NASA has an update on its seminal deep-space exploration project of 2023—that of developing a nuclear power source. Following promising results in the Phase 1 of the project, the researchers are now aiming to boost power generation while reducing size and weight of the power source.
Last year, NASA approved a project led by the Rochester Institute of Technology aimed at creating a nuclear power source significantly smaller than those currently used in planetary missions. While many satellites rely on solar panels to convert sunlight into electricity, these panels are less effective in deep space or harsh conditions, such as Martian dust storms or lunar nights. In such scenarios, a compact nuclear power source could provide the necessary energy.
A radioisotope thermoelectric generator (RTG), also known as a radioisotope power system (RPS), is a nuclear battery that converts the heat produced by the decay of a radioactive material into electricity. Unlike traditional generators, RTGs have no moving parts, making them highly reliable and suitable for use in remote and challenging environments for long periods without the risk of mechanical failure.
What was Phase 1?
The researchers aimed to demonstrate a groundbreaking power source for outer planet missions using a new thermal power conversion method called the thermoradiative cell (TRC). By harnessing heat from a radioisotope, the TRC promises a significant increase in power density and a drastic reduction in size compared to conventional radioisotope generators. This technology opens up possibilities for smaller, more versatile spacecraft that have high power needs not met by traditional solar panels or bulky generators.
The study focused on the thermodynamics and practicality of developing this radioisotope-powered TRC, emphasizing its compactness and efficiency. The growth of key materials like InAsSb or InPSb was also assessed using metalorganic vapor phase epitaxy. Additionally, the researchers examined how TRC technology could be used to power cubesats accompanying a flagship mission to Uranus.
Phase I demonstrated the potential for generating 8 watts of electrical power from a 62.5 watt Pu-238 pellet using a TRC with specific characteristics.
What does Phase 2 aim for?
The researchers are now looking to improve upon the Phase I results by exploring the use of low-bandgap III-V materials like InAsSb in nanostructured arrays, which could significantly boost power generation while reducing size and weight compared to traditional RTGs. This advancement could enable smaller spacecraft with higher power demands, particularly for missions to distant planets and areas with little sunlight, such as polar lunar craters.
The study will now delve into the thermodynamics and feasibility of developing a radioisotope-powered TRC, with a focus on reducing system size, weight, and power consumption. The researchers plan to conduct experiments to grow materials and TRC devices, exploring new types of metal-semiconductor contacts that can withstand high temperatures.
Additionally, the original goal of Phase 1—analyzing the potential of using a radioisotope thermoradiative converter for a cubesat mission to Uranus—will be worked upon in Phase 2, which would involve a collaboration with NASA Glenn Research Center’s Compass engineering team to integrate the technology into spacecraft design. Finally, a roadmap for the development of TRC components for future missions will also be outlined.
The potential practicality of this new technology suggests exciting possibilities for future missions to destinations like Jupiter and beyond, as well as to the shadowed craters of the moon’s polar regions. With spacecraft as small as CubeSats equipped with compact generators, these missions could have all the power they need.
For instance, a flagship mission to Uranus could be complemented by a fleet of CubeSats. These smaller spacecraft could offer multiple perspectives on exploration tasks or serve as communication relays for atmospheric probes, enhancing our understanding of the outer planets.
