The space junk problem threatening future missions

Today, more than 33,000 tracked objects circle Earth at about 28,000 km/h. These are just the objects that can be seen. At that speed, even a paint flake can cause damage, as seen on the International Space Station. When smaller fragments are included in the count, it rises to tens or hundreds of millions of pieces of debris, according to a report by Accu. 

Of the 33,269 objects currently being tracked in orbit, 12,550 are debris fragments, 2,396 are rocket bodies and 641 are unassigned. That means that nearly 47% of tracked objects are space junk. The count also includes 17,682 satellites, many of which are inactive or uncontrollable. 

The solar influence

Compounding the problem, new research indicates that solar activity and sunspot counts directly influence the rate at which space junk loses altitude. During peak solar cycles, intense radiation expands the thermosphere, creating a denser atmosphere that adds friction and slows down objects in low Earth orbit. 

The new data revealed a sharp increase in orbital decay when sunspot numbers reach about 70% of their cycle peak. The sun’s radiation emission intensity varies on a roughly 11-year cycle. The research indicates that more space debris descends out of orbit as the cycle reaches its peak. 

Understanding these patterns could help engineers better identify ideal launch windows and predict the natural cleansing of orbital paths, which will become even more important as space junk continues to accumulate. 

The Kessler syndrome

In 1978, NASA scientist Donald J. Kessler proposed a phenomenon known as the Kessler syndrome. This is a theoretical scenario where the number of objects in low Earth orbit (LEO) would become so vast that it could make launching space missions impossible. 

The theory is that LEO would reach a critical mass where collisions would inevitably occur. These impacts would create more debris, which would in turn create more collisions. This chain reaction would continue until the entire orbital space is full of debris and impossible to navigate. 

The Kessler syndrome could even stop space telescopes from being effective for observations, as well as satellites used for communications, GPS navigation, the internet and more. 

In 1978, Kessler believed that this reality could come about in 30 to 40 years. Now, some experts believe we are approaching that critical mass. 

Engineering the cleanup

There is currently no large-scale operation in place to remove space debris, but governments and space agencies are investing in removal strategies. A range of technologies are being developed for Active Debris Removal (ADR). 

One possible solution is capture missions, satellites designed to secure, move or deorbit debris. The European Space Agency’s ClearSpace-1 mission plans to use robotic arms to capture a 94 kg object in 2029. 

Electrodynamic tethers (EDTs) could use Earth’s magnetic field to create a drag and gradually pull debris out of orbit without fuel. Similarly, drag sails, large deployable sails that increase atmospheric drag and accelerate orbital decay at end-of-life, have been successfully demonstrated by Rocket Lab and the ESA. 

Another possibility is laser ablation, lasers based on the ground or in space that alter debris trajectories by generating small thrust forces, or magnetic capture, which was demonstrated by Astroscale in 2021. Astroscale’s ELSA-d consisted of two spacecraft: a servicer satellite and a client satellite, launched stacked together. The servicer satellite was developed to remove debris objects from orbit with RPO technologies and a magnetic docking mechanism.