PLANETARY SECURITYCan We Really Deflect an Asteroid by Crashing into It? Nobody Knows, but We Are Excited to Try

By Stefania Soldini

Published 23 September 2022

Nasa’s Double Asteroid Redirection Test (Dart) spacecraft is designed to be a one hit wonder. It will end its days by crashing into an asteroid at 24,000 kilometers per hour on 26 September. Launched from Earth in November 2021, Dart is about the size of a bus and was created to test and prove our ability to defend the Earth from a dangerous asteroid.

Nasa’s Double Asteroid Redirection Test (Dart) spacecraft is designed to be a one hit wonder. It will end its days by crashing into an asteroid at 24,000 kilometers per hour on 26 September. Launched from Earth in November 2021, Dart is about the size of a bus and was created to test and prove our ability to defend the Earth from a dangerous asteroid.

Landing a direct hit on a target from 11 million kilometers away isn’t easy. But while this sounds far, the asteroid was actually selected by Nasa because it is relatively close to Earth. This will give engineers the opportunity to test the spacecraft’s ability to operate itself in the final stages before the impact, as it crashes autonomously.

The target asteroid is called Dimorphos, a body 163 meters in diameter that’s orbiting a 780 meter-wide asteroid called Didymos. This “binary asteroid system” was chosen because Dimorphos is in orbit around Didymos, which makes it easier to measure the result of the impact due to the resulting change in its orbit. However, the Dimorphos system does not currently pose any risk to the Earth.

Regardless, Nasa is attempting nothing less than a full scale planetary defense experiment to change an asteroid’s path. The technique being used is called “kinetic impact”, which alters the orbit of the asteroid by crashing into it. That’s essentially what is known as a safety shot in snooker, but played on a planetary level between the spacecraft (as the cue ball) and the asteroid.

A tiny deflection could be sufficient to prove that this technique can actually change the path of an asteroid on a collision path with the Earth.

But the Dart spacecraft is going to be completely blown apart by the collision because it will have an impact equivalent to about three tons of TNT. In comparison, the atomic bomb dropped on Hiroshima was equal to 15,000 tons of TNT.

So, with this level destruction and the distance involved, how will we be able to see the crash? Luckily, the Dart spacecraft is not travelling alone on its quest, it is carrying LICIACube, a shoebox-size mini spacecraft, known as a cubesat, developed by the Italian Space Agency and aerospace engineering company Argotec. This little companion has recently separated from the Dart spacecraft and is now travelling on its own to witness the impact at a safe distance of 55km.