NASA Funds New Nuclear-Power Concept for Future Interstellar Missions

NASA selected a University of Utah concept for a highly efficient radioisotope power generator that could give future interstellar spacecraft far more electricity without dramatically increasing their mass.

Editorial Note

This article is provided for general educational and informational purposes. It is based primarily on information published by NASA about a concept selected through the NASA Innovative Advanced Concepts program.

The proposed power system remains an early Phase I feasibility study. NASA has not approved it for construction, flight testing or use aboard an interstellar mission. Its projected efficiency and power-to-mass performance are engineering goals that must be tested and independently validated.

References to nuclear power in this article concern radioisotope power systems designed to convert heat from the natural decay of nuclear material into electricity. These systems are different from conventional nuclear reactors and do not generate energy through a sustained fission chain reaction.

Future spacecraft traveling toward the outer solar system—or perhaps eventually into interstellar space—will face a stubborn engineering problem: sunlight becomes increasingly weak as a mission travels farther from the Sun.

Solar panels that work well near Earth become less practical at extreme distances. Batteries eventually lose their charge. A spacecraft may need to operate for decades while powering computers, communication equipment, heaters and scientific instruments without access to maintenance or refueling.

NASA is now supporting an early-stage concept that could dramatically improve how long-distance spacecraft generate electricity.

On July 21, 2026, NASA published details of a proposal called the Plasmon-Enhanced Radioisotope Thermophotovoltaic generator, or PRTPV. The concept was selected for a Phase I study through the NASA Innovative Advanced Concepts program and is being led by Keunhan Park of the University of Utah.

The proposed system would use heat produced by radioactive decay, but it would convert that heat into electricity differently from the radioisotope thermoelectric generators used on spacecraft such as Voyager, New Horizons, Curiosity and Perseverance.

Its developers are targeting a thermal-to-electric conversion efficiency above 40% and a specific power of approximately 17 watts per kilogram. NASA’s project description says those goals would represent about a sevenfold efficiency improvement and nearly an order-of-magnitude increase in specific power compared with current advanced radioisotope thermoelectric generators.

If those targets can eventually be achieved outside the laboratory, spacecraft could produce more electricity from the same amount of radioactive heat—or carry a smaller and lighter power system while maintaining the electricity required for a mission.

That would not immediately make travel to another star possible. It could, however, remove one of the major obstacles facing spacecraft designed to operate for decades in places where conventional solar power is no longer practical.

What NASA Selected

The PRTPV proposal was included among NASA’s 2026 NIAC Phase I selections.

NIAC supports unconventional aerospace concepts that could transform future missions. The program is designed to investigate ideas that are technically ambitious and may be years or decades away from operational use.

A Phase I selection generally supports an initial feasibility study rather than the development of flight-ready hardware. NASA’s current NIAC schedule describes Phase I awards as nine-month studies funded at up to $225,000.

Researchers use that period to refine the scientific basis of a concept, identify engineering challenges and determine whether further development is justified. Even a successful Phase I study does not guarantee progression to later NIAC phases or adoption by a NASA mission.

The distinction matters because NASA did not announce a new spacecraft powered by PRTPV technology.

It selected a proposal to determine whether such a power system could realistically deliver the performance its designers predict.

Why Deep-Space Missions Need Nuclear Power

Most spacecraft operating near Earth use solar panels. Sunlight strikes photovoltaic cells, which convert part of that energy into electricity.

That approach is renewable, relatively well understood and effective where sunlight remains strong enough.

The difficulty is distance.

The farther a spacecraft travels from the Sun, the less solar energy reaches each unit of panel area. A mission traveling into the outer solar system may require extremely large arrays, specialized low-light solar cells or another power source entirely.

Sunlight may also be obstructed by dust, clouds, darkness, terrain or the conditions surrounding a destination.

NASA therefore uses radioisotope power systems for certain missions that must survive where solar energy is limited or unreliable. These systems use heat released through the natural decay of radioactive material and convert it into electrical power. They can also provide useful heat for instruments and spacecraft systems operating in extremely cold environments.

NASA and the U.S. Department of Energy work together on radioisotope power. The Department of Energy manages the nuclear material and the development of the power systems, while NASA determines the requirements for missions that may need the technology.

How a Traditional RTG Works

A radioisotope thermoelectric generator, commonly called an RTG, does not operate like a nuclear power plant.

There is no sustained nuclear chain reaction. Instead, material such as plutonium-238 naturally decays and releases heat.

