The science, technology, and pitfalls of using nuclear power in space

The US recently announced plans under its Lunar Fission Surface Power Project to deploy a small nuclear reactor on the moon by the early 2030s. It could be the first attempt to establish a permanent nuclear power source beyond earth orbit, signalling the start of a new era in space.
While solar energy can power some simple moon-based activities, it’s constrained by the two-week-long lunar nights and the scarcity of sunlight at the poles. For a sustained moon and Mars presence, humans’ energy independence thus becomes a critical enabler. This is also why the US’s lunar nuclear programme is notable.
Promise of nuclear power
In conversations on this topic on the earth, nuclear power often features as an alternative that is compact, dense, and reliable.
Devices called radioisotope thermoelectric generators (RTGs) have powered the Voyager spacecrafts’ odyssey through the solar system. They convert heat released by the slow decay of plutonium-238 nuclei into electricity, and are immune to dust and darkness. But RTGs only produce a few hundred watts of electric power, enough for instruments but insufficient for human habitats or industrial operations.
Compact fission reactors are the next leap. About the size of a shipping container, these reactors can generate tens to hundreds of kilowatts, and can power life support, laboratories, and manufacturing units.
The next leap on the demand side will be industrial operations like in-situ resource utilisation, which can convert Martian water ice into rocket fuel and oxygen, which need over 1 MW of continuous power. Sunlight alone can’t reliably supply this magnitude beyond the earth’s orbit. This is where nuclear power reactors are attractive.
On Mars, reactors buried beneath the regolith could take advantage of the natural shielding to protect equipment and inhabitants from cosmic radiation while producing large amounts of energy. The idea of deploying such reactors on the moon itself is lucrative, where they can help maintain warm habitats for explorers, process ice for water and rocket fuel, and recharge batteries for surface mobility vehicles.
Incremental advances in nuclear power have enabled new technologies that were once confined to science fiction. Beyond RTGs, there is now nuclear thermal propulsion, where a propellant is heated by nuclear decay and expelled from nozzles. The DRACO programme in the USA will test this technology in lunar orbit by 2026. If it works, the trips to Mars could become several months shorter, slashing crew exposure to galactic cosmic rays.
In nuclear electric propulsion, reactor-generated electricity ionises a propellant, offering years of efficient thrust for deep-space probes and cargo missions.
Legal vacuum
The international framework for nuclear power in space is based on the 1992 United Nations Principles Relevant to the Use of Nuclear Power Sources in Outer Space (UNGA Resolution 47/68). These Principles impose several procedural and safety obligations on launching states for systems used to generate electricity.
Three Principles in particular are relevant. No. 3 mandates nuclear power sources to be designed and built to prevent the release of radioactive materials in both normal and emergency conditions. No. 4 requires rigorous pre-launch safety analyses to make sure the probability of accidental release is acceptably low. No. 7 further aligns with existing space treaties by requiring prompt and clear emergency notification to any potentially affected state in the event of a malfunction or reentry involving radioactive materials.
However, this framework is limited. The Principles address only RTGs and fission reactors intended for electricity generation, and not nuclear thermal/electric propulsion systems. And while they call for safety assessments, they don’t establish binding technical standards for reactor design, operational limits, and end-of-life disposal.
Crucially, as a General Assembly resolution, the Principles are non-binding, meaning they offer guidance but no enforcement mechanism. This leaves significant governance gaps. Among other possibilities, states can begin testing compact fission and propulsion reactors capable of operating far beyond the earth orbit without being compelled to address safety.
Beyond those Principles, the Outer Space Treaty, the Liability Convention, and the Nuclear Non-Proliferation Treaty together only offer partial coverage. For instance, even if they are all considered together, there are no binding protocols to prevent radioactive contamination of celestial bodies or to govern reactors jettisoned at the end of a mission.
Without such protocols, nuclear contamination could irreversibly alter pristine extraterrestrial environments long before humankind fully understands them. The tension between safety and international access is also paramount. As the European Space Agency’s special advisor for political affairs Kai-Uwe Schrogl has noted: “Establishing ‘safety zones’ around nuclear power plants on celestial bodies must not lead to national appropriation or the restriction of freedom of use for other actors.”
Responsible race
As the human presence in the solar system expands, energy will become critical and energy sources will become strategic.
For now, while the Outer Space Treaty forbids countries from placing weapons of mass destruction in earth orbit, it’s silent on nuclear propulsion for peaceful purposes. The Liability Convention addresses damage caused by space objects but isn’t clear about accidents involving nuclear reactors in cis-lunar space or beyond.
For these reasons, we need to update the legal framework posthaste to match countries’ technological capabilities or risk accidents that could have long-lasting consequences across state boundaries. In fact, if such an accident does occur, the promising nuclear dawn will quickly devolve into a nuclear twilight, if not a second Cold War.
India’s moment
India itself stands at a strategic inflection point. An alliance of the Indian Space Research Organisation (ISRO) and the Department of Atomic Energy could be powerful. A domestically developed space reactor could power lunar operations in permanently shadowed craters, enable continuous in-situ resource utilisation on Mars, and overall demonstrate India’s leadership in deep-space innovation.
But both in India and around the world, a responsible nuclear future needs to begin with reform. The UN’s 1992 Principles should be updated to explicitly include propulsion reactors, establish safety benchmarks, and define end-of-life disposal standards. The UN Committee on the Peaceful Uses of Outer Space needs to adopt binding environmental protocols to govern safe launches, preventing contamination, and disposing of nuclear systems. To this end a multilateral oversight mechanism modelled on the International Atomic Energy Agency could certify designs, verify compliance, and enhance transparency.
This said, technology alone can’t secure our future. Without a coherent legal and ethical framework, efforts to expand nuclear technologies in space could give way to conflict.
India in particular can help by championing safe nuclear practices, and do for space energy what it once did for non-aligned diplomacy: shape norms for a multipolar era by balancing ambition with restraint.