Space, the Final Frontier of International Nuclear Law
This blog post is adapted from an essay I submitted to the International Atomic Energy Agency’s first International Conference on Nuclear Law. Additionally, I gave a keynote speech (available here) at the conference on the need to create a new discipline for space nuclear law.
A global space rush is emerging as rapid decreases in the cost of launching rockets and building satellites enable countries to harness economic and power benefits on the final frontier. Governments and companies are looking at mining the Moon, travelling to Mars, or establishing satellite mega-constellations to provide Earth-bound services. Great and emerging powers are reevaluating space as a realm of strategic competition and warfare. In this context, many countries are now pursuing space nuclear power systems to achieve hard and soft power.
Due to energy density and reliability, space nuclear systems are an enabling technology for government and commercial purposes. Accordingly, establishing a strong governance system for these technologies under international space and nuclear law is an imperative to minimize conflict and negative impacts.
Provisions of both space and nuclear law apply to national nuclear activities in space. However, there are potential gaps, particularly as nuclear law is not fully developed when it comes to transportable reactors and non-power applications.
This essay examines the status of international law governing space nuclear power systems, with a particular focus on identifying gaps in the four traditional areas of nuclear law: non-proliferation, security, safety, and liability. As nations turn to nuclear power to travel the stars, they should provide thoughtful consideration of the nuclear governance framework underlying such activities.
Per Nuclear Ad Astra
Technology innovation and commercialization in both the space and nuclear sectors are leading to the development of space nuclear power for the first time since the Cold War. Critically, unlike early space nuclear activities, commercial entities are now playing a leading role due to their ability to rapidly commercialize technologies and the advantages of nuclear power to meet private sector demand in outer space. Among other interested nations, the U.S., Russia, and China are each pursuing the three major types of space nuclear power: radioisotopes, fission power, and fission propulsion.
Source: INL
Further, while still in its infancy, the ongoing wave of fusion innovation also includes companies aiming to develop fusion propulsion.
As this renaissance in space nuclear technology emerges, it raises novel legal questions about the application of nuclear law to the global commons of outer space. Early nuclear-powered missions led to notable accidents with legal implications, including a Soviet reactor crashing in Canada, multiple launch failures and unplanned reentries, and a satellite collision with a decommissioned reactor leading to a radioactive space debris cloud.
Space nuclear activities are governed by a mix of international space and nuclear treaties. The most important is the Outer Space Treaty (OST), the ‘constitution’ of international space law. The OST establishes outer space as an area beyond national jurisdiction with free access and use by countries for peaceful purposes. Further, the OST extends the international system to include a state’s activities in space. This means that treaties governing nuclear power, such as the Nuclear Non-Proliferation Treaty, generally apply to a state’s activities both on Earth and in space.
Two other relevant space treaties establish a space liability regime and develop a registration system for a state’s space objects. Together the three treaties create the concept of a “launching state;” effectively, a state that launches something into space retains jurisdiction over and responsibility for that object. Any national space nuclear activities will occur within this international legal framework for space activities which, like most of international law, primarily governs relations between states. The OST specifically obligates a state to authorize and oversee space activities of their nationals, meaning that governments are responsible for private commercial space nuclear missions.
While most of the space treaties apply to space nuclear missions, existing international statutory nuclear law has limited applicability to spacecraft with nuclear systems. The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) certainly applies and provides strong protections against proliferation. Notably, the two accident conventions were negotiated in part due to the a Soviet space reactor crashing into Canada. The Convention on the Physical Protection of Nuclear Materials may apply to certain parts of the supply chain for space nuclear missions.
However, other major treaties are explicitly limited to terrestrial reactors, namely the Convention on Nuclear Safety and the three liability treaties. Although there are several soft law instruments regarding space nuclear governance, these are non-binding and only provide the most basic of guidance to states. Finally, with limited space nuclear missions, no commercial missions to date, and no explicit case law, international customary law is unlikely to directly handle the unique characteristics of space nuclear missions.
