October 28, 2012

Cosmic propaganda alert! Asteroids headed to Earth could be diverted with paintballs, says PhD student

Given sufficient warning, an asteroid headed on a collision course with Earth could be diverted by firing paintballs at it, an MIT graduate student has calculated. 
While the idea might seem facetious or amusing on its face, it was good enough for Sung Wook Paek of MIT's department of aeronautics and astronautics to win the 2012 Move an Asteroid Technical Paper Competition sponsored by the United Nations' Space Generation Advisory Council, which solicits creative solutions from young professionals. Paek presented his paper this month at the International Astronautical Congress in Naples, Italy.

Paek's proposal would work on two different levels. The paintballs themselves would impart a slight momentum change to the incoming asteroid, diverting it slightly -- but probably not enough to avoid a collision. But using white paint or other light color in the paintballs would increase the asteroid's albedo, or reflectivity. The pressure of photons of sunlight bouncing off the asteroid could, over time, provide a much greater shift in course. A similar effect is behind using solar sails for spacecraft: Light striking the sails and being reflected would provide impetus to move the craft.

Paek calculated the effects of the actions on the course of the asteroid Apophis, a 27-gigaton rock that is expected to come close to the Earth in 2029 and again in 2036. He calculated that 5 tons of paint delivered in two bursts, one on each side of the rock, would cover the asteroid, which has a diameter of 1,480 feet. His calculations show that over a period of 20 years, light from the sun would shift the path of the asteroid enough to avoid a collision.

In his paper, Paek noted that launching the paintballs in a conventional rocket would probably not be a good course of action -- the increased gravity of acceleration would probably burst them all. Instead, he proposed that the paintballs be assembled in orbit, probably at the International Space Station. Painting the asteroid, he noted, would also make it easier to track from Earth. 

by: Thomas H. Maugh II


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