While we might all be aware of the issues of rubbish, trash, debris, or similar in our locale, few of us think about how litter-filled space is. It’s a growing issue that concerns many experts, not least because of the potential threat of the so-called Kessler Syndrome. If Kessler’s idea came about, it would lead to an unstoppable cascade of collisions. While that’s an extreme worst-case scenario, it’s essential to understand precisely what pieces of debris in space can lead to and devise methods to reduce the issue.
Read on while we look at how to solve a problem like space debris. We also explain thoroughly what the definition of the material is.
What is space debris?
Space objects or debris is any human-made object left behind by a mission. This can mean larger pieces, such as old satellites or parts of rockets used in the past. It can also constitute fragments of destroyed or decayed spacecraft. However, space debris can also be more minor items that are dust-sized or above. While dust may not seem like an issue individually, anyone who has fallen behind on their housework can attest that dust soon accumulates to a more noticeable number over time. Leaving space debris unmaintained can become dangerous.
How much space debris is there?
NASA estimates there are around 27,000 human-made objects larger than 10 centimetres. This typically involves items that are left behind from past space missions. A 10-centimetre object may not sound dangerous, but it’s large enough to cause an entire spacecraft to disintegrate due to the speeds involved in such a collision. Besides those sized pieces, NASA also believes that the number of smaller pieces of space junk runs into the hundreds of millions.
Ultimately, such numbers are conservative estimates, with the figure likely to be much higher. With private corporations such as SpaceX and Virgin Galactic setting up their own private space flight journeys, more debris is expected to occur. Previously, certain areas were considered “blind spots,” making it harder to detect where fragments and dust may reside.
How do space agencies track debris?
It’s essential to know how much space debris orbits Earth to understand what a big issue it is. Endeavours such as LeoLabs have worked to detect some of these blind spots. In 2019, it built a space radar in New Zealand to pick up blind spots in the Pacific region.
NASA and the US Department of Defense have a highly accurate satellite catalogue of objects in Earth’s orbit. It divides collision risks into three categories depending on the size of the threat involved.
How to clean space debris?
Knowing how to clean up space debris is increasingly vital in a world where space technology is becoming more widespread. The International Space Debris Coordination Committee (IADC) works to create cooperation in space debris research, appreciating that this is a global issue that needs unity to solve it. It recommends that each mission has a debris mitigation management plan.
The UN has also released Guidelines for the Long-term Sustainability of Outer Space Activities. It emphasises that governments must ensure satellite operations don’t contribute to the space debris problem.
Besides the UN, NASA and the European Space Agency have had guidelines in place for the past 30 years to minimise the risk of debris. They recommend that end-of-life planning considers that no spacecraft should remain in orbit for longer than 25 years.
However, what specific measures can be implemented to solve space debris? Below is a selection of the main ways debris removal can be made possible and how it can be avoided.
Using edge AI to simplify the process
Artificial intelligence (AI) can be a way of managing space debris. Using AI like edge AI offers many advantages compared to traditional methods. It doesn’t need a comms link to communicate between a platform on Earth and the issue in space, enabling it to conduct its work in real time. That means no delay in getting feedback leading to quicker response times.
While something like edge AI means that you need more computing power on the satellite, that issue is becoming less of a problem over time as silicon microprocessors become more advanced and able to compute more efficiently. ARM processors with FPGA provide particularly optimal performance for AI processing. Recently, the Advanced Concepts Team at the European Space Agency has run competitions looking at edge AI and the origin of space debris, evaluating new ways of tackling the issue using AI.
Crucially, such systems can be local to the space debris rather than relying on people on the ground to tackle the issue. Over the years, AI has overtaken humans at various tasks, from playing games like Chess or Go to accurate image recognition, suggesting the right system can make much faster decisions than individuals working on clearing fast-moving space debris. Machine learning via dedicated embedded systems can also help with devices sent up into space with the sole purpose of removal and retrieval.
