Nuclear one-two punch could knock out dangerous asteroid

Destroying a dangerous asteroid with a nuclear bomb is a well-worn trope of science fiction, but it could become reality soon enough.
Scientists are developing a mission concept that would blow apart an Earth-threatening asteroid with a nuclear explosion, just like Bruce Willis and his oilmen-turned-astronaut crew did in the 1998 film "Armageddon."
But unlike in the movie, the spacecraft under development — known as the Hypervelocity Asteroid Intercept Vehicle, or HAIV — would be unmanned. It would hit the space rock twice in quick succession, with the non-nuclear first blow blasting out a crater for the nuclear bomb to explode inside, thus magnifying its asteroid-shattering power.

"Using our proposed concept, we do have a practically viable solution — a cost-effective, economically viable, technically feasible solution," study leader Bong Wie, of Iowa State University, said Wednesday at the 2012 NASA Innovative Advanced Concepts (NIAC) meeting in Virginia. [ 5 Reasons to Care About Asteroids ]
When, not if 
Earth has been pummeled by asteroids throughout its 4.5 billion-year history, and some of the strikes have been catastrophic. For example, a 6-mile-wide (10 kilometers) space rock slammed into the planet 65 million years ago, wiping out the dinosaurs.
Earth is bound to be hit again, and relatively soon. Asteroids big enough to cause serious damage today — not necessarily the extinction of humans, but major disruptions to the global economy — have hit the planet on average every 200 to 300 years, researchers say.
So humanity needs to have a plan in hand to deal with the next threatening asteroid, many scientists stress.