Shoot with a rocket


"We're talking about an interstellar bullet," says space hardware specialist Mark Fittock, who is working on the planetary defense mission.


"We're not going to try to go into orbit or anything, DART will work." The DART, or double asteroid redirection test, is NASA's first planetary defense mission.

The purpose of the mission: see if it can move the giant rock off course. The DART asteroid is destined for Didymos, a huge piece of space rock about 800 meters in diameter and about 11 million kilometers from Earth.

Didymos is well out of the way of our planet so it is a perfect place to test our new defense technology.

He is holding a smaller rock – affectionately dubbed Didymoon – in its orbit. This is the only humanity that will punch.

Our current options, if we find a rock in our way, include firing nuclear-tipped missiles. But attempting to blow up an asteroid is an unpredictable game, with large chunks – now radioactive – likely to spread and enter the atmosphere, a familiar backdrop for anyone who has watched the 1998 games. Deep Impact.

DART represents a more subtle solution. It's tiny. It measures only 12.5 meters by 2.4 meters with fully extended solar panels and weighs about 500 kilos. On board is just the technology needed to acquire and track your target. Think of it as an interstellar cruise missile.

Given its small size, even reaching Didymoon at high speed – about six miles per second, often faster than a bullet at high speed – will not mess around much in the rock.

But that does not have to. Even a small divergence in the path of an asteroid can make a huge difference over the vast distances of space.

Mark Fittock did a double degree at Monash University in astrophysics and mechanical engineering.

Mark Fittock did a double degree at Monash University in astrophysics and mechanical engineering.Credit:DLR

Fittock is a student at Monash University who worked on NASA's InSight landing module, which was left behind on Mars in 2018. He now works as a space systems engineer for the OHB System in Germany, designing DART's sister mission, HERA.

The HERA, which is being built by the European Space Agency, will be launched for Didymos a few years after DART. It contains a set of tools that scientists will use to assess how much the impact of DART has changed Didymoon.

The HERA will scan Didymoon using laser technology.

The HERA will scan Didymoon using laser technology. Credit:ESA / Provided

"Let's take a look – what kind of craters are there, what kind of damage was caused? That will give us a better idea of ​​what we can do if an asteroid goes to Earth, "says Fittock.


Perhaps the most important calculation that HERA will try to do is how hard you need to punch the asteroid, and with how much weight behind the blow, to knock it off course?

Building a big rocket takes a lot of time, and we can just take a chance. Knowing that we could knock down the rock with a smaller, faster probe to build, we could get several shots.

"If we go smart with what we hit, we can hit it with something smaller, but for the better," says Fittock.

"If this was really happening and we had to interrupt it, we do not know much about our options at the moment. We know we could achieve something, but we do not know what to hit."

Liam is The Age and science reporter for the Sydney Morning Herald

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