It's one of those nagging problems science has yet to solve: how do we save Earth if one of our asteroid neighbors starts heading our way? We've noodled everything from tractor beam, lasers, and even nuking them Armageddon style. A new proposal joining the chorus suggests hitting asteroids with white paintballs could do the trick — first by steering them off course with the force of impact, then by using the force of reflected sunlight bouncing off the paint to slowly move the offender out of the way.
As you've guessed this won't be just a few paintballs, but a virtual asteroid redecoration with a blast of an estimated five tons of white paint. It's easy to understand how the impact of five tons of anything might move an asteroid along, so why add paint?
Sung Wook Paek, a graduate student in MIT's Department of Aeronautics and Astronautics came up with the concept and did the math using the asteroid Apophis, which could buzz us in 2029, to explain how his theory would work.
Apophis is a whopping 27-gigatons, and 1,148 feet in diameter. He used those calculations to determine two blasts of pellets (five tons in total) launched from a spacecraft would coat both sides of the asteroid as it rotates. The entire surface would get about a five-micrometer-layer of paint, doubling the reflectivity of the surface. This gives the solar radiation pressure — or the force placed on objects by the sun's photons — extra oomph that could gradually move the asteroid. And by gradually, he means over 20 years or so.
It is clearly a long-term plan, with his calculations putting the idea out of range to help with the 2029 pass. Despite this, Paek's proposal was still the winning entry in this year's Move an Asteroid Technical Paper Competition sponsored by the United Nations' Space Generation Advisory Council. According to MIT he also earned a nod from NASA, which called the plan "an innovative variation" on a method used by others to capitalize on solar radiation pressure.
If you are worried about that missed opportunity to blast Apophis in 2029, it's important to note that in the "blast an asteroid" game most of the ideas are long-term plays as they require additional thinking and technology development. So yes — barring some breakthrough we'll be chancing that one.
Paek is not resting on his laurels — he is still refining his idea. He proposes building the paintballs in space in case they rupture during a traditional Earth takeoff. He also theorizes the paint pellets could be revised to use aerosols to release puffs of air creating drag to slow down the asteroid, or, if sticking with the paintballs, he notes a coating could serve as a way to make sometimes well-hidden asteroids more visible and easier to track.
Paek's unique plan and continued thinking illustrates that he, along with other scientists, are earnestly working on what we might do when the next asteroid comes around. The results may be long term, but the thinking and development has to start somewhere since there are plenty of asteroids lurking around out there.
The video below illustrates how Paek's plan could work.