This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Asteroids don't come with a warning label that they might one day hit Earth. While we don't know of any currently on course to do so, we are finding thousands of new ones each year, and there's always a chance that one could.
We proved a viable technique for dealing with that possibility: The DART mission successfully moved a small asteroid using a "kinetic impactor"—basically a big rod designed to push the asteroid off its trajectory. But DART had one big flaw: It was traveling in the same direction as the asteroid and approached it from behind, eventually hitting it with an impactor launched while in orbit around it. That technique might work if we have enough warning, but it would require years of orbital maneuvers.
An alternative proposed by researchers at Beihang University is to use a new type of solar sail to deflect a potentially hazardous asteroid by hitting it head-on. The work is published on the arXiv preprint server. Deflecting an asteroid using an impactor comes down to one simple factor: energy.
The more energy transferred from the impactor to the asteroid, the more the asteroid will move. And the thing about energy is that it increases with the square of velocity. In other words, the faster you hit something, the more energy you impart to it.
DART smashed into Dimorphos, its target asteroid, at about 6 km/s—a respectable speed, but one limited by the fact that it was coming from the same direction. According to the new paper, an impactor using a solar sail could approach an asteroid from the opposite direction—akin to a wrong-way highway driver—and smash into its target at around 100 km/s, imparting something like 230 times the energy per kilogram of impactor mass that the DART test did. The problem is getting the spacecraft moving in the opposite direction.
Almost everything orbits the sun counterclockwise, including Earth. As such, when something launches from Earth, it's already moving that way. Reversing direction and entering a clockwise (retrograde) orbit requires a lot of energy, to put it mildly.
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