How Giant Magnets Could Shield Earth from Hazardous Asteroids

Scientists propose a groundbreaking method to alter the course of potentially hazardous asteroids using a giant magnet. This innovative approach, known as non-contact orbital velocity adjustment (NOVA), aims to mitigate the challenges associated with traditional kinetic impactor techniques, which involve colliding a spacecraft with an asteroid to redirect it. However, as of now, this method remains untested, leaving its effectiveness uncertain.

Günther Kletechka from the University of Alaska Fairbanks introduced the NOVA concept at the Lunar and Planetary Science Conference in Texas on March 17th. He focused on the NOVA application for the asteroid 2024 YR4, which was initially thought to be on a collision course with Earth or the Moon in 2032. Fortunately, subsequent observations indicated it would safely pass by.

This asteroid, less than 70 meters in diameter, represents a manageable target for location adjustment. The proposed spacecraft features a large, superconducting magnet that is approximately 20 meters wide, powered by a nuclear fission reactor. A small booster would maintain its orbit around the asteroid, allowing it to stay within 10 to 15 meters of the surface and interact with its iron content.

While a magnet could theoretically deflect a solid iron asteroid, most asteroids consist of smaller fragments held loosely together in what is known as a rubble pile. “It’s a pile of rubble with virtually zero tensile strength, so you can’t push the whole body effectively,” stated Kletechka during his presentation. He cautioned that kinetic impactors could fragment such asteroids, creating debris that may fall to Earth.

In contrast, the NOVA spacecraft would gradually extract pieces from the rubble pile and trap them in a magnetic field at its center. Each collected fragment would increase both the spacecraft’s mass and magnetic field strength, easing the extraction of subsequent pieces. This technique allows the spacecraft to slowly shrink and control the asteroid’s movement.

To delay the trajectory of YR4 effectively, Kletechka estimates that at least 170 days of continuous operation would be essential. Although he believes that this electromagnetic deflection strategy is feasible, he acknowledges significant uncertainties. The precise quantity of iron in 2024 YR4 remains undetermined, although educated guesses suggest it’s adequate. Furthermore, maneuvering a spacecraft so close to an asteroid for extended periods has not been attempted before and poses unique challenges.

“Including this tool in our Earth’s defense arsenal is beneficial, especially since the likelihood of exacerbating the problem is virtually nonexistent,” Kletechka remarked.