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Scientists turn to wind tunnels to predict where space debris will land

Written by Javed Iqbal

The sky-watching world was thrown into a spin this week with several reports of space debris falling on Australian farms.

Experts say that as more satellites go up, it’s only logical that more will come down.

Mark Rigby, a former curator of the Sir Thomas Brisbane Planetarium, agrees.

“The number of operational satellites has almost doubled in the last 18 months. That’s phenomenal,” he said.

But if you’re planning a “space junk” hunt, don’t get your hopes up.

“Fortunately, most of our Earth is covered by oceans. So most space debris actually falls down harmlessly, and a lot of space debris evaporates before it even reaches the surface of our planet,” Mr Rigby said.

But sometimes it lands in a cow fold.

James Stirton discovered wreckage from a rocket on his family property in south-west Queensland, near Quilpie, in 2008.

A large ball of space junk on display in a glass container
Stirton’s space junk is now on display at the Cosmos Center in Charleville.(Supplied: Cosmos Center)

At the time, he and his wife Sue were fielding calls from around the world and hosting visits from researchers eager to inspect the round fuel cell that landed near his cattle in the thicket.

“They checked it for radiation and wanted to take it away, and I said, ‘No, it’s staying here,'” he explained.

The space wreck, officially named 2006-047-C, lived in a farm shed until the couple retired.

It is now on permanent display at Charleville’s Cosmos Centre.

Stirton, ever the pragmatic farmer, said his discovery did not lead to any further spacecraft exploration on his property.

“It was during the drought years, so we had plenty of other things to do,” he said.

“And I figured it would only happen once in my life, so no, I never thought I’d find more space junk.”

But he did.

“A couple of years later we found another one,” he said.

“Actually, I don’t think we ever told anyone about the other find,” Mrs Stirton laughed.

Serious field of study

A specialist project at the University of Southern Queensland was launched earlier this year focusing on space debris.

“We’re starting to see more and more of this happening,” said Fabian Zander, senior researcher at the University of Southern Queensland.

A man stands next to a large machine with a round door
Fabian Zander uses wind tunnels to study “separation of objects in hypersonic flow”.(Provided by: University of Southern Queensland)

“I would like to hope there are not too many more [incidents] like SpaceX … but we need a better understanding of the death and dispersion of things re-entering the atmosphere.”

He said that while most controlled re-entries aim for the “space graveyard” in the South Pacific, some non-functional satellites can come down anywhere.

“Even the impact of the sun shining on the object can change the force and trajectory of it,” he explained.

“Earth’s atmosphere expands and contracts slightly depending on the weather.

“When something orbits the upper atmosphere, the effect is marginally different depending on the particular atmospheric conditions, and that cannot be predicted with any certainty at this stage.”

But he said there was no need to worry about being hit by “zombie” satellites when you stepped outside.

“There’s only been one person hit by space debris,” he said.

“A lady named Lottie Williams in the United States was hit by a piece on her shoulder and it didn’t hurt her at all.”

a man stands in front of a rocket
Mark Rigby says the chance of finding space debris is “pretty small”.(Provided by: Mark Rigby)

We’re hunting for space junk?

Sir. Rigby said the recent finds might inspire people to go hunting for debris, but the chances of finding anything were “pretty slim”.

“Even if you’re using satellite imagery to find the pieces of Skylab that came down in 1979, which are undoubtedly still out there, you’re trying to find things that might be a meter across—or even smaller—in a large country.

people gather in a fold with space junk, sheepdogs and a ute
Farmers Mick Miners and Jock Wallace, along with ANU astrophysicist Brad Tucker, visit a site in NSW where two pieces of space debris were found.(ABC South East NSW: Adriane Reardon)

“So I’ll say good luck to you.”

He also warned of the possible dangers.

“There may be space junk that has come down that still has some toxic material. With these things, it’s quite often best to contact the authorities if you found something you think is space junk.

“Get it checked first before you start handling it.”

And if you find something, don’t get too attached to it.

“It still belongs to the country of origin,” Mr Rigby said.

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Javed Iqbal

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