As humanity’s presence in space continues to expand, so does the problem of space debris. Thousands of defunct satellites, spent rocket stages, and other discarded objects orbiting Earth pose a significant hazard to both active spacecraft and future space missions. To combat this growing threat, scientists and engineers have developed innovative space debris cleaning technologies. However, these technologies come with a dual-use potential that extends beyond debris removal—they can also be utilized to disable adversary satellites. In this article, we will explore the dual-use nature of space debris cleaning technologies and the implications for space security.
Over the past six decades of space exploration, our activities in the cosmos have left behind a troubling legacy—space debris. This space junk, comprised of defunct satellites, discarded rocket stages, and other fragments, is accumulating at an alarming rate. Recent estimates reveal the scale of the issue: there are over 22,000 objects larger than 10 cm, a staggering 600,000 objects larger than 1 cm, and a mind-boggling 500 million objects larger than 1 mm orbiting Earth. This cosmic clutter poses a significant threat to both active spacecraft and future missions. Furthermore, with companies like SpaceX and OneWeb planning to launch tens of thousands of new satellites in the coming years, the issue of space debris is only set to intensify, endangering astronauts and critical space missions.
The Space Debris Conundrum
Before delving into the dual-use aspect, it’s crucial to understand the severity of the space debris problem. Space debris, ranging from tiny paint flecks to large defunct satellites, travels at high speeds in Earth’s orbit. Even a small collision with a piece of debris can inflict catastrophic damage on operational satellites or spacecraft.
Any debris objects can cause harm to an operational spacecraft, where a collision with a 10-cm object could entail catastrophic fragmentation, a 1-cm object will most likely disable a spacecraft and penetrate the satellite shields, and a 1-mm object could destroy sub-systems on board a spacecraft.
Space Debris in Action: Real-World Threats
The dangers posed by space debris are not theoretical; they are tangible and have already resulted in critical situations. In November 2021, the International Space Station (ISS) had to perform a maneuver to evade a piece of debris created by a Chinese antisatellite weapon test back in 2007. This incident highlighted the real and immediate risks faced by astronauts in space.
One particularly concerning case was the destruction of the Russian Cosmos-1408 satellite in November 2021. This event, resulting from a direct-ascent anti-satellite missile test, generated over 1,500 pieces of trackable orbital debris and is expected to produce hundreds of thousands of smaller debris fragments. Such debris proliferation only adds to the space junk problem.
Furthermore, a Chinese satellite had a close call in January 2020 with debris created by Russia’s destructive anti-satellite test, illustrating the global reach of the space debris issue. A single collision with space debris can have catastrophic consequences; a 10-cm object can cause a catastrophic fragmentation, a 1-cm object can disable a spacecraft and penetrate satellite shields, and a 1-mm object can destroy onboard sub-systems.
Space Debris Mitigation: Innovations and Challenges
To address the space debris challenge, space agencies and organizations are actively developing and implementing mitigation strategies. Active debris removal missions are being planned to capture and remove large defunct satellites and rocket stages from orbit. Passive mitigation techniques involve designing spacecraft and satellites to limit the generation of debris upon decommissioning. Responsible space operations entail deorbiting satellites at the end of their missions to ensure their safe re-entry into Earth’s atmosphere.
Passive Mitigation Techniques: Preventing Debris Generation
While active debris removal focuses on cleaning up existing space debris, passive mitigation techniques aim to prevent the generation of new debris in the first place. These strategies involve designing spacecraft and satellites with features and practices that limit their contribution to the growing space debris problem, especially upon decommissioning or at the end of their operational lifespan. Here are some key aspects of passive mitigation techniques:
Collision Avoidance: Space agencies and organizations also employ collision avoidance measures to prevent in-orbit collisions between active satellites and space debris. These measures include monitoring the positions of operational satellites and providing collision avoidance maneuvers when necessary to keep active satellites safe.
Satellite Design: Passive mitigation begins at the design phase of satellites and spacecraft. Engineers and space agencies focus on creating spacecraft that are less likely to fragment upon decommissioning or collision. This involves designing structures that are resilient to impacts and ensuring that critical components, like fuel tanks and batteries, are positioned to minimize the risk of explosions or fragmentation.
To safeguard against the threat posed by small debris in space, the International Space Station (ISS) has employed a robust defense mechanism for years. Multiple layers of Nextel and Kevlar body armor fabric have been meticulously wrapped around the station, forming a protective cocoon against the hazards of meteorites and other celestial debris.
In a significant development, Russia is set to enhance the safety of the ISS even further. The Science-Power and Prichal Nodal modules, slated for delivery and attachment to the ISS in 2021 and 2022 respectively, will play pivotal roles in the creation of Russia’s forthcoming space station. These state-of-the-art scientific and energy modules, which are destined for the Russian segment of the ISS, will incorporate cutting-edge, domestically engineered body armor fabric-based anti-meteorite protection.
