- New ion thruster solution: Scientists have devised a bidirectional ion engine concept that uses its own plasma exhaust to push space debris out of orbit without contact space.com space.com. Two oppositely directed thrusters cancel out each other’s recoil, allowing a cleanup satellite to hold steady while blasting junk with charged particles space.com.
- How it works: The system fires a beam of ionized gas (plasma) at a piece of space junk, gently slowing it down so it falls into Earth’s atmosphere and burns up space.com. A special magnetic field “cusp” design boosts the plasma thrust, achieving ~25 milli-Newtons (mN) of force in lab tests – approaching the ~30 mN needed to deorbit a 1-ton object in ~100 days space.com universetoday.com.
- Safer debris removal: Unlike nets, harpoons or robotic arms that physically grab debris (risky for tumbling objects space.com), this ion beam method never touches the junk. It avoids entanglement or collisions by pushing from a distance, a big advantage since most orbital trash is spinning uncontrollably universetoday.com.
- Innovation and challenges: The thruster runs on inexpensive argon gas instead of costly xenon space.com space.com, but it demands several kilowatts of power for months-long operations space.com universetoday.com. Because it fires two equal plasma jets in opposite directions, it essentially doubles fuel use universetoday.com. So while promising, the technology still needs real-world testing, higher thrust, and solutions for fuel and power demands.
- Debris crisis urgency: Low Earth orbit (LEO) is cluttered with dangerous debris—from spent satellites to stray bolts. Over 14,000 sizable junk pieces crowd LEO space.com (with hundreds of thousands of smaller fragments abc.net.au), all whizzing at bullet-like speeds space.com. This threatens vital satellites and even astronauts on the International Space Station, which must often dodge “space shrapnel” space.com. Experts warn that a major collision could trigger Kessler Syndrome, a cascade of smash-ups making orbit unusable space.com. As one space debris expert put it, “At orbital velocities, even a screw can hit with explosive force… the threat needs to be managed through the active removal of debris” esa.int.
The Ion Engine Exhaust Method: Blasting Debris with Plasma
In this novel concept, a cleanup satellite approaches a piece of orbital debris and fires a stream of plasma (electrically charged gas) from an ion thruster to gradually slow the object’s orbital speed space.com. Slowing an object causes its orbit to decay; eventually it reenters the atmosphere and burns up harmlessly. The key innovation by Kazunori Takahashi of Tohoku University is a bi-directional plasma thruster that solves a fundamental problem: when you shoot an ion beam one way, Newton’s third law pushes your spacecraft the opposite way space.com. Takahashi’s design mounts two ion thrusters back-to-back, firing plasma in opposite directions. The rear thrust balances out the front thrust, so the satellite remains in place while the forward beam strikes the debris space.com.
How an ion thruster works: A gas (typically inert xenon, but Takahashi demonstrated argon for lower cost) is fed into a chamber space.com. Electrons from a cathode ionize the gas, creating plasma – a soup of charged particles. Electromagnetic fields then accelerate the plasma out of a nozzle, producing a gentle but steady thrust space.com. In Takahashi’s device, the magnetic field is shaped with a “cusp” configuration (like those in fusion reactors) to guide plasma out both ends without it sticking to interior walls space.com universetoday.com. “The specific shape of the cusp provides a geometrical separation of the plasma from the wall, reducing the plasma loss,” explains Takahashi space.com. This means more propellant is actually used for thrust rather than wasted, boosting efficiency.
Laboratory tests have been encouraging. By tweaking the magnetic field design, Takahashi’s team achieved a 20% thrust increase at the same power compared to earlier straight-field designs universetoday.com. At about 5 kilowatts of power input, the prototype produced a plasma jet yielding ≈25 mN of thrust universetoday.com. That’s roughly two-and-a-half times stronger than prior tests and on the cusp of the ~30 mN that calculations suggest is needed to deorbit a 1-meter, 1000 kg object in under 100 days space.com universetoday.com. For comparison, Japan’s Hayabusa2 asteroid probe’s ion engine managed ~10 mN using 300–500 W of solar power space.com. Reaching ~30 mN likely requires several kilowatts of power – meaning robust solar arrays or other power sources on the remover spacecraft space.com.
