Getting into the Space Nuclear Power Game with Next-Generation Technology

L3Harris Technologies has successfully finalized the design of a next-generation nuclear power source, the Next-Generation Radioisotope Thermoelectric Generator (Next Gen RTG), tailored for future NASA deep space explorations. This advancement in spacecraft power technology represents a significant milestone.

The Next Gen RTG passed its critical design review (CDR) on April 2, 2026, positioning it as a cornerstone for future missions that venture into the outer solar system.

Bill Sack, General Manager of RocketWorks and Power Systems at L3Harris, highlighted the achievement, stating, “Passing the CDR is an important milestone because it validates that our design meets all the technical requirements and can be manufactured. It also demonstrates we’ve successfully re-established this critical capability after years of limited production.”

The deployment of flight units might begin in the early 2030s, potentially powering NASA missions such as a proposed Uranus orbiter, which would rely on two Next Gen RTGs. These generators will not only provide power but will keep the orbiter’s temperature-sensitive components within operational limits in the frigid conditions of the outer solar system, underscoring the dual-purpose utility of RTGs.

Understanding the Next Gen RTG

Radioisotope Thermoelectric Generators (RTGs) work by converting heat generated from the radioactive decay of plutonium-238 into electricity. This technology is crucial for missions far from the Sun, where solar power is ineffective. RTGs have been a reliable power source for the past 60 years, with early versions still energizing NASA’s Voyager probes, launched in 1977 and now journeying through interstellar space.

The Next Gen RTG builds on the proven designs of general-purpose heat source RTGs used previously in missions like NASA’s Cassini Saturn orbiter and the New Horizons probe, which performed a Pluto flyby in 2015 and continues to explore the Kuiper Belt. Unlike the Multi-Mission RTGs installed on Mars rovers such as Curiosity and Perseverance, the Next Gen RTGs are specifically optimized for deep space operations and not for planetary surfaces.

This optimization is crucial for upcoming missions in the vacuum of space, as it allows for enhanced heat rejection and power generation in the challenging deep space conditions where the Uranus orbiter will be deployed. The Next Gen RTG promises a higher power output—approximately 250 watts at the start of its operational life—while maintaining a similar weight to the Multi-Mission RTG, ensuring reliable and long-lasting power for missions exploring the outer solar system.

“The Next Gen RTG represents a significant leap forward in efficiency,” added Sack. “We’re delivering more power in the same mass envelope, which is critical when every kilogram matters for deep space missions.”

Significance of the Next Gen RTG

The introduction of Next Gen RTGs facilitates a range of ambitious NASA missions long desired by the agency. In addition to the Uranus orbiter, these systems could support:

• Extended missions to Neptune and its moon, Triton
• Exploration of Kuiper Belt objects beyond the reach of the New Horizons spacecraft
• Long-duration missions targeting the outer planets’ moons
• Interstellar precursor missions that will extend the boundaries of exploration further than Voyager 1 and 2

Re-establishing Production

In 2021, the U.S. Department of Energy’s Idaho National Laboratory selected L3Harris to revive crucial technologies from the legacy RTG systems and modernize the design to meet the renewed interest in deep space missions. The contract is scheduled to conclude in 2027, with a production readiness review to confirm the feasibility of the next-generation system using re-established materials and components.

Leo Gard, Space Propulsion & Power Systems Program Manager at L3Harris, noted, “We are proving we can do it again. While we didn’t build the original generators, we’ve successfully reconstructed incomplete documentation and identified modern equivalents for obsolete components through creative problem-solving.”

A Collaborative Initiative

As the prime contractor for the Next Gen RTG initiative, L3Harris oversees the main structure and overall system integration. Teledyne Energy Systems Inc. of Hunt Valley, Maryland, is responsible for manufacturing the thermoelectric couples that convert heat to electricity, while BAE Systems Space and Mission Systems based in Boulder, Colorado, handles the insulation.

About Idaho National Laboratory

Battelle Energy Alliance manages Idaho National Laboratory for the U.S. Department of Energy’s Office of Nuclear Energy. INL stands as the nation’s center for nuclear energy research and development and conducts research across DOE’s strategic goal areas encompassing energy, national security, science, and the environment.

Source: L3Harris (2026-05-14)