Asteroids Deflected with Paint

Asteroids Deflected with Paint

Here is another one of those ideas that makes me say, “Why didn’t I think of that?” Just last month a graduate student presented a paper at the International Astronautical Congress in Naples, Italy. Sung Wook Paek in the Department of Aeronautics and Astronautics at MIT, came up with the idea of firing paint balls at an asteroid headed for a collision with Earth.

This paper won the 2012 Move an Asteroid Technical Paper Competition sponsored by the United Nations’ Space Generation Advisory Council, a competition which solicits creative solutions from young professionals.

Idea behind the paint balls is, given sufficient warning an asteroid could be diverted by increasing the asteroid’s albedo, or reflectivity.

Thus, the paint would have to be light-colored and applied to the asteroid with sufficient advanced notice to allow solar pressure to divert the large body’s trajectory enough to bypass Earth. Paek suggested that his plan would work in two different ways.

Paintballs themselves could impart a slight momentum change to the asteroid, diverting it only slightly, but not enough to avoid Earth. The main effect would come from the paint’s increase in reflectivity on the asteroid.

Thus, the pressure of photons coming from the sun, acting over enough time, could result in a large shift in course. Paek concluded that the course of asteroid Apophis, a 27-gigaton rock that is expected to pass close to Earth in 2029 and in 2036, could be changed enough to miss Earth. He estimated that 5 tons of paint would be sufficient to cover the 1,480-foot-diameter asteroid.

Such asteroids are known as Near-Earth Objects (NEOs) that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth’s neighborhood.

These asteroids were generally formed in the solar system between the orbits of Mars and Jupiter. Astronomers believe these NEOs are bits and pieces left over from the initial agglomeration of the inner planets that include Mercury, Venus, Earth, and Mars.

Paek’s calculations indicate it will take roughly 20 years of exposure to the paint in order to deflect the asteroid away from an Earth collision. Now, let me see if I have this right.

The first close approach will be in 2029 and the paint has to be in place for 20 years. A quick calculation indicates that we have 7 years to send 5 tons of white paint to the asteroid, probably millions of miles distant from Earth, and apply the paint all over the rock.

Assuming this can be done, there remains a slight problem. No one can tell us with certainty, 20 years in advance, that if left alone the asteroid will in fact collide with Earth. So, if we were to mount a huge space program, likely to cost tens of billions of dollars, to send paint to Apophis, what are the possible outcomes?

Assuming we are successful in painting the rock, there will likely be a trajectory deflection. However, the critical question: “Will the asteroid be diverted away from or toward Earth?”

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