Why go to all this trouble? Because a non-contact “ion beam broom” could safely clean up large, dangerous debris that current methods struggle with. Any direct contact method has to grapple with tumbling objects. By contrast, an ion thruster can station-keep a few meters away and continuously push on the target with plasma streams universetoday.com. Over days and weeks, this gentle nudge compounds into a substantial orbit change. It’s analogous to a cosmic leaf blower nudging debris out of orbit. The approach is especially aimed at big debris (1 ton or more), since those pose the greatest risk of spawning thousands of fragments if they collide with something else space.com. Removing just a few heavy junk objects per year could significantly reduce the odds of an apocalyptic chain-reaction of debris collisions (the Kessler Syndrome) in the future space.com space.com.
That said, the ion-exhaust method is still in early development. So far it’s been tested in vacuum chambers with targets only 30 cm away universetoday.com. In orbit, a removal craft would likely need to work from a few meters distance or more for safety. As the debris slows down, its orbit lowers and its motion relative to the servicer might change, complicating aim universetoday.com. Another challenge is operational duration and fuel: deorbiting a big object could require firing the thrusters for months. Ion thrusters sip propellant compared to chemical rockets, but running dual thrusters 24/7 for 100 days will consume a substantial amount of gas universetoday.com. Because two thrusters fire at once, fuel use is roughly doubled for this method, a trade-off for holding the station steady universetoday.com. Engineers will need to ensure the servicing spacecraft can carry sufficient propellant (argon is cheaper and more plentiful than xenon, easing some cost) space.com space.com. Power is another limiting factor – solar panels or other sources must reliably supply several kilowatts over long periods space.com.
Despite these hurdles, experts are optimistic. “Even with this success, there’s still a lot of work to do before this becomes a fully fleshed out system… [But] any new solution to this potentially catastrophic problem is welcome,” wrote engineer Andy Tomaswick, discussing the demo results universetoday.com universetoday.com. The technology has been published in a peer-reviewed journal (Scientific Reports, Aug 2025) and will likely see further refinement space.com. If future in-space tests pan out, we could one day see dual-blast plasma tugboats methodically sweeping up derelict satellites and spent rocket parts – a continuous gentle shove until each piece of junk falls to a fiery demise in the atmosphere.
How Does It Compare? – Space Junk Removal Methods, Old and New
The ion engine exhaust concept joins a growing list of creative solutions to our orbital debris dilemma. Each approach has its own strengths, challenges, and use cases. Here’s how they stack up:
- Robotic Arms & Claws: One straightforward idea is to grab the junk like a floating game of claw crane. A chaser spacecraft rendezvouses with debris and snatches it using robotic arms or a grappling mechanism. The European Space Agency (ESA) is pioneering this with its upcoming ClearSpace-1 mission. In 2025–26, a Swiss-built “space claw” will launch to capture a 113 kg leftover rocket adapter in orbit, then drag it down into Earth’s atmosphere esa.int esa.int. This will be the first-ever attempt to remove an uncooperative object this way. Robotic capture has the advantage of securing the debris firmly – once you’ve got hold of it, you can steer it to a safe disposal orbit or reentry. However, accomplishing this is extremely tricky. “All orbital captures up to now were of cooperative, controlled targets,” notes former ESA director Jan Wörner. Dead debris tumbling in microgravity is a very challenging catch esa.int. The target might be spinning rapidly or have an awkward shape, forcing complex autonomous guidance and grip techniques esa.int esa.int. A slight miscalculation and the servicer could be struck or sent into an unrecoverable spin itself. Despite the difficulty, progress is being made: NASA and others are investing in on-orbit servicing tech (robotic arms, vision-based navigation, etc.) that doubles for debris removal and satellite refueling esa.int esa.int. The cost is also a factor – ESA’s contract for ClearSpace-1 is €86 million (about $100 M) for a single-object removal esa.int, though future economies of scale and multi-capture missions aim to bring costs down space.com.