Thermoelectric materials convert part of the temperature difference between the hot radioisotope source and the colder environment into electricity.

RTGs have few moving parts and can operate reliably for decades. That reliability is one reason they have powered some of NASA’s most distant and long-lived missions.

Voyager 1 and Voyager 2 continue communicating from interstellar space because their radioisotope power systems have supplied electricity far beyond the useful lifetime expected from ordinary batteries. New Horizons used an RTG during its journey to Pluto, while Curiosity and Perseverance use radioisotope systems on Mars.

A total of 24 NASA missions have flown successfully with radioisotope power systems since 1969. NASA’s Dragonfly mission to Saturn’s moon Titan is also being developed to use radioisotope power.

The major limitation is efficiency.

Traditional thermoelectric conversion sends only part of the heat into usable electrical power. The remaining energy is released as waste heat, although some can be used to keep spacecraft components warm.

For missions with high electrical demands, engineers may need more nuclear material, a heavier generator or strict limits on the instruments that can operate simultaneously.

How the PRTPV Concept Would Be Different

The proposed PRTPV system would still begin with heat from radioactive decay.

Instead of relying primarily on thermoelectric materials, it would use thermophotovoltaic conversion.

In simplified terms, the radioisotope heat source would produce thermal radiation. Specially designed photovoltaic cells would then convert selected wavelengths of that radiation into electricity.

This is conceptually similar to a solar cell converting sunlight, except the energy source would be radiation emitted from a hot internal surface rather than light arriving from the Sun.

The challenge is that ordinary thermal radiation contains a broad range of wavelengths. Not every wavelength can be converted efficiently by a given photovoltaic cell.

The PRTPV proposal attempts to solve that problem with advanced materials and a structure designed to tune the radiation before it reaches the photovoltaic component.

Why Plasmons Matter

The word “plasmon” in PRTPV refers to collective oscillations of electrons that can occur at the boundary between certain materials.

Engineers can use these interactions to control how light and thermal radiation behave at extremely small scales.

The proposed generator would include a multilayer photonic-crystal plasmon coupler. Its purpose would be to concentrate and tune the thermal radiation so that more of it matches the energy range the photovoltaic cell can convert efficiently.

Rather than allowing much of the heat to radiate in unusable wavelengths, the system would attempt to direct more of that energy toward the cell’s optimal bandgap.

The concept also proposes replacing the traditional vacuum gap between the heat source and photovoltaic cell with a material possessing a high refractive index, low infrared loss, low thermal conductivity and a high melting point.

NASA’s description identifies aluminum oxide as one possible material. According to the proposal, this arrangement could increase the density of thermal radiation transferred toward the photovoltaic cell while limiting unwanted direct heat conduction.

That combination of material science, photonics and nuclear power conversion is what makes the concept potentially transformative—and technically difficult.

What 40% Efficiency Could Mean

NASA’s project page says the team is targeting thermal-to-electric efficiency above 40%.

That means more than 40% of the heat directed into the conversion process would ideally emerge as usable electrical energy.

Current radioisotope thermoelectric generators generally convert a much smaller portion of their available thermal power into electricity.

Higher efficiency could create several benefits.

A spacecraft might generate more electrical power from a given amount of plutonium-238. That would help conserve a limited and expensive resource.

A smaller heat source could potentially satisfy the same electrical requirement, lowering the total mass of the power system.

Alternatively, engineers could use the increased electricity to operate more capable instruments, faster computers, stronger communication transmitters or advanced autonomous systems.

Efficiency also affects thermal management. A system that converts more heat into electricity may leave less waste heat that must be rejected or controlled, although spacecraft in very cold environments may deliberately use some waste heat to protect sensitive components.

The proposed 40% figure remains a design goal, not a demonstrated flight-system result.

Laboratory components may achieve encouraging performance under carefully controlled conditions while a complete generator faces losses, material degradation and thermal-management challenges that reduce real-world efficiency.

Why Specific Power Is Equally Important

Efficiency tells engineers how much input heat becomes electricity.

Specific power measures how much electricity a system produces relative to its mass, usually expressed in watts per kilogram.

Mass matters enormously in spaceflight.

Every kilogram launched from Earth requires rocket capacity, structural support and fuel. A heavy power system can reduce the mass available for scientific instruments, communication hardware, shielding or propulsion.

The PRTPV team is targeting approximately 17 watts of electrical output per kilogram of generator mass.

NASA describes that as nearly an order-of-magnitude improvement over current advanced RTGs.

