Shoot with a rocket

"We're talking about an interstellar ball," said space equipment specialist Mark Fittock, who works on the global defense mission.

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"We will not try to put ourselves into orbit or anything, and DART will put it right there." DART, or asteroid redirection test, is NASA's first global defense mission.

The objective of the mission: to see if it can move the giant rock off the course. The DART asteroid targets Didymos, a huge block of space rocks about 800 meters in diameter and about 11 million kilometers from the Earth.

Didymos is well outside the path of our planet, so it's a perfect place to test our new defense technology.

He holds a smaller rock – dubbed affectionately Didymoon – in its orbit. That's the one humanity is going to hit.

Our current options, if we spot a rock that is heading towards us, include nuclear missile fire. But trying to blow up an asteroid is an unpredictable game, with the possibility that large chunks – now radioactive – are dispersing and entering the atmosphere, a scenario familiar to anyone who watched the years 1998 Deep impact.

DART represents a more subtle solution. It is tiny. It measures only 12.5 meters by 2.4 meters with fully deployed solar panels and weighs around 500 kg. On board, all that's left is the technology to acquire and follow its target. Think of it as an interstellar cruise missile.

Given its small size, even hitting Didymoon at high speed – about six kilometers per second, several times faster than a fastball – will not move the rock much.

But it is not necessary. Even a small divergence on the path of an asteroid can make a huge difference over the vast distances of space.

Mr. Fittock is a former Monash University veteran who worked on NASA's InSight lander, who landed on Mars in 2018. He is now working as a space systems engineer for OHB System in Germany, where he designed the sister mission HERA of DART.

HERA, built by the European Space Agency, will be launched for Didymos a few years after DART. It contains a series of instruments that scientists will use to determine the impact of DART's impact on Didymoon.

"Let's take a look – what types of craters are there, what damage have been done? This will give us a better idea of ​​what we can do if an asteroid moves towards Earth, "said Fittock.

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Perhaps the most important calculation that HERA will try to make is how hard it is to hit an asteroid and how much weight behind it, to make it fall off course?

Building a big rocket takes a lot of time and we are likely to receive only one hit. Knowing we could scare the rock with a smaller, faster-to-build probe means we would have more shots.

"If we are smart with what we have found, we could do it with something smaller but for a better effect," said Fittock.

"If it really happened and we had to stop, we do not know much about our options at the moment, we know we could hit something, but we do not know how to do it."