- Nets and Harpoons: It sounds like science fiction, but we’ve already tested casting nets and firing harpoons in space. In 2018, the RemoveDEBRIS experimental satellite deployed a net that successfully snared a test object in orbit abc.net.au abc.net.au. The net unfurled and wrapped around a small CubeSat acting as dummy debris, demonstrating one way to ensnare junk. A few months later, in February 2019, RemoveDEBRIS fired a tethered harpoon into another target – essentially spearing a piece of faux debris on a boom abc.net.au. The harpoon struck its mark at 20 m/s, showcasing how we might one day spear and reel in dangerous tumbling objects abc.net.au. Both methods could capture debris without requiring a delicate docking maneuver. They’re relatively simple mechanically (borrowed from fishing or whaling analogies), and a single servicer could carry multiple nets or harpoons to round up several pieces. On the downside, nets and harpoons impart forces on the debris that could break it apart if misjudged. They also face the same tumbling issue – a net or harpoon must hit a moving target just right to avoid glancing off or causing a new fragment cloud. Additionally, a net that wraps around junk still leaves the question of then what? – usually the plan is to tug the captured debris down, which requires a sturdy tether and adds fuel cost. The RemoveDEBRIS harpoon and net were one-off demos at low speeds; scaling up to larger, faster debris will require further engineering. Still, these tests were “truly remarkable” milestones, proving such unconventional tools can work in orbit abc.net.au.
- Lasers “Brooms”: Using lasers to clean up orbital trash might sound like a supervillain scheme, but it’s under serious study. The concept of a laser broom involves firing high-powered laser pulses from the ground (or a satellite) at small debris pieces. Rather than vaporizing the object (which could just create more fragments), the idea is to ablatively nudge it: the laser heats one side of the debris, vaporizing a thin layer and creating a tiny jet of plasma that pushes the object in the opposite direction spie.org. With repeated pulses, this can slow the debris and make it drop into the atmosphere. Another mechanism is simply using photon pressure – a continuous laser beam imparting momentum to nudge orbiting bits. Laser approaches are attractive because nothing has to rendezvous with the debris. Ground-based lasers, in particular, could theoretically target any piece that comes over the horizon. Research by agencies like NASA and organizations in Europe and Australia has found that for debris a few centimeters in size or smaller, lasers could be effective if sufficiently powerful and accurately aimed hou.usra.edu. There are, however, significant challenges: atmospheric distortion, energy requirements, and precision targeting to avoid just scattering the debris. There’s also an international policy wrinkle – a powerful laser system could be mistaken for a weapon, so transparency and cooperation would be needed. As of now, laser debris removal remains in simulation and laboratory stages, though laser tracking of debris is already used to refine orbits of known pieces space.com. The leap to actual laser nudging is likely a few years (if not decades) away, awaiting advancements in adaptive optics and high-energy lasers. If achieved, it could provide a scalable way to sweep up the cloud of millimeter- to centimeter-sized shrapnel that poses a grave threat yet is too small to capture with nets or arms.
- Drag Sails and Passive Deorbiting: Not all solutions involve chasing debris down. What if we make satellites self-destruct (safely) at end-of-life? Enter drag sails – devices that deploy from a defunct satellite to dramatically increase its air drag. Even at 300–800 km up, there’s a thin wispy atmosphere. A deorbit sail is like a parachute (or an “air brake”) for space: it presents a large surface area that causes the satellite to slow faster and drop out of orbit much sooner than it otherwise would esa.int. Several prototypes have flown. In late 2022, a European system called ADEO unfurled a 3.6 m² aluminized sail from a small satellite, successfully accelerating its descent esa.int esa.int. NASA’s earlier NanoSail-D2 test in 2011 deployed a 10 m² polymer sail, showing that even a thin film can expedite reentry. The beauty of drag sails is their simplicity and fail-safe nature: they work passively, requiring no active control once deployed esa.int. They can even help deorbit tumbling, “dead” spacecraft, since increased drag will slow an object regardless of its orientation esa.int. The catch is that a drag sail usually must be built into a satellite before launch (though concepts exist to attach them afterward). They are thus a preventative measure for future debris rather than a way to capture decades-old junk already in orbit. Still, as part of a holistic debris mitigation strategy, drag sails are gaining traction. The International Space Station has tested tether and sail devices, and some satellite operators now include drag tape or sail modules to ensure their satellite disposes of itself within, say, 5–10 years after mission end. This is far better than the “25-year rule” of old guidelines, which left expired satellites lingering as potential hazards for decades. In fact, regulators are tightening rules: the U.S. FCC recently adopted a 5-year deorbit requirement for new satellites, encouraging use of such passive deorbit systems for compliance fastcompany.com. While drag sails won’t address large existing debris, making sure new satellites clean up after themselves is a critical piece of preventing the orbital debris population from growing unchecked.
