How do you stop a large, dangerous asteroid heading toward Earth? A new Chinese study on this topic suggests that “detonation before the start of an asteroid mission” could be the answer, provided there is enough advance warning time.
There may be millions of asteroids in our Solar System, with only a tiny fraction representing any possible, very minor threat to our planet. NASA and many other organizations scan the skies and keep discovering new asteroids, but so far, they have not identified any immediate dangers. Apophis, once considered a slight risk during its flyby of Earth in 2068, has now been ruled out as a potential issue for the foreseeable future.
Nevertheless, Earth has faced impacts from space rocks before, and even the 2013 Chelyabinsk event—a moderately sized object—reportedly caused property damage near the blast site in Russia. And, as researchers note in the new paper, asteroids measuring tens of meters or more have been tracked by Earth as they flew safely, yet closely, past our planet.
If we assume a theoretical space rock is on a collision course, with a size exceeding roughly 100 meters, simply destroying it (or even pushing it aside) may not be a practical option, the researchers stated in their peer-reviewed study published in the journal Space: Science and Technology.
“Traditional kinetic impact methods or long-term force deflection approaches have limited energy and cannot achieve effective deflection in a short timeframe,” the researchers said, adding that they found only a few comprehensive analyses on how to accomplish this. (For instance, NASA successfully altered the orbit of an asteroid moonlet using its DART spacecraft in 2022, but that was a unique space testing case.)
Therefore, a research team led by Xiaowei Wang from the China Academy of Launch Vehicle Technology has proposed instead using one of two “defense modes” for large approaching asteroids.
The first method is a simpler impact detonation: in simple terms, striking the asteroid’s surface to create a shallow crater, where a nuclear device then explodes. The other method is “pre-detonation,” or using a penetrator to create a deeper crater before detonating a nuclear warhead to “achieve deep detonation” inside the asteroid.
The simulations conducted by the researchers involved the launch vehicle’s energy, the spacecraft’s impact velocity, and the resulting changes in the asteroid’s speed under each of these two modes. Both modes were also tested on a “virtual asteroid threat database,” assuming warning times ranging from one to 20 years.
Overall, given sufficient time, the deep-crater method appears more effective. “The flyby pre-detonation mode, due to its ability to autonomously select the crater formation site and carry out deep detonation, provides a stronger energy coupling,” the researchers wrote in a press release.
Such an impact could “destroy” asteroids roughly 100 meters or so in size, as well as push away asteroids around 1 km in size, altering their velocity by roughly 1 m/s over about 60 days.
Although a shallow-crater mission could be launched more quickly, the researchers added: “The impact site is chosen randomly, the energy coupling is weak, and the requirements for the nuclear device’s impact resistance and detonation timing are extremely stringent.”
In real space missions, other factors must also be considered: the asteroid’s composition (since a rubble pile would likely require a different approach than solid rock), whether the trajectories of debris from the impact pose a threat, and how to safely deliver a nuclear warhead into space, along with many other technical issues. The researchers did not address these aspects in the press release.
However, they did propose “recommended solutions” regarding when to use each of the two options. A shallow impact might be preferable “for emergency defense” on a huge asteroid if the warning time is extremely short, since such a mission is less complex. Otherwise, a “deep impact” would be the more favorable choice.
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