New theory: A lick of paint can deflect an asteroid

By Paul Harper

Image / Thinkstock
Image / Thinkstock

Forget Bruce Willis detonating a nuclear bomb to deflect an Earth-bound asteroid - all you need to do to divert an oncoming space rock is give it a lick of paint.

That's the plan put forward by Dave Hyland, a professor of physics and astronomy and also a faculty member in the aerospace engineering department at Texas A&M University.

While the idea sounds out-of-this-world, NASA is getting involved and wants to know more.

What Hyland proposes is a process called "tribocharging powder dispensing" - as in high pressured - spreading of a thin layer of paint on an approaching asteroid, such as the 2012 DA14 which came within 27,350km earlier this month.

The paint changes the amount of sunlight the asteroid reflects, Hyland theorises, resulting in a change in what is called the Yarkovski effect. This force arises because on a spinning asteroid, the dusk side is warmer than the dawn side and emits more thermal photons, with each photon carrying a small momentum.

Hyland theorises that the unequal heating of the asteroid will result in a net force strong enough to shift the asteroid from its current orbit, so it hurtles safely past Earth.

However, you can't paint an asteroid with run-of-the-mill house paint, Hyland says.

"It could not be a water-based or oil-based paint because it would probably explode within seconds of it entering space," he says.

"But a powdered form of paint could be used to dust on the asteroid and the sun would then do the rest. It cures the paint to give a smooth coating, and would change the unequal heating of the asteroid so that it would be forced off its current path and placed on either a higher or lower orbit, thus missing Earth."

Hyland insists there is logic behind the idea.

"I have to admit the concept does sound strange, but the odds are very high that such a plan would be successful and would be relatively inexpensive. The science behind the theory is sound. We need to test it in space."

A former student of Hyland's Shen Ge, has solved the puzzle of how to get the paint of the oncoming asteroid. Rather than using a giant paint roller, a "tribocharging powder dispenser" would spray a mixture of inert gas and charged dry-paint powder at the asteroid that would attract the powder to its surface through electrostatics. Solar wind and UV radiation would then cure the powder, giving a smooth, thin coat on the surface.

"The tribocharged powder process is a widely used method of painting many products," Hyland says. "It remains only to adapt the technology to space conditions."

NASA has approached Hyland for developing the project to test the theory.

"There are thousands of asteroids out there, and only a small percentage of them are known and can be tracked as they approach Earth," Hyland says.

"The smaller ones, like DA14 are not discovered as soon as others, and they could still cause a lot of damage should they hit Earth. It is really important for our long-term survival that we concentrate much more effort discovering and tracking them, and developing as many useful technologies as possible for deflecting them."

The next known near-Earth asteroid is Apophis, passing Earth at a distance of 30,000km in 2029, before returning again in 2036, when astronomers predict it has a one-in-200,000 chance of smashing into Earth.


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