Each of these methods – and others like tethers (using long cables to generate drag or electro-magnetic forces) or “space tug” concepts – has a role to play. The ion engine exhaust approach is unique in that it’s a non-contact yet active method: it can work from a standoff distance, but still imparts a continuous force to deorbit even big objects. In that sense, it overlaps with laser strategies (non-contact) and ion-beam shepherd concepts that have been theorized before universetoday.com, yet it requires deploying a dedicated spacecraft like contact methods do. The ultimate toolkit for cleaning up space may well include multiple techniques: a mix of robotic grabs for the largest hulks, ion or laser pushers for medium debris, and mandatory drag devices for new satellites, all working in concert to curb the debris menace.
Recent Progress in the War on Space Junk
After years of concept studies, the world is now seeing tangible steps toward active debris removal and improved orbital stewardship:
- First Cleanup Missions: Besides ESA’s ClearSpace-1 mission, which aims to prove out a commercial debris removal service esa.int, private companies like Astroscale have been conducting trials. In 2021 Astroscale’s ELSA-d mission tested a magnetic docking device to capture a client satellite in low orbit. Building on that, Astroscale recently announced a patented “multi-object removal” system – essentially a space tug-and-ferry approach. Under this plan, one carrier spacecraft would rendezvous with multiple large debris objects (like defunct satellites or spent rocket stages) one by one, attach to each, and then transfer each piece to a second vehicle called the “shepherd” for final disposal space.com. The shepherd vehicle would drag the debris down into a controlled reentry, safely burning it up over the ocean. This distributed architecture could dramatically improve efficiency, allowing a single servicer to clear several pieces per mission instead of just one space.com space.com. “Our distributed architecture solves a key challenge in orbital debris removal by enabling the deorbit and reentry of multiple large debris objects sustainably and economically,” Astroscale said of the concept space.com space.com. It underscores a shift toward scalable solutions that reduce cost per debris removed.
- Government and International Initiatives: Governments are recognizing that orbital debris is not just a scientific annoyance but a threat to the space economy and national security. The U.S. Space Force has launched the Orbital Prime program, offering contracts to startups for developing debris-removal technology and planning an in-orbit demonstration of trash pickup by the late 2020s. In Japan, JAXA partnered with Astroscale for a future mission to remove a spent Japanese rocket stage from orbit. The European Union is funding multiple active debris removal projects in addition to ClearSpace-1, and ESA’s director general has called for a “Zero Debris” policy – “if you bring a spacecraft into orbit you have to remove it” esa.int. Policies are tightening too: as mentioned, the U.S. FCC now mandates that any new satellite in LEO must be disposed of within 5 years after its mission ends (a significant tightening from the previous 25-year guideline) fastcompany.com. The UN’s Committee on Peaceful Uses of Outer Space is urging all spacefaring nations to adopt mitigation measures and is facilitating discussions on debris remediation cooperation. Such global rules and norms are crucial; without them, it’s a “tragedy of the commons” scenario nss.org nss.org, where everyone benefits from a cleaner orbit but no single player wants to bear the cost of cleanup.
- Tracking and Collision Avoidance: In parallel with removal efforts, there’s been progress in debris tracking and collision avoidance to manage the current hazard. The U.S. Space Surveillance Network and partners track over 30,000 objects, and new radars (like the Space Fence) and optical telescopes are coming online to detect even smaller bits. Just this year, two European telescopes demonstrated using adaptive optics and lasers to precisely track debris that was previously hard to monitor space.com space.com. Better tracking helps satellite operators dodge debris; however, constant dodging is not sustainable long-term, which circles back to the need for removal. Notably, in August 2023, the very object that ClearSpace-1 planned to remove – a 2013 Vega rocket payload adapter – got hit by another piece of debris, breaking off fragments space.com space.com. This “debris-on-debris” strike, detected by the U.S. Space Force, was a stark reminder that even known large debris can unexpectedly spawn new shrapnel. ESA officials noted that it only strengthens the case for active cleanup missions space.com space.com.
Overall, the tone has shifted from whether we need to remove orbital junk to how fast can we do it. Each success – a net capture, a harpoon strike, a patent on multi-object removal, or a novel ion thruster demo – adds a tool in our arsenal against space pollution.