Four Pillars of International Nuclear Law
With this context, reviewing each of the four primary areas of traditional international nuclear law indicates that even though existing governance may be sufficient for early missions, states may wish to further develop statutory and customary law to govern long-term, widespread use of space nuclear systems.
Pillar 1. Non-proliferation
Source: Brookings
The most worrying area of nuclear law, non-proliferation, is likely the one with the greatest international obligations and precedents related to space activities. The OST itself was originally conceived in part as one of the first arms controls treaties during the Cold War. Fearful of space-based nuclear weapons, the U.S. and Soviet Union pushed for Article IV, which prohibits the stationing of weapons of mass destruction in orbit or on celestial bodies. When combined with the OST’s invocation of general international law, and hence state obligations under the non-proliferation treaty, state use of nuclear energy in outer space must be conducted in a way that does not promote proliferation.
Even though the OST is not universally recognized, there is likely sufficient precedent that space is part of the international domain under customary law. This means, as the NPT has almost universal participation, any use of nuclear materials in space would likely require national controls, even for a commercial space nuclear system. Non-weapons states cannot use the space domain to develop nuclear weapons openly or clandestinely, and any use of nuclear energy by a non-weapon state would be subject to relevant safeguards.
Nevertheless, while state obligations are clear, there are opportunities for early leaders to establish norms. The U.S. provides a good example – following non-proliferations concerns that arose from the use of highly enriched uranium (HEU) for a prototype space reactor (Kilopower), U.S. policy has quickly moved to favor low enriched uranium (LEU). Considering the many commercial entities that are interested in space activities, a strong international norm of prioritizing LEU can complement the statutory constraints on proliferation in outer space. However, excluding HEU as a design option only underscores the importance of establishing terrestrial HALEU supply chains.
Pillar 2. Safety
The legacy process for space nuclear launch approval in the U.S. required many years to obtain environmental permits, conduct safety analysis, receive safety reviews, and obtain White House launch approval. Source: IDA
State obligations and practice for the safety of space nuclear systems are largely absent from international law. As mentioned earlier, the Convention on Nuclear Safety is focused exclusively on terrestrial reactors, not on space reactors or other non-power applications of space nuclear energy. The 2009 COPOUS-IAEA “Safety Framework for Nuclear Power Source Applications in Outer Space” provides the primary soft law guidance. While useful, the document is only 7 pages of text.
Safety analyses of past government missions were handled via state agencies based on internal standards. Generally the goal of such safety analyses is to identify and avoid prompt criticality of a reactor or dispersal of radioactive materials during a launch accident or subsequent accidental reentry.
National regulators of nuclear power typically only have experience with terrestrial research reactors or large commercial light-water reactors (in part due to international norms regarding nuclear regulators). It is not clear that such regulators have sufficient expertise in relevant safety considerations for the launch and operations of a space nuclear system.
In many cases, states may regulate the commercial launch of a nuclear reactor through their general launch regulator, like the Federal Aviation Administration in the United States. The United States, informed in part by the COPOUS-IAEA Safety Framework, issued an executive order in 2019 substantially reforming launch processes, including designating FAA as the commerical launch regulator.
However, even if launch regulators are in a position to make such technical analyses across multiple disciplines, there are no clear norms or precedent guiding their analyses, particularly for reactors. Further, it is not clear that nations are planning to regulate for safety once a reactor is in orbit or on a celestial body. In many cases, existing space safety standards related to astronauts, planetary protection, harmful contamination, space debris, or other factors may shape safety outcomes. Thus, nuclear safety regulation of space operations with these areas in mind is a critical area for future industry and legal development, especially acknowleding space is an inherently international domain with many states as stakeholders.
Pillar 3. Security
Nuclear materials security across the supply chain and at the launch site is a critical element of a successful space nuclear launch, yet considerations of security during space operations is in its infancy. Source: NASA
Nuclear security for space nuclear systems is another area where states should place a high priority on legal development. Although space nuclear systems require security for terrestrial supply chains, existing controls on the ground for government and commercial activities are well established and likely sufficient. However, there is concern about tracking and securing nuclear materials in the case of a launch accident, especially for an HEU-fueled reactors.
