It feels like science fiction, but NASA is preparing a mission to deflect its first asteroid.

Twenty-one years after Bruce Willis saved the Earth from a fictional asteroid in Armageddon, NASA is planning a real-life asteroid collision. It’s the first test in a project to, if needed … yes, really, save the Earth from huge deadly space rocks.

In a detailed description of the mission last week, NASA confirmed that the Double Asteroid Redirection Test (DART) aims to slam a spacecraft into the surface of Didymos B, a small asteroid orbiting a larger asteroid called Didymos A.

The collision is scheduled for September 2022. Elon Musk’s SpaceX has been contracted to launch the mission in June 2021 using its Falcon 9 rocket. After that, DART will make its way to Didymos using solar-electric propulsion charged by onboard solar arrays. It will hit Didymos B at approximately 21,600 kilometres per hour.

Asteroids are dangerous not just because they are large (often more than 100 metres wide) but because any that collide with Earth will do so at enormous speeds. That will give them enormous destructive energy.

The DART project is the first space test in NASA’s search to understand how to push a threatening asteroid off course before it hits the Earth. As long we spot any threatening asteroid early enough, just tiny deflections will ensure it sails harmlessly past Earth.

Unlike Armageddon’s nuclear scenario, DART will use just the kinetic energy of its own impact to move Didymos B.

But like Armageddon, DART will deliver images of the impact – through both an onboard camera and via a shoebox-sized ‘ride-along’ satellite that will be released before DART smashes into Didymos. (And if you think those movie jokes are out of line with the seriousness of the mission, consider this: NASA has called the onboard camera DRACO, after either the Harry Potter character or the James Bond henchman.)

NASA said the Didymos system itself poses no threat to Earth, but is an ideal test site. Targeting a double-asteroid system will let NASA make the most precise possible observations of the DART spacecraft’s impact.

Nobody quite knows what will happen when the impact occurs. Didymos is just a point of light in telescopes, and researchers aren’t sure whether it’s composed of solid rock, loose rubble or something softer, more akin to sand, that might lessen the force of the impact.

DART is a key step in the larger project of NASA’s Planetary Defense Coordination Office, formed in 2016 to lead responses to “near-Earth orbit impact hazards” – that is, giant Earth-threatening asteroids.

Earlier this month the PDCO, NASA, the European Space Agency (ESA) and other agencies also completed a drill simulating how a planetary emergency would play out if Earth was hit by an asteroid of the right size – that is, one not big enough to just wipe us out.