Killer asteroids on a crash course with Earth aren't just for imaginative sci-fi movies. NASA recognizes rogue asteroids as a legitimate concern, so it's developing a mission called the Double Asteroid Redirection Test (DART).

The space agency on Friday announced that DARTis moving from concept development into a preliminary design phase and released a video showing how it might work.

DART is about testing out what NASA calls "the kinetic impactor technique." This means smashing a spacecraft into an asteroid to redirect it to a safer path. NASA is eyeing asteroid Didymos, which actually a pair of asteroids, Didymos A and the smaller Didymos B. Didymos B orbits around its larger friend. Didymos will be approaching Earth (from a safe distance) in both 2022 and 2024.

As the video shows, DART would launch, fly to the asteroids and aim itself at the smaller of the pair. "Then the refrigerator-sized spacecraft would strike the smaller body at a speed about nine times faster than a bullet, approximately 3.7 miles per second (6 kilometers per second)," NASA notes. Scientists on Earth would then observe the asteroid to see how its orbit around Didymos A has changed.

NASA tracks potentially dangerous asteroids classified as near-Earth objects. While we can keep an eye on these NEOs, we're still in the early phases of working out how to deal with an asteroid large enough to damage our planet. If DART is successful, it could become the blueprint for how to manage threatening asteroids.

"Since we don't know that much about their internal structure or composition, we need to perform this experiment on a real asteroid. With DART, we can show how to protect Earth from an asteroid strike with a kinetic impactor by knocking the hazardous object into a different flight path that would not threaten the planet," says DART investigation co-lead Andy Cheng of The Johns Hopkins Applied Physics Laboratory.

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Arizona-sized asteroid as seen by NASA (pictures)

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Here's how NASA plans to deflect an asteroid - CNET