As detailed in Space Engineering & Technology, the official journal of Russia’s Energia rocket and space corporation, the materials used in the buffer shield’s construction, namely basalt and body armor fabrics, exhibit properties comparable to the Nextel and Kevlar fabrics employed in NASA’s module shielding. This innovative approach ensures the continued safety and resilience of the ISS and represents a significant stride in space technology.
Controlled Deorbiting: One of the fundamental principles of passive debris mitigation is to ensure that satellites and spacecraft are equipped with propulsion systems or mechanisms that allow them to be deliberately deorbited at the end of their missions. This controlled deorbiting involves firing thrusters to lower the satellite’s altitude gradually until it reenters Earth’s atmosphere, where it burns up entirely. This practice prevents defunct satellites from becoming long-term space debris.
Electrodynamic Tethers: Riding the Magnetic Waves to Deorbit
Electrodynamic tethers are a fascinating and innovative solution for controlled deorbiting of satellites and space debris. These long, conductive wires are deployed in space and interact with Earth’s magnetic field to generate thrust. By capitalizing on this electrodynamic interaction, satellites or debris attached to tethers can effectively lower their orbits over time. This controlled descent ultimately leads to their safe reentry into Earth’s atmosphere, where they burn up upon arrival. Electrodynamic tethers represent a sustainable and efficient means of addressing the space debris issue, offering a promising avenue for cleaning up the increasingly crowded space environment while minimizing the risk of further collisions and damage to operational satellites.
One notable technology developed by Bruce Davis and his team at Roccor involves attaching a sheet of metal to a satellite before launch. After a designated period in space, a timer deploys the metal sheet, which then helps drag down space debris into Earth’s atmosphere, where it vaporizes upon reentry.
Engineers from the Naval Research Laboratory launched the TEPCE (Tether Electrodynamic Propulsion CubeSat Experiment) aboard a SpaceX Falcon Heavy rocket in June 2019. TEPCE utilizes a kilometer-long tether positioned in Earth’s ionosphere to generate electric currents through interactions with charged particles, specifically free electrons and positive ions. This electric current, driven by the Lorentz force, can be harnessed for either propulsion or drag. When the current flows in one direction, it creates drag, slowing the satellite and reducing its orbital altitude. Conversely, reversing the current direction produces propulsion, enabling more complex orbital maneuvers without requiring additional fuel. These technological advancements represent a significant step in the field of space debris removal and sustainable space operations.
Propellant Residuals Management: Satellites often carry residual propellants at the end of their missions. Passive mitigation strategies emphasize the safe depletion or venting of these propellants to reduce the risk of explosions in orbit, which can create additional debris. Proper management of propulsion systems ensures that no hazardous materials remain in space.
By incorporating these passive mitigation techniques into the design and operation of spacecraft, the space community aims to minimize the generation of space debris and reduce the long-term impact on the space environment. These strategies not only protect operational satellites but also contribute to the sustainability of space activities and the safety of future space missions.
Active Debris Removal: Clearing the Cosmic Clutter
One of the most proactive strategies for mitigating space debris involves active debris removal missions. These missions are akin to cosmic cleanup operations, where specialized spacecraft are designed and launched with the primary mission of capturing and removing large defunct satellites, rocket stages, and other sizable space junk from Earth’s orbit.
Active debris removal missions typically employ a variety of capture mechanisms, including robotic arms, nets, harpoons, or even sophisticated grappling devices. Giant nets and magnets have also been considered to sweep up and attract space debris out of orbit. Active de-orbiting techniques, employing robotic Orbital Transfer Vehicles, aim to remove end-of-life satellites from orbit. However, the economic viability of these methods remains a challenge. Another involves collecting debris in a foamy ball of aerogel.
The process starts with identifying the target space debris, which can be a challenging task given the vastness of space and the multitude of objects in orbit. Once the target is identified, the removal spacecraft is launched and carefully navigated to rendezvous with the debris.
Upon reaching the target, the spacecraft deploys its capture mechanism, whether it’s a net designed to envelop the debris, a harpoon meant to pierce and secure it, or a robotic arm for precise manipulation. Once the capture is successful, the spacecraft may then deorbit the captured debris or guide it toward a trajectory that leads to its safe reentry into Earth’s atmosphere. During reentry, the captured debris burns up, effectively eliminating it as a threat to active satellites and future space missions.
Active debris removal missions are complex and costly endeavors, but they play a crucial role in reducing the risk posed by large and potentially hazardous space debris. These missions not only help make space a safer place for operational satellites but also contribute to the long-term sustainability of space activities.