A lighter generator could make it easier to design compact probes or allow a larger spacecraft to carry several high-power instruments without increasing its launch mass dramatically.

For interstellar precursor missions, higher specific power may be especially valuable because such probes must balance extreme durability with the need to remain light enough to reach high speeds.

Would This Generator Power the Spacecraft’s Engines?

A power source and a propulsion system are not necessarily the same thing.

The PRTPV generator is primarily proposed as a way to produce electricity. That electricity could operate the spacecraft’s computers, instruments, heaters and communication systems.

Depending on the mission architecture, it might also support an electric-propulsion system. Electric propulsion uses electrical energy to accelerate propellant, often producing low thrust continuously over long periods.

However, the generator itself would not automatically propel a spacecraft to another star.

Interstellar travel requires overcoming extraordinary distances. Even the nearest star system is more than four light-years away.

A mission would need an advanced propulsion method, a high launch velocity or a combination of technologies capable of reducing travel time from thousands of years to something scientifically useful.

Improved power generation solves only one part of that problem.

It may allow a probe to remain functional after decades of travel, communicate from enormous distances and operate sophisticated scientific instruments once it reaches its destination.

Why Communication Becomes a Power Problem

A distant spacecraft must transmit information back toward Earth.

As the distance increases, its radio signal spreads and becomes progressively weaker by the time it reaches receiving antennas.

A probe traveling far beyond Pluto may need a high-gain antenna, extremely sensitive Earth-based receivers and enough electrical power to operate its transmitter.

Interstellar missions would face an even greater challenge.

A probe might gather valuable data but be unable to return it efficiently without sufficient onboard power. Increasing transmitter strength, processing data before transmission and maintaining precision pointing systems all require electricity.

A higher-performance radioisotope generator could provide more power for communication without making the spacecraft prohibitively heavy.

That may be one of the most practical benefits of the PRTPV concept.

The technology does not have to power an interstellar engine to make an interstellar science mission more achievable. Keeping the spacecraft alive and able to communicate may be just as difficult.

The Plutonium-238 Supply Question

Many NASA radioisotope systems use plutonium-238 because it produces substantial heat, has a predictable decay rate and can provide energy over long missions.

Its half-life is approximately 88 years. This allows the electrical output of an RTG to decline gradually in a way mission engineers can anticipate.

Plutonium-238 is not the material commonly associated with nuclear weapons. Its primary value for spaceflight comes from its heat output rather than its suitability for weapons use.

The supply is still limited and expensive to produce.

NASA and the Department of Energy have worked to reestablish domestic plutonium-238 production after a decades-long gap. Improving conversion efficiency could allow future missions to generate more electricity from the available material.

That could make high-efficiency power conversion valuable even before interstellar missions become realistic.

Outer-planet probes, lunar missions, Mars missions and spacecraft exploring dark or permanently shadowed environments could all benefit from using radioisotope heat more effectively.

What Could Prevent the Concept From Working?

The projected performance is ambitious, and several engineering challenges could emerge.

The materials must tolerate high temperatures and radiation for many years without losing their optical or structural properties.

The photonic and plasmonic structures must remain precisely aligned. Small changes caused by vibration, radiation damage, thermal expansion or material degradation could reduce performance.

The photovoltaic cells must convert the tuned radiation efficiently while surviving continuous exposure to heat.

The generator also needs insulation, shielding, wiring, structural support and thermal controls. Those components add mass, potentially reducing the system’s real specific power below the value predicted for its central conversion technology.

Reliability may be the greatest challenge.

NASA chooses RTGs partly because they have demonstrated decades of dependable operation with no mechanical maintenance. A more efficient generator offers little benefit if its performance declines rapidly or if one delicate component can disable the entire system.

The Phase I study will need to examine whether the proposed advantages can survive the transition from idealized models to a complete, durable power system.

It Is Not a New NASA Mission

The project’s name includes “Power Generation for Interstellar Missions,” but NASA has not announced a mission using the technology.

NIAC deliberately funds ideas that may be far ahead of current mission plans.

Some concepts progress to further research. Others reveal technical barriers that cannot yet be overcome. A few may influence later technologies without ever becoming missions in their original form.

The PRTPV project should therefore be described as a NASA-funded feasibility concept rather than a new spacecraft, finalized generator or scheduled interstellar program.

That does not make the selection insignificant.

Early research programs are where many transformative technologies begin. The purpose of Phase I is to determine whether the underlying physics and engineering are strong enough to justify a larger investment.

What Success Could Mean for Future Exploration

A successful high-efficiency radioisotope power generator could affect more than hypothetical missions to another star.

