Gravity-Powered Asteroid Tractor Proposed to Thwart Impact

An asteroid the size of two football fields could wipe out a large city or set off a series of tsunamis across the world. The threat of such an Earth-smashing asteroid has lead scientists to dream up several methods of defending the planet against such a catastrophe. Solutions have ranged from pushing the asteroid with a spacecraft to mounting a thruster on its surface. But pushing it would require too much fuel and could break up the asteroid. Also, asteroids rotate, which could complicate the firing of a surface thruster. Now, two NASA astronauts have presented a plan for an “asteroid tractor”—an unmanned, 20-ton spacecraft that uses the invisible bond of gravity to gently pull an asteroid into a new, non-threatening orbit.