Space Harpoons and Nets: Cleaning Up the Cosmic Junkyard
Space harpoons and nets represent innovative methods for tackling the ever-growing problem of space debris. These devices work by capturing and securing defunct satellites, spent rocket stages, and other discarded objects orbiting our planet. Once ensnared, the debris is effectively rendered harmless. The methods employed in these technologies vary: harpoons can pierce through defunct satellites, securing them for eventual disposal, while nets envelop and trap space debris, preventing it from posing further risks. More ambitiously, some designs aim to guide captured debris towards reentry into Earth’s atmosphere, where it will incinerate upon reentry. These techniques offer a practical and environmentally responsible approach to cleaning up the cosmic junkyard that endangers active satellites and future space missions.
Laser-Based Tracking and Deorbiting: Precision from the Ground to the Cosmos
Laser-based tracking and deorbiting technologies represent a significant advancement in our quest to combat space debris. Ground-based lasers equipped with sophisticated tracking systems can monitor the trajectories of space debris with remarkable precision. However, their capabilities extend beyond tracking. In certain scenarios, lasers can be used for laser ablation, a process where a laser beam is focused on a target in space. This can be employed to gradually alter an object’s trajectory, nudging it towards a controlled deorbit. The potential of laser-based technology lies in its ability to target and mitigate space debris hazards with unparalleled accuracy, reducing the risk of collisions and space clutter.
Laser technology for space debris removal has garnered significant attention from space agencies worldwide. In 2011, NASA’s Ames Research Center proposed the use of a 5KW laser to target space debris, slowing its speed and causing it to re-enter Earth’s atmosphere and burn up. NASA estimated that such a laser could potentially eliminate up to ten pieces of space junk daily, offering a promising solution for a debris-free future.
Chinese scientists have also embraced the concept of space-based lasers for debris removal. A study led by Quan Wen from China’s Air Force Engineering University, in collaboration with the Institute of China Electronic Equipment System Engineering Company, explored the idea of fragmenting space debris into smaller, less hazardous pieces using space-based lasers. This approach aims to slow down space debris sufficiently for it to safely burn up upon re-entry into Earth’s atmosphere.
However, it’s worth noting that lasers in space have dual-use potential, with applications in both civilian and military domains. Concerns have been raised about China’s development of lasers for anti-satellite purposes, including reports of laser weapons targeting American spy satellites to disable their sensitive surveillance equipment. This underscores the need for international cooperation and transparency in space activities involving laser technology.
The study conducted numerical simulations to assess the effectiveness of an orbital station equipped with a high-powered pulsed laser for debris removal. It concluded that the station’s inclination and right ascension of ascending node (RAAN) should match that of the debris for optimal removal efficiency, providing a theoretical basis for deploying space-based laser stations.
While most research has concentrated on ground-based laser systems, space-based laser technology offers greater flexibility in addressing the space debris problem. It operates in two modes: direct ablation mode for tiny debris particles, where laser energy burns down the debris, and ablation back-jet mode for larger debris particles, using laser energy to alter their orbits. This approach leverages the drastic aerodynamic heating effect to burn up debris as it passes through the upper atmosphere.
In summary, laser-based technologies for space debris removal hold promise in addressing the growing challenge of orbital debris, but they also raise concerns about their potential military applications. International collaboration and responsible use of this technology are crucial to ensure the long-term sustainability of space activities.
The Dual-Use Dilemma
While these space debris cleaning technologies hold promise for making space safer, they also have dual-use potential, which raises concerns about their application in military operations. Here are a few considerations:
1. Anti-Satellite (ASAT) Capabilities: The same techniques used to capture or deorbit space debris can be employed to disable adversary satellites. A harpoon or net designed for debris removal could be adapted to capture and disable operational satellites. Sspace-based lasers for debris removal can be employed as Anti-Satellite Laser Directed Energy Weapons (ASAT Laser DEW), that utilize laser beams to transmit energy from the weapon to the target satellite. These weapons offer several advantages in offensive counter-space operations against orbital assets. Firstly, they operate at the speed of light, ensuring near-instantaneous results, which minimizes the effectiveness of enemy defenses. Secondly, soft kill and non-lethal satellite attacks conducted with laser DEWs allow for plausible deniability. Laser weapons can sustain continuous operation, limited only by available power, and the desired outcomes can range from temporary disruption and degradation to permanent damage and destruction.
2. Denying Access to Space: ASAT capabilities developed from debris removal technologies could potentially be used to deny access to space or disrupt satellite-based communication, navigation, and reconnaissance systems.
3. Escalation Risks: The deployment of dual-use space debris cleaning technologies for military purposes could escalate conflicts in space and contribute to the weaponization of the space domain.
China’s Approach: Scavenger Satellites and Laser Solutions
China has actively pursued solutions to the space debris problem. They launched the Shijian-21 satellite in 2021, designed to test space debris mitigation technologies. Chinese scientists have also developed scavenger satellites, capable of grabbing and deorbiting uncooperative space debris. These satellites utilize sensors and robotic arms to safely remove debris from orbit, reducing the space clutter.
