Work Stream 3: Outer Space

Penholder: Alexander Glaser (Princeton University)

The last decade has seen a dramatic increase in human activities in space. In addition to the traditional spacefaring powers, many new countries, companies, and even private individuals are entering the field. At the same time, space is increasingly seen as a competitive, congested, and contested environment, where “being first” is often considered imperative. The Artemis Program led by the United States seeks to establish by 2030 a permanent lunar outpost powered by a fission power source. Efforts led by China and Russia to establish an International Lunar Research Station (ILRS) envision a similar timeline.

There are at least two major challenges with regard to nuclear verification in and for outer space — and both have possible implications for future nuclear disarmament efforts. They include, first, the possible deployment of nuclear weapons in space and, second, proliferation risks and associated safeguards for nuclear materials produced for and launched into space. Our research efforts undertaken as part of this work stream will address both these aspects.

On the Possible Deployment of Nuclear Weapons in Space

The deployment of nuclear weapons in Earth orbit and on celestial bodies, including the Moon, is prohibited by the 1967 Outer Space Treaty (OST). Partly due to technical limitations at the time, the OST remains unverified. While concerns about the placement of nuclear weapons in space waned with the end of the Cold War, since 2024, there have been allegations that Russia might be pursuing a program that would be in violation of the OST. There currently exist no viable mechanisms for resolving such matters.

As part of the efforts planned for this work stream, we will first assess possible reasons why nuclear weapon states might consider the deployment of nuclear weapons in space today. This may in turn help inform future discussions about possible policy options and verification approaches to address some of these concerns.

Importantly, new technical developments may now or soon enable certain in-orbit inspections of satellites, leveraging close-proximity and rendezvous operations, and the use of satellite formations, which can approach other satellites to distances of less than one kilometer.

This is often done in a non-cooperative manner, i.e., without approval or knowledge of the operators of the inspected satellite. Our effort will review and assess some ongoing technical developments and opportunities in this area, with a special focus on possible transparency measures and cooperative approaches that could be coordinated among relevant parties. We also examine, in particular, the trade-offs between pre-launch and on-orbit inspections that could help confirm compliance of missions involving nuclear payloads.

On nuclear-fuel cycle activities and best practices on Earth

The use of nuclear reactors in space could ultimately become common practice if new types of space missions are pursued: these include permanent lunar outposts, deep-space missions, including perhaps crewed missions to Mars, as well as high-powered civilian or military applications in Earth orbit. Most likely, only nuclear power would meet the power and endurance requirements for such missions. The use of nuclear power in space is not prohibited but, according to UN General Assembly Resolution 47/68 from 1992, its use “in outer space shall be restricted to those space missions that cannot be operated by non-nuclear energy sources in a reasonable way.” The same resolution also stipulates that “nuclear reactors shall use only highly enriched uranium 235 as fuel” — which is inconsistent with current nonproliferation policies that strongly favor enrichment levels below 20% in the isotope U-235. Since space missions prioritize minimum weight, compactness, and high endurance, there are strong incentives to use fuels with high enrichments. National security considerations that are often associated with space activities could encourage additional countries to pursue sensitive domestic nuclear capabilities rather than relying on foreign suppliers. In short, the use of nuclear power in space could have profound implications for nuclear fuel-cycle activities and best practices on Earth.

With regard to nuclear safeguards, there are unresolved questions about the fate of nuclear materials once launched into space, for example, possible monitoring options for spent nuclear fuel in reactor cores that have reached their end-of-life or were shutdown prematurely. This work stream seeks to provide an in-depth analysis of these aspects, including the usefulness of pre-launch inspections to address some of the verification challenges related to nuclear power in space.

Other collaborators for this work stream include Roohi Dalal, Areg Danagoulian (MIT), Sarah Erickson (UMD), Steve Fetter (UMD), Carolin Früh (Purdue), Jeffrey Lewis (CNS/MIIS), Laura Rockwood (VCDNP), Raven Witherspoon (Princeton), and Vivienne Zhang.