Space junk: why is it a problem and what are we doing about it?

News / Shannon Ryan / February 21, 2024

Humans are putting objects into space faster than ever before. As a result, space is becoming increasingly polluted with junk, raising the risk of catastrophic collisions in orbit.

Deakin University’s Applied AI Institute (A2I2) is helping spur research in spacecraft protection against debris with the release of the world’s largest open-source database and code repository of hypervelocity impact data, collected from over 15 years of Whipple shield (a type of debris shielding used on spacecraft) impact testing.

Access the hypervelocity impact data repository HERE


Key points:

  • We are launching objects into space at a never-before-seen pace
  • As a result, the risk of collisions between space junk is rapidly increasing
  • Spacecraft require armour for protection against debris impacts
  • To slow the rate of space pollution, operators are deorbiting their satellites at the end of their mission – resulting in more space junk hitting the Earth
  • Policies and guidelines are being developed by national and international groups while Australia faces ongoing delays


The emergence of small satellite technology, cheaper launch costs, and the emergence of mega-constellations such as SpaceX’s Starlink (of which there are already almost 9,000 satellites) we are putting objects into orbit faster than ever before. Since 1957 there have been around 16,000 objects launched into space – one-third of those have occurred in the past 3 years alone.


AI simulation video of hypervelocity impact shows a 2.8mm sphere exploding through space shielding.
This simulation from Fraunhofer EMI shows how damaging hypervelocity impact can be. (Fraunhofer EMI)


As a result, areas of space that have the most commercial, scientific, and Defence value are becoming increasingly crowded, raising the possibility of collisions between orbiting objects.

It doesn’t take much to cause a catastrophic impact. Because objects orbit at such high speeds, pieces of space junk as small as 1 cm (of which there are estimated to be 1 million) have as much energy as a hand grenade – posing a catastrophic risk to even the International Space Station.

Space junk is already one of the biggest risks for any space mission. Larger satellites and spacecraft that carry human astronauts already require armour to protect them from impact of small pieces of space junk. Deakin’s Applied AI Institute (A2I2) is helping here – by applying machine learning and artificial intelligence to improve the performance of spacecraft armour. We’ve also recently compiled and shared the world’s largest space debris impact database and built an open-source code repository that can be used to design spacecraft armour.


Left: impact of a 1.2 cm aluminium sphere at 7000 m/s, simulating a space junk impact on a thick aluminium plate. Right: an example of spacecraft ‘armour’ – a Whipple shield, where the space junk particle is disrupted by an outer sacrificial plate and fragmented into a cloud of smaller molten and vapourised particles.


After 70 years of neglect, national space agencies, commercial space operators, and international bodies such as the United Nations are beginning to take the preservation of the space environment more seriously.

Unfortunately, there are no solutions that are easy or will be cheap. One measure involves removing satellites from orbit at the end of their mission by forcing them to re-enter the Earth’s atmosphere – where they typically burn up before reaching the Earth’s surface.

Astroscale, a Japanese startup with a mission to clean up the space environment, recently launched its ADRAS-J spacecraft with funding from the Japanese Space Exploration Agency (JAXA). Although it won’t remove anything this mission, rather focusing on manoeuvring close to a defunct Japanese rocket upper stage, the follow-up mission ADRAS-J2, aims to capture and de-orbit a debris body.

Although removing debris, particularly large pieces of debris in the most polluted orbits, will help, space junk can sometimes survive re-entry and impact upon the Earth’s surface – mainly land masses in the southern hemisphere.

Since May last year there have been three separate instances in Australia related to space junk re-entering the Earth’s atmosphere.

On August 7th, 2023, a Russian Soyuz-2 rocket body re-entered the Earth’s atmosphere and broke up above southeast Australia, providing a spectacular light show for residents in Victoria and Tasmania.

In mid-July 2023, a large metal object from the third stage of an Indian Polar Satellite Launch Vehicle (PSLV) washed up on shore 250 km north of Perth in Western Australia.

In May 2022 three pieces of debris from a SpaceX Crew Dragon capsule were found in New South Wales farmland.

Although no fatalities have ever been recorded from someone being struck by a piece of space junk, a study in 2022 predicted a 10% probability of casualties in the next decade [1].


This first high-resolution image, taken on the first day of the Artemis I mission, was captured by a camera on the tip of one of Orion’s solar arrays. The spacecraft was 57,000 miles from Earth when the image was captured, and continues to distance itself from planet Earth as it approaches the Moon and distant retrograde orbit.
Image: NASA – This first high-resolution image, taken on the first day of the Artemis I mission, was captured by a camera on the tip of one of Orion’s solar arrays. The spacecraft was 57,000 miles from Earth when the image was captured, and continues to distance itself from planet Earth as it approaches the Moon and distant retrograde orbit.


Where does Australia sit in all this? We provide critical inputs to international space surveillance efforts via the Space Surveillance Telescope (SST) at Exmouth and the Western Australia Space Radar (WASR) from LeoLabs. Under the AUKUS defence agreement a new tracking radar for deep space surveillance will be built in Exmouth.

In terms of managing the space environment, the Australian Space Agency requires that all Australian objects going to space provide a ‘debris mitigation strategy’. However, to date, Australia has no national space debris policy, instead requiring the use of international guidelines and standards.

A national Space Situational Awareness roadmap, expected to have been released by the space agency in 2021 for implementation beginning in 2022 [2], is still pending.


A/Prof Shannon Ryan, Head of Defence and Space Research at Deakin’s Applied AI Institute, is Australia’s leading expert in hypervelocity impact (ranked 3rd globally).





[1] M Byers, E Wright, A Boley, C Byers, “Unnecessary risks created by uncontrolled rocket reentries”, Nature Astronomy; 6: 1093-1097, 2022

[2] A Vignelles, M Le Pellec, F Gallagher, “The Australian Space Agency’s inaugural Space Situational Awareness technology roadmap: Context, methodology and learning”, Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS), Maui, 2021



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