Shijian-21 is part of a series of small satellites, some weighing less than 10 kilograms, designed to capture uncooperative targets like defunct spacecraft in near-Earth orbit. Equipped with a triple-eye sensor system, these satellites can assess the target’s shape, relative speed, and random rotation. When the target comes within 20 centimeters, a single-axis robotic arm on the scavenger satellite latches onto it.
Following capture, the scavenger satellite activates thrusters to redirect the debris, causing it to re-enter Earth’s atmosphere and burn up. China has launched approximately ten experimental scavenger satellites over the past decade, but it is not the only nation pursuing this technology. The European Space Agency has also launched satellites to explore methods like net-based debris capture, and the U.S. military is reportedly developing technology that leverages drifting debris as a tactical hideout for smaller satellites in potential space warfare scenarios.
Notably, the interest in this satellite extends beyond its declared mission, as space debris mitigation technologies have “dual-use” applications, potentially serving both civilian and military purposes. Chinese scientists have been testing this technology since 2008, as revealed in declassified documents. These small probes have the capability to attach themselves to targets such as defunct spacecraft in near-Earth orbit, offering potential military applications where they can remain attached to evade tracking.
China has also been researching laser-based solutions, both for space debris removal and potential anti-satellite applications. The concept involves using high-powered lasers to slow down debris, causing it to enter Earth’s atmosphere and burn up. This technology, though promising for debris mitigation, also raises concerns about its potential dual-use nature for anti-satellite purposes.
China has invested in a dedicated program for developing high-power solid-state lasers and adaptive optics to maintain laser quality over large distances, making them viable for use against satellites. In 2013, Raycus achieved a significant milestone by developing China’s first 10 kW fiber laser, making China the second country in the world to master this technology. In subsequent years, Raycus unveiled a 20 kW fiber laser, which was expected to enter mass production by 2018, further advancing China’s capabilities in directed energy weapons.
In a similar vein, NASA and other space agencies have explored the use of lasers for debris removal, with the ability to migrate space junk toward Earth’s atmosphere for safe disposal.
Russian Space Systems (RSS)
Russian Space Systems (RSS) has developed an innovative space junk recycling system designed to capture decommissioned satellites in Earth’s orbit and transform them into fuel, as reported by the media. This space debris disposal system, weighing approximately 2.5 tonnes, is capable of capturing “decommissioned small satellites in low orbits (ranging from 500 to 700 km),” according to Marina Barkova, the project developer and RSS Research Engineer, in an interview with TASS news agency in March 2019.
The recycling system comprises a trap with a net in the shape of a cupola and a cone, along with a processing device. When a satellite is captured by the trap, it goes through a processing stage involving a grinder and a special mill. Subsequently, the satellite is mixed with oxygen and hydrogen, transforming it into fuel. This fuel is then utilized in the system’s engines for maneuvers and travel to the next satellite that has reached the end of its operational life. To power its onboard computer and robotized control devices, the space chopper relies on solar panels.
Initially, the estimated cost of this innovative “satellite hunter” is around $117 million. It is anticipated to be launched to an altitude of 400 km without the need for a booster to save on costs. However, its target orbit will range between 800 and 1,500 km. According to data from NASA, there are currently over 2,200 active satellites and more than 5,000 decommissioned satellites in orbit, along with over 14,000 fragments of space debris. Overall, nearly 20,000 objects have been registered in Earth’s orbit to date. The recycling system will locate space junk by utilizing data from Russian and international catalogs of space objects, as stated in the report.
Mitigating the Risks
Addressing the dual-use nature of space debris cleaning technologies requires a multifaceted approach:
1. International Collaboration: Nations must engage in diplomatic efforts to prevent the weaponization of space and promote peaceful cooperation in orbit.
2. Transparency and Confidence-Building Measures: Transparency regarding space activities and capabilities can help reduce mistrust and the temptation to develop dual-use technologies for military purposes.
3. Norms and Agreements: The establishment of international norms and agreements governing space activities, particularly the use of debris removal technologies, can contribute to a more secure and stable space environment.
The growing problem of space debris is a challenge that demands innovative solutions and international cooperation. As our activities in space continue to expand, so does the urgency of addressing this issue. While promising technologies for space debris removal are on the horizon, the potential dual-use of some of these technologies for military purposes underscores the need for responsible development and international norms.
To ensure the peaceful and responsible use of these technologies, international cooperation, transparency, and the development of norms and agreements are essential. As we venture further into the cosmos, it is crucial to strike a balance between advancing space exploration and maintaining space security. Continued research, cooperation, and responsible use of emerging technologies are the keys to unlocking a debris-free future in space