Considering the unique nature of outer space, physical security of a launched space nuclear system from non-state actors is likely to be of limited concern. However, as most of these systems are likely to be remotely operated, cyber security is of paramount importance. Broader discussions about cybersecurity for the nuclear and space sectors should incorporate specific space nuclear concerns.
Beyond security concerns related to nuclear materials, sabotage, and non-state actors, the potential use of space nuclear systems for military operations raises concerns under international humanitarian law, otherwise known as the law of armed conflict. Despite some belief to the contrary, the OST is not generally held to prohibit warfare in space, although it does prohibit stationing of weapons of mass destruction or construction of military bases on celestial bodies.
If a state were to target the space nuclear system of another state for military reasons, traditional rules governing armed conduct, like proportionality, apply. However, there are likely to be many existing technical gaps regarding the damages and broader impacts of destroying a space reactor that would inhibit comprehensive legal analysis. The unique nature of orbital environments can create novel debris risks while the fragile nature of planetary surfaces could exacerbate the effects of a damaged reactor. Accordingly, as states increasingly view space as a warfighting domain, any international discussion on conflict in space should consider relevant restrictions regarding targeting space nuclear systems.
Pillar 4. Liability
Graphic of debris from the Cosmos-Iridium collision that increased the overall debris population by ~20%. Source: Celestrak
Finally, the existing state of international space liability is likely to provide a strong basis for governing space nuclear systems even though existing nuclear liability treaties remain constrained to terrestrial reactors. Currently, space liability is primarily shaped by the OST and space liability treaty. Under these treaties, a launching state is liable for any damages to Earth and terrestrial states due to their space activities, including space nuclear systems (i.e. strict liability).
A state only incurs liability for damages in outer space if they are at fault. Fault, negligence, and attribution can be very difficult to define and prove in the space environment. The space liability regime has yet to be seriously tested. The two most salient case studies involve Soviet space reactors, the 1978 crash in Canada and the Cosmos-Iridium collision, but were both settled outside of the provisions of the space liability convention.
Looking forward, the space liability regime incorporates some key principles of the terrestrial nuclear liability regime. By tying strict liability for Earth damages and at fault liability for space damages to a spacecraft’s launching state, the regime places liability on the entity best able to minimize accidents, the operator.
Nevertheless, states should consider how to incorporate best practices of nuclear liability law into space liability law. Critically, space liability currently governs state-to-state issues and does contain clear guidelines for how to impute state-level liabilities to commercial actors such as a developer of a space nuclear system. As seen in nuclear liability frameworks, addressing cross-border liabilities of commercial entities is critical to facilitate international trade in space nuclear systems.
A New Frontier for Law
Space nuclear energy technologies offer many new opportunities for science and commerce on the final frontier. They can power near-term science on the Moon, power space mines to produce water and metals, and even support Mars exploration. By complementing terrestrial nuclear innovation, they can accelerate overall nuclear technology development. However, space nuclear systems also bring unique risks and controversies which require careful development of law.
International space and nuclear law provides the general framework for governance of these technologies. As governments pursue more space nuclear missions, and private entities launch nuclear spacecraft for the first time, the nuclear and space law communities should proactively work to build effective governance for the long-term. Proliferation and liability have a strong statutory basis but require significant implementation work. Safety and security lack that statutory basis, compounded by technical questions regarding actual risks. Ultimately, effective governance to harness the atom safely is needed because it can unlock the commercial and scientific benefits of space exploration.
Broadly, the development a space nuclear discipline can inform both space law and nuclear law. Regulating highly technical, engineered systems requires the development of parallel regulatory principles which can lead to best practices across sytems. Ultimately, more robust space and nuclear law can reduce risk of conflict in space, unlock the space economy, and even catalyze accelerated development of technologies that can mitigate climate change.
Additional Resources
National Research Council. “Priorities in Space Science Enabled by Nuclear Power and Propulsion.”
National Academies of Sciences, Engineering, and Medicine. “Space Nuclear Propulsion for Human Mars Exploration.”
IAEA. “The Role of Nuclear Power and Nuclear Propulsion in the Peaceful Exploration of Space.”
