Lawrence Livermore Simulations Map Asteroid Deflection Using Targeted Nuclear Detonations

NASA’s 2022 Double Asteroid Redirection Test successfully altered a space rock's orbit by slamming a heavy spacecraft into it at high speed. While that kinetic approach works for modest targets with years of warning, researchers at Lawrence Livermore National Laboratory have now modeled the emergency alternative. Their new simulations map how a targeted nuclear detonation could vaporize an incoming asteroid when time has run out.[1][3]

The new study, published in The Planetary Science Journal in August 2026, maps exactly how a 160-meter-wide asteroid would respond to a nuclear blast. Rather than relying on the physical shockwave of an explosion, the technique uses the intense burst of X-rays generated by the device. These X-rays rapidly heat the asteroid's surface, causing the rocky material to vaporize and blow off into space.[1][5]

That sudden vaporization acts like a massive rocket engine strapped to the asteroid's side. The expanding gas pushes back against the remaining rock, imparting a sudden change in velocity. "These simulations give us a much more detailed picture of how an asteroid may respond to a nuclear mitigation attempt," said Isaiah Santistevan, the astrophysicist who led the study at LLNL.[1]

To build their three-dimensional models, the research team utilized LLNL’s Spheral simulation code, a specialized software tool designed to capture physical responses under extreme stress. They first validated their computational approach by running more than 1,500 one-dimensional simulations. The team then compared those baseline results against the laboratory's established Ares code to ensure absolute accuracy before moving to complex geometries.[1][3]

Mapping the disruption threshold

Once the baseline physics were confirmed, Santistevan and his colleagues pushed the Spheral code into three complex, three-dimensional disruption scenarios. They specifically modeled a 160-meter asteroid, which measures roughly 525 feet across. An object of this size is large enough to cause devastating regional damage if it were to strike a populated area on Earth.[1][5]

The simulations revealed that a one-megaton nuclear device could successfully disrupt the asteroid in two of the three tested scenarios. Disruption means the object is intentionally fragmented and dispersed across a wide debris field. If executed correctly, the blast ensures that no remaining piece poses a significant threat to the planet.[1]

However, the researchers discovered a counterintuitive relationship between the detonation distance and the resulting damage. In one scenario, triggering the device farther away from the asteroid's surface deposited less total energy into the rock. Despite the lower energy transfer, the distant blast produced much more widespread structural failure.[1]

Because the X-ray energy spread over a larger surface area from a distance, it triggered a broader vaporization event. "The finding does not mean a more distant detonation would always be more effective," the LLNL team noted. The optimal distance depends heavily on the asteroid's specific size, shape, and composition.[1]

The emergency planetary defense option

Planetary defense strategies generally fall into two categories: deflection and disruption. Deflection imparts a gentle nudge years in advance so the intact asteroid simply misses Earth. Disruption serves as the absolute last resort, designed to shatter the object into harmless fragments when a collision is imminent.[1][3]

A nuclear device remains the only practical tool for late-stage disruption because it can deliver vastly more energy than a conventional kinetic impactor. A spacecraft simply cannot carry enough mass to break apart a 160-meter rock. It also cannot achieve enough velocity to alter the trajectory if discovered less than 12 months before impact.[1][5]

"Being able to model damage, fracture and material motion in three dimensions is an important step toward improving our ability to evaluate planetary defense options," Santistevan said. The three-dimensional modeling is crucial because asteroids are rarely solid, uniform spheres of rock.[1]

Many near-Earth objects are not solid monoliths, but rather loosely bound rubble piles held together by weak gravity. A kinetic impactor might simply bury itself in a highly porous rubble pile without moving the overall mass. In contrast, a nuclear X-ray burst would instantly vaporize the outer layer regardless of the asteroid's internal structure, guaranteeing a propulsive push.[1]

Refining the simulation parameters

The LLNL team plans to expand their modeling to account for these complex internal structures in future runs. By simulating loosely bound rubble-pile asteroids, researchers hope to track how individual boulders behave under extreme stress. They need to ensure a blast does not accidentally split a threat into several large, equally dangerous pieces.[1]

The researchers also intend to validate their digital models against physical data to ensure the software accurately reflects reality. They plan to compare the Spheral simulation outputs with small-scale laboratory experiments. These upcoming tests will subject actual meteorite fragments to extreme high-energy-density conditions to see if the real rock behaves exactly like the simulated one.[1]

These physical tests will likely utilize LLNL’s Jupiter Laser Facility, where high-power lasers can replicate the intense X-ray heating of a nuclear detonation on a microscopic scale. Matching the code to real-world material responses ensures the simulations remain grounded in physical reality. This validation is essential before relying on the models for planetary defense.[1]

Preparing for the unknown threat

While astronomers have mapped more than 95 percent of kilometer-sized asteroids, the inventory of 160-meter objects remains dangerously incomplete. Dark asteroids that reflect very little sunlight can evade detection until they are uncomfortably close to Earth. This leaves no time for a 10-year deflection campaign.[1][3]

This persistent observational blind spot is precisely what makes the nuclear mitigation research so necessary. If a city-killing asteroid is spotted with only a few months to spare, emergency planners will need immediate, highly reliable data. They must know exactly where and how to detonate a device to safely deflect the rock and save the target zone.[1]

The LLNL simulations provide the mathematical foundation for those emergency protocols. By mapping the exact energy deposition required to shatter a 160-meter threat, the laboratory is building a robust contingency plan. If the worst-case scenario ever materializes, the response will be driven by physics rather than guesswork.[1][5]