventional penetrator—such as a “1+1” tandem impactor, where two kinetic projectiles strike the same spot in succession—to first excavate a deep crater up to tens of meters in diameter. Once the crater is opened, a nuclear device is lowered into the excavated pit to trigger a detonation.
Simulations demonstrate why the second method is a game-changer. The deeper the explosion occurs within the asteroid, the more energy is transferred to displace the rock along the desired trajectory. For a one-kilometer-diameter asteroid, detonating a 3-megaton nuclear bomb in a shallow surface crater (i.e., one without the deep pre-excavation used in the first mode) altered the asteroid’s velocity by a mere 9.2 cm/s. In contrast, had the same bomb been detonated inside a 30-meter crater …resulting from a preliminary excavation, the change in velocity would have jumped to 30 cm/s or more—in other words, more than three times as much energy would have been transferred—had the detonation occurred inside a deep crater rather than on the asteroid’s surface.
Admittedly, there are some issues with the current simulations. The authors modeled the asteroids themselves as solid basalt—yet any planetary defense expert will tell you that hazardous asteroids are likely “rubble piles” composed of many loosely bound rocks, rather than a single, solid chunk of material. It remains unclear whether the simulation holds true for this far more chaotic (but probable) scenario, though someone will undoubtedly present mathematical arguments one way or the other.
Another major hurdle is the difficulty of executing the second scenario: the launch platform would need to match the asteroid’s orbit, conduct reconnaissance, plan a sequence of kinetic impacts, and deliver a nuclear charge to the exact same location—all while navigating the debris generated by the impact. Virtually every stage of this process represents a massive engineering challenge, one we have only just begun to tackle with missions like DART.
But perhaps the most critical aspect of all these precautionary measures is the detection of potentially hazardous asteroids. NASA’s NEO Surveyor mission, designed specifically to hunt for near-Earth asteroids, is scheduled to launch in September 2027. If it spots a rock heading straight for us, we had better have a plan ready—because Bruce Willis certainly isn’t coming to save us this time.
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