NASA and other space agencies are planning manned missions to the moon, Mars, Venus and other distant objects, which requires powerful and reliable power systems to power spacecraft and reduce flight time. Radioisotope energy systems (RPS), which are used by NASA over 60 years in such missions, like the Curiosity rover, Perseverance and the upcoming Dragonfly mission to Titan, is a key decision. However, the shortage of the traditional plutonium-238 isotope, caused by the cessation of its production after the Cold War, forced NASA to look for alternatives.
Americium-241 as a new energy base
Thermal Energy Conversion Division of the Glenn Space Research Center (NASA Glenn) in collaboration with the University of Leicester (Great Britain) is investigating americium-241 as an alternative heat source for RPS. This isotope, which generates heat through slow radioactive decay, can provide energy for long-duration missions beyond the Earth-Moon system. The cooperation agreement was signed in January 2025 year, and since then, teams have been testing a stand with a Stirling generator, which is powered by two electrically heated americium-241 simulators.
University of Leicester, which already 15 years is a leader in the development of RPS based on Americium, provided the heat simulators and the generator case, while NASA Glenn provided the test station, Stirling hardware and support equipment. Hannah Sargent, researcher at the University of Leicester, noted, that the special feature of this stand is its ability to work even with the failure of one Stirling converter without loss of electricity, which was successfully demonstrated during tests. This confirms the reliability of American RPS for future missions, which can last for decades.
Test results and prospects
The tests showed, that the American RPS is meeting performance and efficiency targets, which makes it promising for powering space vehicles. Stirling system, which converts heat into electricity, is compact and efficient, which is critical for mass and energy constrained missions.
The next step for NASA Glenn is to create a lighter and more accurate version of the environmental test stand, which will simulate the conditions of space. This will make it possible to assess the system's resistance to vibrations, vacuum and temperature changes. If successful, the American RPS could become the basis for powering missions to Mars, Venus or even the moons of Jupiter and Saturn.
Chinese parallels
China is also actively developing nuclear power systems for space missions. IN 2023 In 2015, the crew of the Tiangong station conducted the first orbital testing of the Stirling thermoelectric converter. Chinese scientists have developed an analytical model to evaluate a space nuclear reactor (SNRPS) based on the Stirling engine, which supports the country's plans for manned missions to the Moon to 2030 year and Mars in the next decade. These efforts highlight the global competition to develop energy solutions for deep space.
Values for space research
Americium-241 has a longer half-life (432 years) compared to plutonium-238 (88 years), making it attractive for decade-long missions. Its use could reduce dependence on limited supplies of plutonium and open up new opportunities for solar system exploration. Example, American RPS can power probes to study the clouds of Venus, icy oceans of Europe or methane lakes of Titan, where solar energy is inefficient.
The collaboration between NASA and the University of Leicester demonstrates the importance of international partnerships in overcoming technological barriers. The success of the tests of the American RPS can change the approach to the energy supply of space missions, making them more accessible and durable.
Source: https://phys.org