Space junk, also known as orbital debris, is any human-made object that is no longer in use and remains in orbit around the Earth. Space junk can include defunct satellites, spent rocket stages, fragments from collisions or explosions, and even paint flakes or bolts. According to the European Space Agency (ESA), there are more than 34,000 objects larger than 10 cm, about 900,000 objects between 1 and 10 cm, and more than 128 million objects smaller than 1 cm in orbit.
Space junk poses a serious threat to the safety and sustainability of space activities, as well as the environment and society on Earth. Space junk can travel at speeds of up to 28,000 km/h, which means that even a small piece of debris can cause significant damage or destruction to an operational satellite or spacecraft. This can result in the loss of valuable services such as communication, navigation, weather forecasting, or scientific research. Moreover, space junk can create more debris through collisions or break-ups, creating a cascade effect that could render some orbits unusable in the future. This scenario is known as the Kessler syndrome, named after the NASA scientist who first predicted it in 1978.
Therefore, there is an urgent need to develop and implement effective solutions for space junk cleanup. However, this is not an easy task, as it involves many technical, legal, economic, and political challenges. In this blog post, we will explore some of the current and proposed solutions for space junk removal, as well as some of the challenges and opportunities they present.
Current and Proposed Solutions for Space Junk Removal
There are two main approaches for dealing with space junk: prevention and removal. Prevention aims to reduce the generation of new debris by implementing mitigation measures such as designing satellites to avoid collisions, minimizing the release of fragments during launch or operation, deorbiting or reorbiting satellites at the end of their lifetime, or passivating satellites to eliminate sources of potential explosions. Removal aims to actively eliminate existing debris from orbit by using various technologies such as capture mechanisms, propulsion systems, lasers, or nets.
While prevention is essential to limit the growth of space junk, it is not sufficient to stabilize or reduce the existing population of debris. Therefore, active removal of space junk is necessary to ensure the long-term viability of space activities. However, active removal is also more complex and challenging than prevention, as it requires advanced technologies and capabilities that are not yet fully developed or demonstrated. Here are some examples of current and proposed solutions for space junk removal:
- ELSA-d: ELSA-d (End-of-Life Services by Astroscale-demonstration) is a mission by Astroscale, a Japanese company that aims to provide commercial services for space debris removal. ELSA-d consists of two satellites: a servicer that can capture and deorbit debris using magnets, and a client that simulates a piece of debris for demonstration purposes. The mission was launched in March 2021 and is expected to last for about six months. It will test various scenarios such as rendezvous and docking with a tumbling or non-responsive object, release and recapture of the client satellite, and controlled reentry of both satellites into the atmosphere.
- ClearSpace-1: ClearSpace-1 is a mission by ClearSpace, a Swiss start-up that was selected by ESA for its first active debris removal project. ClearSpace-1 will target Vespa (Vega Secondary Payload Adapter), a 112 kg piece of debris that was left in orbit by a Vega rocket in 2013. The mission will use a four-armed robotic spacecraft that will capture Vespa and drag it into a destructive reentry. The mission is planned to launch in 2025 and will serve as a proof-of-concept for future debris removal missions by ClearSpace.
- e.Deorbit: e.Deorbit is a mission concept by ESA that aims to remove a large ESA-owned satellite from orbit using either a robotic arm or a net. The target satellite could be Envisat, an 8-ton environmental satellite that stopped functioning in 2012 and poses a high collision risk in its orbit. The mission would use an advanced spacecraft that would rendezvous with the target satellite, capture it using either a robotic arm or a net, and deorbit it safely into the ocean. The mission is currently under study and could be launched in the late 2020s.
- RemoveDEBRIS: RemoveDEBRIS was a mission by Surrey Space Centre that tested various technologies for space debris removal between 2018 and 2019. The mission used a microsatellite that deployed four CubeSats to simulate different types of debris. The microsatellite then demonstrated four methods of capturing and deorbiting the CubeSats: a net, a harpoon, a drag sail, and a vision-based navigation system. The mission successfully completed all its objectives and was the first in-orbit demonstration of active debris removal technologies.
