Space pollution: to clean where no one has cleaned before

Space has long been the preserve of government agencies and the big names of the aerospace industry. However, for the past ten years or so, new commercial players have been seeking to stake their claim to the heavens, like Elon Musk and his famous SpaceX project. This phenomenon of opening space up to private actors, combined with the technological developments of the last 20 years (nanosatellites, reusable rockets) has profoundly transformed the space sector. And, today, "new space" represents both a considerable advance in the exploration of space but also a threat to its preservation. 

The sky taken by storm

The multiplication of satellite launches¹ increases the risk of collision with aircraft or other debris that generates ever more debris (risking a self-sustaining chain reaction in debris generation known as the Kessler syndrome). This is why such space debris is constantly monitored, particularly by the National Centre for Space Studies in Toulouse (CNES) and by the European Union, which contributes to the protection of more than 550 satellites worldwide through a system² that tracks objects in orbit.

The impact on climate pollution of sending communication or geolocation tools into space is also concerning experts. A NASA team studying the trail of a satellite launcher in the stratosphere has observed³ that the pollutants released have the effect of increasing the temperature in the stratosphere and degrading the ozone layer.

Innovating to make a clean sweep

Innovative approaches are under-way to clean up our space backyard. The ESA project, Active Debris Removal (ADR), aims to clear space of its largest pieces of debris. In 2019, the European Space Agency commissioned the Swiss start-up ClearSpace to build a demonstrator to recover a stage of the Vega launcher that has been stuck in low Earth orbit since 2013.

Two years later, the Japanese start-up Astroscale⁴ tested a "garbage collector satellite" equipped with powerful magnets, capable of attaching to debris and redirecting it towards Earth so it disintegrates upon entering the atmosphere. In 2023, the American company TransAstra⁵ received funding of $850,000 from NASA to manufacture capture bags capable of trapping miniature cube satellites at the International Space Station.

As for the Japanese group Orbital, they are studying the possibilities of installing a laser on a small cleaner satellite to target space debris and thus slow it down. The aim would be to prepare the debris for capture, most probably using Astroscale's debris-removal satellite.

According to Christophe Bonnal, expert researcher in space debris⁶  at CNES, "If we managed to remove about ten (large pieces of debris) per year, the growth [of satellites] would cease to be exponential, and over twenty years, we would manage to stabilise the general situation".

Towards more sustainable practices

Engineers are also working on the eco-responsible design of artificial objects sent into space, starting with the satellites themselves. In 2024, the world's first wooden model, named LignoSat7 and developed by scientists from Kyoto University and Sumitomo Forestry company, took off aboard a SpaceX rocket. The device itself is biodegradable: once it reaches the end of its life, it should re-enter the atmosphere and burn up completely, without leaving toxic residues behind.

Rockets are also being extensively studied, particularly given the emergence of space tourism. In addition to partially becoming waste once obsolete, when it comes to satellite launchers, their very launch into space is polluting. According to the British specialist firm Northern Sky Research (NSR), a one-and-a-half-hour suborbital flight of Virgin Galactic's rocket plane emits as much CO2 as a 10-hour transatlantic flight.

To try to address these issues, the French start-up Alpha Impulsion has created a new model of “autophagic” ⁸ rocket, which in other words is one that "eats" itself during its launch into space, limiting space debris. Made from recycled or bio-based polyethylene, the satellite launcher that the company plans to launch in 2028 will use its structure as fuel, thereby reducing its environmental impact by 40%. And the cherry on the cake: such a design would reduce production costs by a factor of five.

As with aircraft, the question of the energy used to power rocket engines also arises. The British start-up Skyrora has developed a prototype rocket powered by Ecosene⁹, a fuel derived from recycled plastic waste. She estimates that, from the production of this fuel to its combustion, the device it would power would generate up to 40% fewer emissions (carbon monoxide and dioxide, soot, sulphur, etc.) than a rocket launched using fossil fuel.

Companies, such as Zero2Infinity, are exploring alternative approaches. The Spanish company is planning to tow a rocket to high altitude using a helium-filled balloon. It is betting on this solution, initially designed to put probes and satellites into orbit, in order to offer a green alternative to space tourism. On board a balloon¹⁰ perched 40 kilometres above the ground, the most daring could treat themselves to thrilling sensations while admiring the curvature of the Earth, the darkness of space or even the stars and planets… all without their journey outside the atmosphere generating excessive greenhouse gas emissions.

While an international legal framework does not yet exist for the regulation of space pollution, the ESA has recently taken a major step forward. In 2024, 12 countries signed the Zero Debris Charter¹¹ which the European Space Agency itself ratified as an international organisation (IGO). It is a unique worldwide effort that commits states to achieving carbon neutrality with respect to space debris by 2030. More than 100 organisations, including international space agencies, satellite manufacturers, start-ups and astronomy companies have confirmed their intention to follow the protocol. "Within 15 years, 100% of the missions we develop will leave no [waste] on the route to space," assures Quentin Verspieren, in charge of debris-free space activities at ESA.