Public Impact, Feasibility, and the Path Ahead
Why should the public care about space junk? For one, these debris threaten the satellites that provide us everyday services: GPS navigation, weather forecasts, television broadcasts, and global communications. A single collision in the wrong place could knock out an important satellite or generate a debris cloud that endangers many others. In the worst case, a Kessler Syndrome cascade of collisions could render low Earth orbit so perilous that it “could completely block our access to space” space.com. That means no new satellites, no space exploration, and even a risk to astronauts on the International Space Station or future space stations. In short, the stakes extend to global security and the future of space utilization for all humankind.
Cleaning up space is an environmental issue as much as a technical one – it’s about preserving the orbital environment for sustainable use, analogous to cleaning plastic from the ocean or CO₂ from the atmosphere. There’s also a planetary protection aspect: while most debris will burn up on reentry, some larger pieces (like old rocket parts) can survive and hit the ground or ocean, posing hazards to people and nature. Controlled removals ensure debris falls in unpopulated areas or disintegrates fully. Additionally, there’s growing concern over light pollution and radio interference from the swelling number of satellites and debris; removing defunct objects helps mitigate the “megaconstellation” side-effects for astronomers and sky watchers.
That said, who pays for orbital cleanup is a tricky question. Launching a debris removal mission is expensive, and yet the benefits (a safer orbital environment) are shared by all space actors. It’s a classic collective action problem. So far, public funding (through agencies like ESA, NASA, JAXA, etc.) has kick-started the first missions. Going forward, experts suggest a combination of approaches: commercial incentives, government regulation, and international cooperation. Companies might one day offer debris removal as a paid service (especially to satellite operators who need a part of orbit cleaned for their business), or large constellation providers might be required to have end-of-life disposal plans (with hefty fines if they don’t). Internationally, new treaties or agreements may be needed so that one country’s cleanup satellite can legally remove a derelict object launched by another country – currently, under space law, a piece of debris remains the property of the original owner, and removing it without permission could violate sovereignty nss.org space-debris-remediation.com. Solving these legal and diplomatic hurdles will require as much creativity as the engineering solutions.
Encouragingly, awareness of the space debris issue is at an all-time high. High-profile incidents like the 2009 Iridium–Cosmos satellite collision and destructive anti-satellite weapon tests have galvanized the global community. In 2023, the G7 nations even issued a statement on the need for urgent action on space debris. We’re likely to see the first large-scale cleanup missions by the end of this decade, and by the 2030s, if policies align, an routine “orbital garbage collection” service could be a reality.
The ion engine exhaust concept fits into this hopeful outlook as a potential game-changer. If its promise holds, future satellites could sidle up to big pieces of junk and sweep them out of the sky using invisible plasma beams – no grappling hooks or lasers needed. It’s a fundamentally elegant solution: leveraging the physics of ion propulsion (proven on deep-space probes) and turning it into a cosmic broom for our own planetary neighborhood.
Towards a Sustainable Space Environment
Humanity’s footprint in space has long been accumulating in the form of discarded hardware and collision fragments. But now humanity is also coming up with ingenious ways to clean up after itself. Whether it’s a harpoon skewering a piece of space trash, a drag sail unfurling like a flower to deorbit a satellite, or twin ion thrusters quietly blowing a defunct rocket body out of orbit, each innovation brings us a step closer to curbing the space junk problem. Clearing orbital debris will require significant investment and international coordination, no doubt. Yet the cost of inaction – a cluttered, perilous orbit that stifles our space ambitions – would be far higher.
The new ion exhaust method exemplifies the kind of creative thinking needed. It’s leveraging cutting-edge plasma physics to tackle a very modern environmental crisis beyond Earth. As more companies and countries join forces to deploy debris solutions, we can envision a future where orbital highways are regularly patrolled and kept clear, much like we remove trash from shipping lanes or clean up environmental hazards on Earth. In the coming years, keep an eye on demonstrations of this technology and others: the fight to clean up space has truly begun, and it’s poised to make near-Earth space safer for everyone.
Sources: Space.com space.com space.com space.com space.com space.com space.com; Universe Today universetoday.com universetoday.com universetoday.com universetoday.com; ABC News abc.net.au abc.net.au; ESA News esa.int esa.int esa.int; ESA (ADEO drag sail) esa.int esa.int; SPIE (laser concept) spie.org; Space.com (Astroscale patent) space.com space.com; Space.com (ClearSpace target hit) space.com space.com; NSS (COPUOS) nss.org nss.org.
