A research team from the University of Leicester, UK, investigated exactly this problem, calculating the energy which would be required to sufficiently alter the course of a 1000 km diameter meteor hurtling towards Earth at 10 km per second. Their verdict can be summarised in just two words : “Sorry Bruce”.
“The conclusion is very simple. Our current level of technology is simply nowhere near sufficient to protect Earth from such an asteroid by this specific means of asteroid defence, though other possible methods have been suggested that may be more feasible.”
– say Back A., Brown G., Hall B. and Turner S. in their paper ‘P1_1 Could Bruce Willis Save the World?’ which is published in the peer-reviewed Journal of Physics Special Topics. Vol 10, No 1 (2011).
Note: The journal forms a module in the final year of the four-year MPhys degree and is designed to give students an insight into the formal process of submission, peer review and publishing. For more details see: Football on Mars and other improbable research