While implementing such a system, it could also cut down on the risk of objects in space becoming space debris. For instance, an embedded device with machine learning AI can provide real-time autonomous engine health monitoring for companies in various sectors, including marine, nuclear, aerospace, and defence. This typically involves sending satellites into space to clear existing space debris, but it could be a suitable trade-off.
Using digital twins to clear space debris
Digital twins are computer-modelled representations of something in the real world. They could help tackle the problem with some adjustments. They often need many sensors to convey real-world data to the digital equivalent accurately. It can be impractical to add physical sensors, so one alternative is to use virtual sensors for digital twins.
Whatever method is used, digital twins supply a dynamic and realistic model of the situation, that is, the space debris that needs to be removed. Constantly augmenting the simulation by transferring information to the other twin, anyone working on clearing debris orbiting at high speed can still keep up with the process. And this can too be supplemented with information from AI.
Digital twins can also enhance collision avoidance which moves us to a different way of handling space debris.
Mitigation techniques using edge AI
Edge AI doesn’t solely need to be used to remove space debris. It can also help other spacecraft avoid the issue. Through advanced collision avoidance technology, new spacecraft can avoid hitting old satellites and other objects that reside in space.
While there’s still the concern of the debris existing, it reduces the risk of a potentially catastrophic cascade of collisions and explosions, as suggested by the Kessler syndrome. Donald Kessler, NASA’s first senior scientist for orbital debris, addressed such a domino effect and indicated that if enough debris were disrupted, it could lead to the Earth’s orbit becoming unsafe and unusable—a horrific event for humankind.
Using harpoons or nets
As outlandish as it might sound, some companies have tried using harpoons or nets to capture space objects. In 2019, Surrey Satellite Technology successfully used a harpoon method to do so.
Japan’s Aerospace Exploration Agency developed a net with a fishing equipment company. The idea was that it could launch a satellite that deployed a 1,000-foot wire net that could then magically attract space junk. It would then return to Earth and burn up in the atmosphere. Such technology would require edge AI or other AI systems to figure out what were working space objects and what counted as pieces of debris.
Another plan has used a ground-based laser, known as a “laser broom”. Researchers at the Australian National University found that they could heat one side of a satellite, causing it to shift its orbit and be moved into Earth’s atmosphere safely.
One academic paper has suggested that operators must be encouraged to remove space debris responsibly for it to work. Currently, other agencies removing space objects may encourage private operators to launch more satellites.
Instead, a suggestion is to implement an orbital-use fee instead of a launch fee. A tax on orbiting satellites could encourage private firms to think more responsibly about how and what they launch. Such fees could rise over time to promote short-term usage.
Laying out end-of-life disposal plans
The European Space Agency has recommended that satellites and orbital stages are commanded to re-enter the Earth’s atmosphere within 25 years of their mission completion, providing their deployment orbit altitude is below 2,000km. Committing to such plans cuts down on the amount of new space debris created through exploration, even if it doesn’t remove what’s already there.
This requires a process known as passivation to be implemented. During passivation, all latent energy reservoirs for a satellite or similar are depleted to reduce the risk of a post-mission explosion. Effectively, such systems need to be designed through a concept known as “design for demise” so they don’t become a threat.
Natural decay is one of the weaker solutions but a plausible one. It relies on objects being dragged into the Earth’s atmosphere with friction and compression, leading them to disintegrate. It’s the cheapest plan, but it’s one that, much like waiting for plastic items to decompose at home, can take hundreds or even thousands of years.
Can space junk be solved?
All the methods above have similar issues and pitfalls. Notably, there are significant legal ramifications to all types of space debris removal. Even if a former satellite is now considered space junk, it remains the property of the country that put it in space. That means that international law can make it difficult or impossible for other countries to remove it.
That’s why countries must cooperate and work with private companies to ensure a positive response. Unity is vital as countries will struggle without sharing space debris data or working together to identify and remove space objects that are now unnecessary.
The cost issue is also a continuing problem, with debates raging over whether new satellites must be issued to remove previous ones or whether there are cheaper methods. While the space debris problem is well-documented, such space junk appears to be less of a priority than exploration and progress within the solar system.
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