Over the next fifteen years, multiple space agencies and their commercial partners intend to mount crewed missions to the Moon and Mars. In addition to placing “footprints and flags” on these celestial bodies, there are plans to establish the infrastructure to allow for a long-term human presence. To meet these mission requirements and ensure astronaut safety, several technologies are currently being researched and developed.
At their core, these technologies are all about achieving self-sufficiency in terms of resources, materials, and energy. To ensure that these missions have all the energy they need to conduct operations, NASA is developing a Fission Surface Power (FSP) system that will provide a safe, efficient, and reliable electricity supply. In conjunction with solar cells, batteries, and fuel cells, this technology will allow for long-term missions to the Moon and Mars in the near future.
For NASA, having fission reactors for lunar surface operations is a vital part of the Artemis Program, which aims to create a program of “sustained lunar exploration.” This means infrastructure is required, like the Lunar Gateway (where spacecraft will dock and resupply) and the Artemis Base Camp on the surface, where astronauts will eat, exercise, and sleep when not conducting extravehicular activities (EVAs) – i.e., surface operations.
Artist’s impression of the Kilopower fission reactor on the Moon. Credit: NASA/JPL-Caltech
This base will require a considerable amount of electricity so astronauts can recharge rovers, conduct experiments, and produce water, propellant, building materials, and oxygen gas using the Moon’s natural resources – a process known as In-Situ Resource Utilization (ISRU). Jim Reuter is the associate administrator for NASA’s Space Technology Mission Directorate (STMD), which funds the fission surface power project.
“Plentiful energy will be key to future space exploration,” he said in a NASA press release. “I expect fission surface power systems to greatly benefit our plans for power architectures for the Moon and Mars and even drive innovation for uses here on Earth.” The concept builds on NASA’s Kilopower project, an effort to create a small, lightweight fission system that could provide up to 10 kilowatts (kW) of power continuously for at least ten years.
The project wrapped up in March 2018 with the successful completion of the Kilopower Reactor Using Stirling Tech (KRUSTY) demonstrator. This prototype consisted of a solid, cast uranium-235 reactor core (about the size of a paper towel roll) and passive sodium heat pipes that transferred the heat generated by slow fission reactions to high-efficiency Stirling engines, which convert the heat to electricity.
Based on this success, NASA has since partnered with the U.S. Department of Energy (DoE) – through the Idaho National Laboratory (INL) operated by Battelle Energy Alliance – to develop the Kilopower-inspired FSP for the Artemis Program. This will culminate with a technology demonstration, tentatively scheduled for the early 2030s, which will see a prototype reactor will be sent to the Moon to test its capabilities under lunar conditions.
Artist’s concept of a fission surface power system on Mars. Credit: NASA
As Todd Tofil, the FSP Project Manager at NASA’s Glenn Research Center, explained:
“NASA and the DOE are collaborating on this important and challenging development that, once completed, will be an incredible step towards long-term human exploration of the Moon and Mars. We’ll take advantage of the unique capabilities of the government and private industry to provide reliable, continuous power that is independent of the lunar location.”
On Nov 19th, NASA and the DoE issued a solicitation to American companies for design concepts for a fission power system that could be ready to launch within a decade for a demonstration on the Moon. As stated in solicitation documents, the FSP should consist of “a uranium-fueled reactor core, a power conversion system (PCS), a thermal management system, and a power management and distribution (PMAD) system having a capability to provide no less than 40 kilowatts of continuous electric power at the user interface at end of life.”
In conjunction with conventional methods, compact and lightweight fission reactors are considered ideal for providing electricity for lunar exploration. For starters, fission systems are reliable, capable of operating continuously in the permanently-shadowed craters that dot the Moon’s South Pole-Aitken Basin. During lunar nights (which last 14 Earth days), solar power is largely unavailable, making reactors highly desirable.
The system NASA envisions will provide at least 40 kilowatts (kW) of power, enough to continuously power 30 houses here on Earth for ten years. Thanks to how the technology has matured, nuclear power systems can also be scaled to create compact and lightweight systems. This is key to fulfilling NASA’s Artemis mission requirement for power systems capable of autonomous operation from the deck of a lunar lander or a lunar surface rover.
An artist’s conception shows a Mars transit habitat with a nuclear propulsion system. Credit: NASA
Configured thusly, a system like the FSB could provide enough power to sustain a lunar base and (in the coming decades) an outpost on Mars. On Mars, seasonal variations lead to dust storms that can sometimes grow large enough to encompass the entire planet and last for months. At times like this, solar energy is unreliable, and wind power, batteries, and fuel cells can only pick up so much of the slack.
Another bonus to this research is how it will help aid in the development of nuclear propulsion systems that rely on reactors to generate power. These include Nuclear-Thermal and Nuclear-Electric Propulsion (NTP/NEP) technologies, which could shorten travel time to Mars to just 100 days. Here too, NASA has been researching the technology for decades, with very encouraging results (e.g., the NERVA reactor).
Over the next twelve months, NASA and the DOE will select competing U.S. companies to develop initial designs. These will inform an industry solicitation for the final design and construction of flight-qualified fission power systems next year. The finalists of this phase will have their finished designs compete for a demonstration mission to the Moon. If all goes well, surface operations on the Moon and Mars will never have to worry about the lights going out.