CAPE CANAVERAL, Florida (AP) — A NASA spacecraft closed in on an asteroid at blistering speed Monday in an unprecedented dress rehearsal for the day a killer rock menaces Earth.

The galactic grand slam was set to occur at a harmless asteroid 7 million miles (9.6 million kilometers) away, with the spacecraft named Dart plowing into the rock at 14,000 mph (22,500 kph). Scientists expected the impact to carve out a crater, hurl streams of rocks and dirt into space and, most importantly, alter the asteroid’s orbit.

Telescopes around the world and in space were poised to capture the spectacle. Though the impact should be immediately obvious — with Dart’s radio signal abruptly ceasing — it will be days or even weeks to determine how much the asteroid’s path was changed.

The $325 million mission is the first attempt to shift the position of an asteroid or any other natural object in space.

“No, this is not a movie plot,” NASA Administrator Bill Nelson tweeted earlier in the day. ”We’ve all seen it on movies like ‘Armageddon,’ but the real-life stakes are high,” he said in a prerecorded video.

Monday’s target: a 525-foot (160-meter) asteroid named Dimorphos. It’s actually a moonlet of Didymos, Greek for twin, a fast-spinning asteroid five times bigger that flung off the material that formed the junior partner.

The pair have been orbiting the sun for eons without threatening Earth, making them ideal save-the-world test candidates.

Launched last November, the vending machine-size Dart — short for Double Asteroid Redirection Test — navigated to its target using new technology developed by Johns Hopkins University’s Applied Physics Laboratory, the spacecraft builder and mission manager.

A mini satellite followed a few minutes behind to take photos of the impact. The Italian Cubesat was released from Dart two weeks ago.

The non-profit B612 Foundation, dedicated to protecting Earth from asteroid strikes, has been pushing for impact tests like Dart since its founding by astronauts and physicists 20 years ago. Monday’s dramatic action aside, the world must do a better job of identifying the countless space rocks lurking out there, warned the foundation’s executive director, Ed Lu, a former astronaut.