It could improve probes sent to Uranus, Neptune, Pluto or distant Kuiper Belt objects.

It could support spacecraft operating in permanently shadowed lunar craters, where solar energy is difficult to obtain.

It could power long-lived stations on Mars or scientific instruments deployed beneath the icy surfaces of distant moons.

Smaller generators could also enable networks of compact probes that would otherwise be unable to carry conventional radioisotope systems.

NASA notes that radioisotope power can enable missions in the deepest, darkest, dustiest and most distant environments where solar power, batteries and fuel cells are not sufficient.

PRTPV technology would attempt to make that capability significantly lighter and more efficient.

Why This Matters for Students and STEM Education

The proposal demonstrates how future space exploration depends on more than rockets.

The team must combine nuclear science, heat transfer, photovoltaic engineering, optical physics, nanotechnology, advanced materials and spacecraft design.

Students interested in space may imagine careers as astronauts or astronomers. Projects such as PRTPV show that missions also require specialists who understand energy conversion, material durability and thermal radiation.

The concept provides a useful example of how basic science can become applied engineering.

Plasmons and photonic crystals may sound highly theoretical. In this project, they are being investigated as tools for solving one of spaceflight’s most practical problems: how to keep a spacecraft powered when the Sun is unimaginably far away.

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Key Takeaways

NASA published details on July 21, 2026, of a University of Utah concept called the Plasmon-Enhanced Radioisotope Thermophotovoltaic generator.

The project was selected for a Phase I study through the NASA Innovative Advanced Concepts program. It is an early feasibility concept, not a flight-approved power system or announced interstellar mission.

The proposed generator would convert heat from radioactive decay into electricity using thermophotovoltaic cells, advanced materials and a plasmonic structure that tunes thermal radiation.

Its designers are targeting thermal-to-electric efficiency above 40% and specific power of approximately 17 watts per kilogram.

NASA says those goals would represent about a sevenfold efficiency improvement and nearly an order-of-magnitude increase in specific power compared with state-of-the-art radioisotope thermoelectric generators.

The technology could eventually support interstellar precursor missions, outer-planet probes and spacecraft operating in environments where sunlight is too weak or unreliable for conventional solar power.

Frequently Asked Questions

Did NASA announce an interstellar mission on July 21?

No. NASA selected and published information about an early-stage power-system study. No spacecraft using the system has been approved for launch.

What does PRTPV mean?

PRTPV stands for Plasmon-Enhanced Radioisotope Thermophotovoltaic.

Is the proposed generator a nuclear reactor?

No. It would use heat from the natural decay of radioactive material. It would not rely on a sustained nuclear-fission chain reaction.

How is it different from an RTG?

A traditional RTG uses thermoelectric materials to convert heat directly into electricity. The proposed PRTPV system would use thermally generated radiation, tuned by advanced photonic and plasmonic structures, to power photovoltaic cells.

How efficient could it be?

The researchers are targeting thermal-to-electric conversion efficiency above 40%. That is a proposed engineering target and has not been demonstrated in a flight-ready generator.

Would it allow humans to travel to another star?

Not by itself. It is a power-generation concept, not a complete propulsion system. Interstellar travel would still require major advances in propulsion, communication, shielding and long-duration spacecraft reliability.

Why not use solar panels?

Solar power becomes less practical as a spacecraft travels farther from the Sun. Radioisotope power can operate continuously in dark, dusty, cold or distant environments.

Final Thoughts

Interstellar exploration is often discussed as a propulsion problem.

How can a spacecraft travel fast enough to reach another star within a useful period?

That question is enormous, but it is not the only challenge.

A probe must survive for decades. It must keep its computer and instruments functioning. It must prevent critical systems from freezing and transmit information across distances far greater than those crossed by any current mission.

All of that requires dependable electricity.

The PRTPV proposal is an attempt to generate that power more efficiently and with less mass than conventional radioisotope generators.

Its targets are impressive, but they remain targets. The technology must prove that its advanced materials and precisely engineered structures can survive the heat, radiation and long operating life demanded by deep-space exploration.

Many NIAC ideas never become flight missions. Some still influence future technology by showing engineers what may be possible—or which problems require a different solution.

That is the value of the program.

NASA is not announcing that an interstellar generator is ready. It is funding researchers to determine whether a radically better one could be built.

For missions traveling far beyond the reach of useful sunlight, that answer could help determine how much science humanity can carry into the darkness—and how long our machines can continue speaking back to Earth.

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