LOS ANGELES — NASA launched a spacecraft Tuesday night on a mission to smash into an asteroid and test whether it would be possible to knock a speeding space rock off course if one were to threaten Earth.

The DART spacecraft, short for Double Asteroid Redirection Test, lifted off from Vandenberg Space Force Base atop a SpaceX Falcon 9 rocket in a $330 million project with echoes of the Bruce Willis movie “Armageddon.”

It will hit Dimorphos at 15,000 mph in September 2022 if all goes according to plan.

“This isn’t going to destroy the asteroid. It’s just going to give it a small nudge,” said mission official Nancy Chabot of Johns Hopkins Applied Physics Laboratory, which is managing the project.

Dimorphos is orbited by Didymos an asteroid much bigger than it. These two asteroid pairs are not dangerous to Earth, but they provide scientists with a method to determine the impact of collisions.

Dimorphos orbits Didymos once every 55 minutes, for an average of 11 hours. DART’s goal is a crash that will slow Dimorphos down and cause it to fall closer toward the bigger asteroid, shaving 10 minutes off its orbit.

Telescopes located on Earth will measure the change in orbital period. For the mission to be considered successful, it must change by 73 seconds.

DART could be used to alter the trajectory of an asteroid before it strikes Earth.

A small nudge “would add up to a big change in its future position, and then the asteroid and the Earth wouldn’t be on a collision course,” Chabot said.

Scientists are always looking for asteroids, and they plot their routes to see if any of them could reach the planet.

“Although there isn’t a currently known asteroid that’s on an impact course with the Earth, we do know that there is a large population of near-Earth asteroids out there,” said Lindley Johnson, planetary defense officer at NASA. “The key to planetary defense is finding them well before they are an impact threat.”

DART will need 10 months for the pair of asteroid pairs to be reached. It will happen at 6.8 million miles away from Earth.

DART will launch a small observation spacecraft from the Italian space agency ten days before. It will be followed by DART.

DART will broadcast video from the moment it’s destroyed by impact. The trailing craft will then take images of the impact area and any material being ejected three minutes later.