- EDDE: EDDE (ElectroDynamic Debris Eliminator) is a concept by Star Technology and Research, a US company that proposes to use electrodynamic tethers to remove multiple pieces of debris from orbit. Electrodynamic tethers are long wires that generate thrust by interacting with the Earth's magnetic field and the ionosphere. EDDE would use a tethered spacecraft that can change its orbit by varying the current in the tether. The spacecraft would rendezvous with a piece of debris, capture it using a net or a clamp, and transfer it to a lower orbit where it would burn up in the atmosphere. The spacecraft would then move to another piece of debris and repeat the process. EDDE could potentially remove hundreds of pieces of debris per year using solar power and without propellant.
Challenges and Opportunities for Space Junk Removal
While the solutions mentioned above show promising potential for space junk removal, they also face many challenges that need to be overcome before they can be widely implemented and accepted. Some of these challenges are:
- Technical challenges: Space junk removal involves complex and risky operations that require high levels of precision, reliability, and autonomy. The technologies for capturing and deorbiting debris need to be able to cope with various factors such as the size, shape, mass, spin, attitude, orbit, and responsiveness of the target object, as well as the environmental conditions such as lighting, temperature, radiation, and atmospheric drag. Moreover, the technologies need to be tested and validated in orbit before they can be used for operational missions.
- Legal challenges: Space junk removal raises several legal issues that need to be addressed by the international community. For example, who is responsible for authorizing, regulating, and supervising space junk removal activities? Who is liable for any damage or injury caused by space junk removal operations? Who owns the rights to the removed debris or any valuable components or materials recovered from it? How can the compliance with the existing treaties and norms of space law be ensured? How can the transparency and accountability of space junk removal activities be enhanced?
- Economic challenges: Space junk removal is an expensive endeavor that requires significant investments in research, development, testing, launch, operation, and insurance. The costs of space junk removal may not be justified by the benefits for individual actors, especially if they do not own or operate the debris to be removed. Therefore, there is a need to develop viable business models and funding mechanisms that can incentivize and reward space junk removal efforts. For example, how can the costs and benefits of space junk removal be shared among different stakeholders? How can the value of preserving the orbital environment be quantified and monetized? How can the market demand and supply for space junk removal services be stimulated and matched?
- Political challenges: Space junk removal involves multiple actors with different interests, perspectives, and capabilities. These actors include states, intergovernmental organizations, private companies, non-governmental organizations, and civil society. Therefore, there is a need to foster cooperation and coordination among these actors to ensure the effectiveness and legitimacy of space junk removal activities. For example, how can the common goals and standards for space junk removal be established and agreed upon? How can the trust and confidence among different actors be built and maintained? How can the potential conflicts or disputes over space junk removal be prevented or resolved?
Despite these challenges, space junk removal also offers many opportunities for innovation, collaboration, and leadership in the space sector. Some of these opportunities are:
- Innovation opportunities: Space junk removal stimulates the development and advancement of new technologies and capabilities that can enhance the performance and safety of space activities. The technologies for space junk removal can also have spin-off applications in other domains such as robotics, artificial intelligence, materials science, or energy. Moreover, space junk removal creates new markets and niches for existing or emerging actors that can provide solutions or services for space debris mitigation or remediation.
- Collaboration opportunities: Space junk removal encourages the cooperation and partnership among different actors that share a common interest in preserving the orbital environment. Space junk removal can also foster dialogue and exchange among different actors that have different views or approaches on how to deal with space debris. Moreover, space junk removal can facilitate the integration and coordination of different actors that have complementary resources or expertise for space debris management.
- Leadership opportunities: Space junk removal demonstrates the commitment and responsibility of different actors to protect the orbital environment and ensure its sustainable use. Space junk removal also showcases the vision and initiative of different actors to address a global challenge that affects all humanity. Moreover, space junk removal enhances the reputation and influence of different actors in the international arena as leaders in space governance.
Conclusion
Space junk is a serious problem that threatens the future of space exploration and exploitation. Therefore, it is imperative to develop and implement effective solutions for space junk cleanup.
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