Satellites powered by solid metal could one day use space junk for fuel

CNN

18-03-2025

Space is getting crowded — humans have now placed over 20,000 satellites into orbit since the start of the space age, and there are plans to launch thousands more over the next few years.
Some of those satellites have already burned up in the atmosphere or fallen back to Earth, often into the ocean, but more than 13,000 are still up there. About a fifth are inactive, simply orbiting as as space junk. Over the last couple of decades, hundreds of these dead satellites have collided to create millions of pieces of shrapnel.
That creates a constant risk of collision for active satellites and for the International Space Station — a problem so severe that several surveillance networks across the globe closely watch thousands of larger objects, to move spacecraft out of the way when needed.
The increasing threat from space debris calls for both higher maneuverability in orbit and a reduction of the amount of junk. British startup Magdrive claims it can help with both, via a new propulsion system for spacecraft that will launch into space for the first time later this year and will be fueled by solid metal.
'We wanted to build something that really moved the needle for humanity in the space industry, and let us climb the rungs of the ladder to becoming a spacefaring civilization,' says Mark Stokes, who co-founded Magdrive in 2019. He claims that using a solid metal propulsion system can make satellites 10 times as maneuverable, while also reducing the mass devoted to propulsion by 10 times.
Magdrive is working on three versions of its space thrusters, and because they run on solid metal, they might one day even be powered by space junk collected directly in orbit, turning it from threat to fuel source.
Satellites need propulsion systems for a number of reasons, including to change to a different orbit, to compensate for atmospheric drag which would destabilize the orbit they are on, to avoid debris, and eventually to de-orbit themselves.
The majority of satellite propulsion systems are currently either chemical or electrical, but according to Stokes, both have downsides: 'Chemical propulsion has very high thrust, but its efficiency — or its miles per gallon, if you like — is very poor,' he says. 'On the other hand, electric propulsion systems these days have the complete opposite characteristics. They have very low thrust, but excellent efficiency, excellent miles per gallon.'
Humanity's biggest ambitions for the space economy, including asteroid mining, large satellite constellations and building space stations in orbit are, Stokes says, out of reach for now because these propulsion systems require a trade-off between power and efficiency — a decision that has to be made even before the satellite is launched.
'We're building the first system of its kind that has the best of both worlds,' he adds. 'It is electric propulsion, but it has a magnitude improvement in thrust, with a magnitude reduction in volume and mass.'
The first incarnation of the Magdrive system — called Warlock — is set to launch into orbit in June 2025. It works by creating power using onboard solar panels, just like current electric propulsion systems. But whereas current electric systems use the power to ionize, or detonate, a pressurized gas – often a toxic chemical called hydrazine – Magdrive uses it to ionize solid metal.
'That has a lot of advantages, as you can imagine,' Stokes says. Metal is very dense, which means it takes up less onboard space than a tank containing pressurized gas. That, he adds, would make life easier for satellite manufacturers, who consider pressurized tanks 'a headache' as they are difficult to work with and can cause explosions if ruptured, while the metal is inert and doesn't suffer any degradation over time. For now, Magdrive uses copper, chosen because it's relatively cheap and widely available, although any metal would do the job, according to Stokes.
Once detonated, the metal is turned into extremely hot and dense plasma, or electrically charged gas. 'What you get is this highly energetic copper plasma leaving the back of the thruster,' Stokes continues, which moves the thruster in the opposite direction.
For now, the system is not refuelable. In the more distant future, however, Stokes believes the system could obtain its fuel from existing space junk, by harvesting dead satellites for metal to use as propellant — although as yet this plan is only hypothetical. 'The benefit of this is that we'll be able to close the loop on the new space age economy by using resources which are already there,' says Stokes.
That would make Magdrive, Stokes adds, the only propulsion system that doesn't have to take along its fuel every single time. 'Right now, each satellite needs to bring its propellant from Earth, and that's like building a new train every time you leave the station,' he says.
The company is aiming for its first commercial deployment by next year, and targeting clients with a wide range of needs: 'We're building a standardized piece of hardware which can fit on board any satellite — so pretty much anyone in the entire space industry,' Stokes explains. 'This includes a variety of different applications, from Earth observation to satellite servicing to communications,' he says, and can be used on satellites weighing anything from 10 kilograms (22 pounds) up to 400 kilograms (880 pounds).
According to MinKwan Kim, an associate professor in astronautics at the University of Southampton, in the UK, who has been involved in research projects and collaborations with Magdrive, using solid metal fuel offers simplified storage and handling compared to gas or liquid propellants. It allows for a simple design that is particularly suited for mass production, creating a viable path to future mega-constellations that require large-scale satellite manufacturing.
'However, metal propellant usage presents a significant challenge: surface contamination, particularly for solar panels and optical systems,' he adds. Since metal plasma is produced during operation, it can easily deposit on surfaces, potentially affecting the overall performance of the spacecraft.
Stokes says that in the Magdrive system, the metal fuel is consumed completely during the reaction, but then recombines into what he calls 'dispersed inert material,' which he says carries only a small risk of contaminating nearby surfaces due to the exit velocity of the particles — 'nothing to be overly concerned about getting on other components or on other satellites.'
Ensuring reliable and consistent thrust generation, Kim adds, poses another challenge, particularly for precise maneuvering. The heating and cooling cycles the metal fuel goes through during thrust generation can alter its atomic crystal structure, affecting its performance as a propellant. To maintain uniform thrust output, a precise monitoring and control system would be required, adding complexity to the system.
As for using space debris as a fuel, Kim says it's theoretically possible, but there are significant technical and regulatory challenges. The first is that while space junk may seem like a free resource, the UN Outer Space Treaty (OST) states that ownership of objects launched into space remains unchanged, even if they become debris. This means permission from the original owner is required before recycling a satellite. Additionally, some satellites contain sensitive data or proprietary technology, making owners reluctant to grant access. Finally, the launching country bears responsibility for any incidents caused by a recycled satellite, adding another layer of legal complexity.
Then there are the practical issues, says Kim: 'Decommissioned satellites are uncontrollable and often tumbling, making retrieval extremely difficult. Capturing and securing them requires complex maneuvering, a technology still in its infancy,' he says. Kim added that these satellites are not made of just metal but also materials such as silicon and polymers, which is an issue because the quality and purity of metal propellant directly impacts thrust performance, so without tight control over the collected metal's composition, achieving reliable and predictable thrust would be difficult.
'As a result, while space junk-derived metal might be suitable for non-precision maneuvers such as deorbiting, it is unlikely to be viable for high-precision propulsion.'