How paintballing could save the Earth

Posted by Kate Taylor

Crazy as it sounds, an MIT scientist is proposing that, if a dangerous asteroid approaches the Earth, it could be deflected by firing paintballs at it.

If timed just right, they say, pellets full of paint powder could be launched in two rounds from a nearby spacecraft, more than doubling an asteroid's reflectivity, or albedo. The initial force from the pellets would bump it off course; and over time, the sun’s rays would deflect it even more.

Graduate student Sung Wook Paek used the asteroid Apophis - due to come close to Earth in 2029, and then again in 2036 - as a theoretical test case.

Paek says that five tons of paint would be enough to cover the asteroid, which has a diameter of 1,480 feet. A first round of shots would cover the front, and a second the back once the asteroid has rotated. As the pellets hit the asteroid, they would burst apart, splattering the surface with a fine, five-micrometer layer of paint.

After that, though, it would take up to 20 years for the cumulative effect of solar radiation pressure to successfully divert the asteroid from its Earthbound trajectory.

Lindley Johnson, program manager for NASA’s Near Earth Objects Observation Program, says Paek’s proposal is 'an innovative variation' on a method already used by others to exploit solar radiation pressure.
For example, the Messenger spacecraft, currently orbiting Mercury, is equipped with solar sails that propel the craft with solar radiation pressure, reducing the fuel needed to power it.

"It is very important that we develop and test a few deflection techniques sufficiently so that we know we have a viable ‘toolbox’ of deflection capabilities to implement when we inevitably discover an asteroid on an impact trajectory," he says.