The fastest way to deflect an asteroid away from Earth would be to send a nuclear bomb aboard a spacecraft, a la the film Deep Impact, though we'd still need several years' warning.rnThe spacecraft would have to be able to home in on the asteroid and to trigger the explosion at just the right distance. Precision is needed to avoid breaking up the hurtling rock while still giving it enough of a nudge to prevent the Earth impact years down the line.rnThat assumes we're already prepared. Designing and building new spacecraft typically takes a few years. With current rocket technology, it would probably take several additional years to reach a threatening asteroid. And since the explosion would need to occur years ahead of the predicted impact in order to make the asteroid miss Earth, we'd need decades of lead time if we hoped to deflect Armageddon.
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