Nuclear Power in Space: Safety, Governance and India’s Role

Why in News?

Countries are developing nuclear-energy systems for deep-space missions and permanent bases on the Moon and Mars. This has raised concerns regarding launch accidents, radioactive contamination, international liability and whether existing space laws adequately cover high-power reactors and nuclear propulsion.

Why is Nuclear Power Needed in Space?

Solar power remains the main energy source for spacecraft, but it has limitations:

• sunlight weakens with increasing distance from the Sun;
• permanently shadowed lunar regions receive little or no sunlight;
• long lunar nights interrupt solar generation;
• and extreme temperatures and radiation affect solar panels.

Nuclear systems can provide:

• compact and continuous power;
• energy independent of sunlight;
• heat in extremely cold environments;
• and high power for habitats, life support and propulsion.

Radioisotope systems have supported space missions since 1961.

How is Nuclear Energy Used in Space?

Nuclear energy is used through two broad systems: radioisotope systems and fission systems.

Radioisotope Thermoelectric Generators

• RTGs use heat released through the natural decay of radioactive material, usually plutonium-238.
• They convert this heat into electricity.
• They contain no moving parts.
• They can produce electricity and heat for decades.

RTGs have powered:

• Voyager 1 and 2;
• Curiosity rover;
• and Perseverance rover.

The Voyager spacecraft were launched in 1977 for missions expected to last five years but have remained operational for nearly half a century.

Radioisotope Heater Units

• RHUs do not produce electricity.
• They provide heat to prevent instruments and batteries from freezing.

Fission Reactors

• Fission reactors generate heat through a controlled nuclear chain reaction.
• This heat is converted into electricity.
• They provide much higher power than radioisotope systems.

They are suitable for:

• lunar and Martian habitats;
• life-support systems;
• communications;
• scientific equipment;
• and resource extraction.

How Can Nuclear Energy Propel Spacecraft?

Nuclear Thermal Propulsion

• NTP uses a reactor to heat a propellant such as liquid hydrogen.
• The heated propellant is expelled through a nozzle to produce thrust.
• It can provide nearly twice the propellant efficiency of advanced chemical rockets.

Nuclear Electric Propulsion

• NEP converts reactor heat into electricity.
• Electricity accelerates an ionised propellant.
• It provides low thrust but very high efficiency.
• It is suitable for long deep-space journeys.

Shorter journeys to Mars could reduce astronauts’ radiation exposure and allow spacecraft to carry more cargo.

What are the Major Applications?

Deep-space Missions

• Beyond Mars, sunlight becomes too weak for many high-energy missions.
• Nuclear systems can function continuously in dark and cold environments.
• Voyager spacecraft, now more than 20 billion kilometres from Earth, continue to use radioisotope power.

Lunar Exploration

• Permanently shadowed regions near the lunar south pole may contain water ice.
• Nuclear systems can provide reliable energy where sunlight is unavailable.

Long-duration Human Missions

Nuclear energy can support:

• permanent habitats;
• life-support systems;
• communication networks;
• scientific instruments;
• and oxygen and water extraction from lunar soil.

Future Space Economy

Continuous power could support long-term settlements, scientific stations and industrial infrastructure on the Moon and Mars.

What are India’s Plans?

• In 2021, ISRO invited proposals to develop a 100-watt RTG for future deep-space missions.
• India is planning:
  • human spaceflight missions;
  • an Indian space station;
  • deep-space exploration;
  • and a future human landing on the Moon.
• NASA has invited ISRO to participate in its Moon Base programme.
• India can contribute to the development of global safety and regulatory standards.

What are Other Countries Planning?

United States

• NASA’s Dragonfly mission to Saturn’s moon Titan is scheduled for launch in July 2028 and will use a radioisotope generator.
• In August 2025, NASA announced plans for a lunar fission system of at least 100 kilowatts, targeted for deployment by the first quarter of financial year 2030.
• An April 2026 White House memorandum proposed:
  • 20-kilowatt reactors in orbit by 2028;
  • reactors on the Moon by 2030;
  • and higher-power systems during the 2030s.

China and Russia

• China and Russia plan to place a reactor on the Moon by the mid-2030s to support their proposed International Lunar Research Station.

How is Space-based Nuclear Power Regulated?

Outer Space Treaty, 1967

The Treaty:

• requires space activities to follow international law;
• prohibits nuclear weapons and other weapons of mass destruction in orbit or on celestial bodies;
• makes States responsible for national space activities, including those of private companies;
• and requires States to avoid harmful contamination of outer space and celestial bodies.

It prohibits nuclear weapons but does not prohibit peaceful nuclear-power systems.

Liability Convention, 1972

The Convention on International Liability for Damage Caused by Space Objects makes the launching State absolutely liable for damage caused:

• on Earth;
• or to aircraft in flight.

Cosmos 954 Incident

• In 1978, the Soviet satellite Cosmos 954 re-entered over northern Canada.
• Radioactive debris from its reactor was scattered over the region.
• Canada sought compensation.
• The dispute was settled in 1981 for C$3 million.

UN Principles on Nuclear Power Sources, 1992

These principles cover:

• safety assessment;
• radiation protection;
• and notification before the re-entry of a nuclear-powered object.

However, they apply mainly to nuclear sources generating electricity for non-propulsive purposes. They do not comprehensively govern nuclear propulsion.

COPUOS–IAEA Safety Framework, 2009

The framework was developed jointly by:

• the UN Committee on the Peaceful Uses of Outer Space; and
• the International Atomic Energy Agency.

It provides guidance on safety during:

• launch;
• operation;
• and the end of a mission.

However, it is not a complete binding regulatory regime.

What are the Major Challenges?

Launch and Re-entry Risks

Nuclear systems must be capable of surviving:

• rocket explosions;
• launch failures;
• accidental re-entry;
• and impact on Earth without releasing radioactive material.

Radiation Protection

• Reactors require shielding and strict operational controls to protect astronauts, equipment and the space environment.

Technological Immaturity

• Nuclear propulsion is still at an early stage and requires extensive testing before regular use.

Plutonium-238 Shortage

• Plutonium-238 is essential for many RTGs.
• Its availability is limited.
• The United States restarted its production in 2015 after a gap of nearly three decades.

High Technical Requirements

Space nuclear systems require:

• specialised materials;
• extensive ground testing;
• secure reactor controls;
• radiation shielding;
• and safe disposal arrangements.

Way Forward

• Common Standards: Develop global standards for design, testing, launch, operation and disposal.
• Update UN Principles: Extend the 1992 principles to cover nuclear propulsion and high-power reactors.
• Binding Rules: Gradually convert voluntary guidance into enforceable international obligations.
• Safety Assessment: Require transparent pre-launch safety and environmental-impact assessments.
• Emergency Cooperation: Establish international notification and response systems for accidents.
• Clear Liability: Define responsibility where governments and private companies jointly conduct missions.
• Safe Disposal: Create rules for decommissioned reactors and radioactive material.
• Technology Cooperation: Share expertise in shielding, containment and accident-resistant reactor design.
• India’s Participation: India should actively contribute through COPUOS and other international platforms.

Conclusion

Nuclear power can enable deep-space exploration, permanent lunar bases and faster human missions where solar power is insufficient. However, technological progress must be supported by strong engineering safeguards, transparent risk assessment and effective international regulation. Global cooperation is essential to ensure that nuclear power serves peaceful exploration without creating unacceptable risks for Earth or outer space.