As space agencies set their sights deeper into space than ever before, they’re going to need some innovative new tech to get the job done — and nuclear power might do the trick.
Nuclear energy has aided trips to the cosmos for six decades, taking our understanding of the solar system to new heights. But just how far away are these technologies from becoming humanity’s most tried and true method to power vehicles and usher in a new era of extraterrestrial exploration?
As Thomas Zurbuchen, former associate administrator for NASA's Science Mission Directorate, put it, “Nuclear power has opened the solar system to exploration … And we’re just getting started.”
Nuclear in space: It's only the beginning
In 1961, the United States Navy sent up the first space vehicle to carry a nuclear power supply. Then, in 1977 the nuclear battery-powered Voyager probes lifted off. Decades later, they’re still traveling beyond the farthest reaches of our solar system in NASA’s longest-running mission.
To date, many NASA missions, such as the Mars rovers Curiosity and Perseverance, and spacecraft like Cassini, have gotten juice from one of the simplest nuclear space technologies available: radioisotope thermoelectric generators.
Inside these lightweight power systems, plutonium batteries convert the heat given off by radioactive decay into electricity. In terms of safety, nuclear power has risks. The International Atomic Energy Agency notes that if nuclear-powered spacecraft do become the norm, they could harm both people and the environment if they fall apart during the hellish burn of re-entry or scatter radioactive debris after a crash.
But compared to other types of fuel, nuclear is incredibly reliable because it lasts longer than typical batteries and doesn’t rely on exposure to the Sun as solar energy does. Now, upcoming long-duration expeditions, such as NASA’s Dragonfly mission to Saturn’s largest moon Titan, will depend on these systems to help it trapeze around the world’s craggy surface.
Better, faster, stronger nuclear
As the next generation of astronauts prepares to embark on longer missions, nuclear systems could come in handy by offering quicker, more efficient transportation through the cosmos.
For example, they could help NASA reach its goal of returning humans to the Moon this decade and even send manned missions to Mars by the late 2030s or early 2040s. During these expeditions, nuclear tech may enable future spacecraft to carry bigger scientific payloads, bring back more samples to Earth, and slash travel times to and from deep space destinations.
It's hard to say whether nuclear breakthroughs could usher in what avid sci-fi fans call warp speed, but this research could enable faster vehicles and allow scientists to study a bigger slice of the Universe.
To this end, scientists across multiple fields are concocting the nuclear propulsion systems of the future. For example, NASA’s Innovative Advanced Concepts (NIAC) program is currently nurturing a study concept that aims to use nuclear thermal propulsion (NTP) to cut down travel time for crewed missions to Mars.
“Our goal is more to try to get quickly to the other planets,” Ryan Gosse, a hypersonics researcher at the University of Florida and leading member of the Florida Applied Research in Engineering (FLARE) team, tells Inverse. “The big issue is that we can use current technology, but it takes a long time.”
While a current trip to Mars typically takes about nine months, the design Gosse submitted would aim to cut the journey’s duration by nearly two-thirds — reducing nearly a year of lonely space travel to 45 days.
The super-speedy new spacecraft would work like a hybrid car, Gosse says. Similar to how these operate on both gas and batteries, nuclear technology would use two kinds of electric propulsion cycles. One is nuclear electric propulsion, or using electrical power derived from a reactor to accelerate a propellant, which NASA hopes to use to power many smaller probes. The other is nuclear thermal propulsion, which offers high thrust by pumping liquid propellant — typically hydrogen — through a reactor core.
These two techniques come with pros and cons, but faster NTP-powered objects could help people avoid high levels of radiation exposure by spending less time in space.
Going to the dark side
The ability to travel double-time around our cosmic neighborhood could benefit companies’ dreams of extraterrestrial settlements.
Already, private companies like Axiom Space, Blue Origin, and Orbital Assembly are looking into creating commercial space stations and space hotels to attract potential space tourists. Nuclear technologies could potentially power these space stations or trips back and forth to the Moon — but it's too early to tell to what extent, Gosse notes.
NASA recently chose Gosse’s proposal for Phase I of the NIAC program, but it’ll still be years before the project could impact NASA’s short-term nuclear plans. Regardless of the timeline, organizations around the world are interested in championing nuclear-powered space systems. For example, across the Atlantic, the U.K. Space Agency is investing in several nuclear energy projects for space exploration.
The agency is funding work on radioisotope power systems that use americium, an isotope that can be recycled from legacy nuclear fuel to create space batteries (most use plutonium).
“Opening up an alternative route for radioisotope power systems suddenly will make them available to many more actors, which in itself will open up more opportunities,” Andrew Kuh, the U.K. Space Agency’s exploration technology manager, tells Inverse.
The agency recently announced that it’s backing research by car manufacturer Rolls-Royce to design a micro-reactor capable of powering a potential lunar base.
“In the next decade, we're going to see a huge change in both the number of nuclear power systems for space and the number of missions using them.”
Nuclear could also help future astronauts explore the elusive dark side of the Moon, where they'd likely struggle to use solar-powered tools. That’s one reason why generating electricity via this micro-reactor could prove crucial for missions on the lunar surface, Kuh says. In collaboration with the U.S. Department of Energy, NASA has stated that they, too, want to plop a nuclear reactor on the Moon by the decade’s end.
For those worried about the potential for nuclear disaster out in the void, we’re still a ways away from rolling out new nuclear propulsion systems on such a large scale. Still, some optimistic scientists believe it’s only a matter of time before they’re perfected as a sustainable power option.
“It's definitely an exciting time,” Kuh says. “In the next decade, we're going to see a huge change in both the number of nuclear power systems for space and the number of missions using them.”
The Cusp is a weekly Inverse series that offers a sneak peek at the science and technology that could power our future.
