New fuel for nuclear power systems could enable missions to Mars and beyond

by Matthew Williams, Universe Today

Beyond plans to return astronauts to the moon for the first time since the Apollo Era, NASA and other space agencies have their sights trained on Mars, Venus, and other deep-space destinations. To accomplish this, robust power systems are needed to provide ample power for spacecraft instruments and propulsion systems, thus reducing overall transit times.

To this end, NASA is considering Radioisotope Power Systems (RPS), which have been used by the agency for over 60 years, most recently with the Curiosity and Perseverance rovers on Mars and the upcoming Dragonfly mission destined for Titan.

Historically, RPSs have relied on plutonium-238 as a heat source, which generates heat through slow radioactive decay. However, NASA is facing a potential shortage of this isotope, given that the U.S. Department of Energy (DoE) ceased production after the Cold War and stockpiles are dwindling. To address this, the Thermal Energy Conversion Branch at NASA's Glenn Research Center and the University of Leicester have partnered to investigate Americium-241 as an alternative. This element could be an additional RPS heat source, powering future long-duration missions to destinations far beyond the Earth-moon system.

For more than 15 years, researchers at the University of Leicester have been leaders in the development of Americium-RPS and heater units. Since the agreement was reached back in January, these researchers have been working with NASA scientists to evaluate the capabilities of a Stirling generator testbed powered by two electrically heated Americium-241 simulators. The University of Leicester provided the heat simulators and generator housing, while the Stirling Research Lab at NASA Glenn provided the test station, the Stirling hardware, and support equipment.

Hannah Sargeant, a research fellow at the University of Leicester, said, "A particular highlight of this (testbed) design is that it is capable of withstanding a failed Stirling convertor without a loss of electrical power. This feature was demonstrated successfully in the test campaign and highlights the robustness and reliability of an Americium-Radioisotope Stirling Generator for potential future spaceflight missions, including long-duration missions that could operate for many decades."

These tests achieved their performance and efficiency target, thereby demonstrating that an Americium-fueled RPS could be a viable power source for future missions. China also plans to send crewed missions to the moon by 2030 and Mars sometime in the next decade. To this end, they are also pursuing Stirling engines for nuclear power systems to meet the energy needs of long-duration missions.

This progress in alternative power sources for deep-space missions represents a significant advancement in space exploration capabilities. The next steps involve rigorous testing and refinement of the technologies, ensuring that they can meet the demands of prolonged space missions.

Key Highlights

• Power Systems Evolution: Transitioning from plutonium-238 to Americium-241 heat sources.
• First Tests: Achieving performance and efficiency targets with Stirling generators.
• Global Efforts: Recognition of similar pursuits by China in nuclear propulsion technologies.
• Future Prospects: Continued collaboration between NASA and academic institutions for ongoing development.