Deflection of near-Earth asteroids by kinetic energy impacts from retrograde orbits

Previous studies of non-nuclear diversion of near Earth asteroids have largely ignored the use of pure kinetic energy impacts, partly due to apparent limits on impact speeds of 10-. Here, I will consider the use of a near-term solar sail to deliver an inert projectile onto a retrograde solar orbit, thus raising impact speeds to at least . Such high-energy orbits increase the energy liberated during impact by a factor of 40 or more, while reducing the required projectile mass by at least 95%. This considerable reduction in projectile mass allows kilometre-sized asteroids to be diverted with current launch vehicles, near-term technologies and at a cost comparable to a modest deep space mission.