The idea is to increase an asteroid's reflection ability of sunlight and take advantage the force of bouncing photons to push an object off its course. To do so, Sung Wook Paek, a graduate student in MIT’s Department of Aeronautics and Astronautics, proposes to fire two rounds of paint-filled pellets from a spacecraft to cover objects such as asteroids in "blindingly white" color.
The initial force from the pellets could bump an asteroid off course, Paek said, but the sun’s photons would deflect the asteroid even more. However, this should not be considered an emergency procedure. In his paper, Paek calculated that the 27-gigaton, 1,480-ft diameter rock Apophis, which will be near earth in 2029 and in 2036, would need 5 tons of paint to be covered entirely with a five-micrometer-layer of paint.
The effect of solar radiation would not be seen immediately, but it would take about 20 years of solar radiation pressure to take the asteroid off its path. And there may be another problem. The "violent" takeoff of a rocket may not be suitable to deliver paintballs to an asteroid. Instead, Paek suggests making paintballs in space at space stations, from where spacecraft could pick up paintballs as needed.