How could we protect the Earth against a deadly comet impact?
A number of methods have been proposed over the years including the famous one of sending nuclear-tipped rockets to explode either next-to, or inside the surface of the approaching body. Also, laser beams reflected from orbiting mirrors have been proposed to heat the surface of the body and provide a ‘jet’ of gas to act as a rocket on the body itself. Despite many technical and dynamical studies, no one really knows what the optimal method would be for a body of a given mass. Much depends on how much warning is available, and whether the strategy should be to pulverize the object, or to gently divert its course with a ‘mid-course’ correction. The biggest problem is determining which size of bomb is appropriate for a comet or asteroid of a particular composition and mass, and where to explode the bomb. If the explosion is delivered right to the surface, too small a blast will dig a crater and not provide enough course change if the comet/asteroid is detected too late. Too big an explosi
