Deorbiting and Utilization: Pathways to Sustainable Space and New Markets

Space debris poses a significant threat to the sustainability of orbital operations. This article provides an overview of deorbiting technologies and the emerging concept of space debris utilization.

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The Growing Challenge of Space Debris

Space debris encompasses defunct satellites, spent rocket stages, and fragments from collisions or explosions. As of 2024, the European Space Agency (ESA) estimates that there are over 36,000 cataloged objects larger than 10 cm, and over 1 million objects between 1 cm and 10 cm in low Earth orbit (LEO). These objects can travel at velocities exceeding 28,000 km/h (which makes the maximal possible collision velocity equal to 56,000 km/h), making even small fragments potentially catastrophic, especially in LEO, where speeds are higher, objects are more numerous, and their trajectories intersect due to different inclinations.

NASA’s Orbital Debris Program reports an annual increase in collision probability due to debris accumulation. For example, within one year (2022 to 2023) SpaceX doubled the reported avoidance maneuvers. A single collision could result in losses exceeding $100 million, considering spacecraft damage and operational disruptions. Anti-satellite (ASAT) tests by the USA, Russia, India, and China intensified debris concerns, prompting calls for stronger international regulations.

Of course, the best way to eliminate space debris is to avoid it: satellites must be de-orbited at the end of life, using onboard thrusters or one of the passive deorbiting methods listed below. (Read our article on the low thrust engines here). But what if a satellite is too small to have its own propulsion system, or its propulsor is no longer operational? And what if one needs to de-orbit a piece of junk detached from a larger body? Let’s investigate what can be done in these cases. (Also read our intro to the space debris topic, an overview of space traffic management, and takeaways from a space debris conference).

Deorbiting Technologies

Active Debris Removal (ADR)

Active Debris Removal involves capturing and deorbiting debris using dedicated spacecraft. Prominent methods include:

• Robotic arms: Companies like ClearSpace (Series A, total funding: $33.3M) are developing robotic missions to grapple and remove defunct satellites. Pros: High precision, suitable for large debris. Cons: High cost and complexity.

• Harpoons and nets: ESA’s RemoveDEBRIS project successfully demonstrated harpoon and net technologies. Companies like Altius Space Machines (early-stage funding: $250k, acquired by Voyager Space) are innovating in compact capture mechanisms to aid post-mission disposal. Pros: Simple mechanisms, effective for medium-sized debris. Cons: Limited to certain debris shapes and sizes.

• Laser ablation: Ground- or space-based lasers target debris to evaporate material from its surface - a process called ablation, creating thrust that changes the debris' trajectory, pushing it into a decaying orbit. NASA's ORION project (conceptual stage); Australian National University has been researching ground-based laser systems. Pros: Non-contact method, suitable for small debris at various altitudes. Cons: High energy requirement, potential geopolitical concerns about dual-use technologies.

Passive Deorbiting Mechanisms

Passive systems aim to accelerate the natural orbital decay of satellites:

• Drag sails: Deorbit systems like those developed by Vestigo Aerospace (Seed/SBIR grant, total funding: $443k) use drag sails to increase atmospheric drag: the larger the size of the satellite is, the higher the drag. Pros: Low cost, simple implementation. Cons: Ineffective in higher orbits.

• Electrodynamic tethers: Japan’s JAXA and Astroscale (Latest stage: Series G, total funding: $383M, public since June 2024, TYO: 186A) are exploring tethers to generate drag using Earth’s magnetic field - just the same way, as magnets are used in electric cars to generate force on current-currying wires in your electric car. Pros: Effective for lowering orbits in LEO. Cons: Ineffective in higher orbits and GEO, as the Earth’s magnetic field is weaker there.

Future Trends and Preferred Technologies

For LEO, passive drag mechanisms are cost-effective for smaller satellites, while ADR methods such as robotic arms are better suited for large defunct satellites. Little fragments could be more effectively deorbited using methods like laser ablation. For MEO (above 2,000 km above the Earth) and GEO, ADR technologies like robotic arms are essential due to slower orbital decay rates and the need for precision.

Graveyard orbits are also a proven solution for GEO and MEO. Although it can not be called a deorbiting technology: it is rather the answer to the question of where to deorbit. A graveyard orbit is a stable, high-altitude orbit where defunct satellites are moved after their operational lives have ended. By removing defunct satellites from busy operational zones (e.g., GEO), they prevent potential collisions. A good example is the orbit ~300 km above GEO. Pros: Requires less fuel than deorbiting satellites into Earth's atmosphere, ensures that valuable orbital slots in operational belts remain available for new missions, and objects in graveyard orbits are not subject to significant orbital decay, reducing the need for long-term monitoring. Cons: Unlike debris in LEO that may naturally decay and burn up, objects in graveyard orbits do not re-enter Earth’s atmosphere. While they reduce immediate risk, graveyard orbits contribute to long-term space debris, as objects in these orbits remain indefinitely. Only viable for satellites with sufficient fuel reserves at the end of life.

Space Debris Utilisation

The utilization of space debris involves repurposing or recycling debris for in-orbit applications. Technologies are being developed to extract and process materials from defunct satellites and rocket stages.

NanoRacks (acquired by Voyager Space) is exploring the recycling of debris materials for 3D printing in space. Concepts under exploration by startup Cislunar Industries (seed funding: $5M) include leveraging metallic parts of the debris to recover it into a standardized metal feedstock.

Space debris management is no longer optional; it is imperative for ensuring the sustainability of space activities. Policymakers must enforce stringent debris mitigation standards while fostering public-private partnerships to accelerate technological development. For investors, deorbiting and utilization represent high-growth opportunities with significant societal impact. Engineers must focus on scalable, cost-effective solutions to address the growing debris challenge. Success in this field depends on coordinated efforts among stakeholders, from regulators to technology developers.

We hope that thanks to companies building the solutions and policymakers, astronauts will never face tragic events with space debris which was demonstrated in the movie Gravity (2013). And what do you think about the topic? Please, shoot us an email via hello@spaceambition.org.