A hybrid fission/fusion reactor could be the best way to get through the ice on Europa

Within the coming years, NASA and the European House Company (ESA) will ship two robotic missions to discover Jupiter’s icy moon Europa. These are none aside from NASA’s Europa Clipper and the ESA’s Jupiter Icy Moons Explorer (JUICE), which can launch in 2024, and 2023 (respectively). As soon as they arrive by the 2030s, they may examine Europa’s floor with a sequence of flybys to find out if its inside ocean might assist life. These would be the first astrobiology missions to an icy moon within the outer solar system, collectively referred to as “ocean worlds.”

One of many many challenges for these missions is the right way to mine via the thick icy crusts and acquire samples from the inside ocean for evaluation. In keeping with a proposal by Dr. Theresa Benyo (a physicist and the principal investigator of the lattice confinement fusion mission at NASA’s Glenn Analysis Heart), a potential answer is to make use of a particular reactor that depends on fission and fusion reactions. This proposal was chosen for Section I improvement by the NASA Revolutionary Superior Ideas (NIAC) program.

The listing of ocean worlds is lengthy and assorted, starting from Ceres within the Major Asteroid Belt, the moons of Jupiter (Callisto, Ganymede, and Europa), Saturn (Titan, Enceladus, and Dione), Neptune’s largest moon (Triton), and Pluto and different our bodies within the Kuiper Belt. These worlds are all believed to have inside oceans heated by tidal flexing resulting from gravitational interplay with their guardian physique or (within the case of Ceres and Pluto) the decay of radioactive components. Additional proof of those oceans and exercise contains floor plumes and striated options indicating exchanges between the floor and inside.

The principle problem for exploring the interiors of those worlds is the thickness of their ice sheets, which might be as much as 40 km (25 mi) deep. In Europa’s case, totally different fashions have yielded estimates of between 15 and 25 km (10 and 15 mi). As well as, the proposed probe might want to deal with hydrostatic ice with various compositions (resembling ammonia and silicate rock) at totally different depths, pressures, temperatures, and densities. It should additionally should deal with water strain, keep communications with the floor, and return samples to the floor.

NASA has explored the opportunity of utilizing a heating or boring probe to move via the icy sheet to entry the inside ocean. Particularly, researchers have proposed utilizing a nuclear-powered probe that might depend on radioactive decay to generate warmth and soften via the floor ice. Nonetheless, a staff of NASA researchers led by Dr. Benyo has proposed a brand new methodology that might depend on one thing aside from standard radioactive isotopes—plutonium-238 or enriched uranium-235. As a substitute, their methodology would contain triggering nuclear fusion reactions between the atoms of a strong metallic.

Their methodology, referred to as lattice confinement fusion, was described in two papers printed within the April 2020 situation of Bodily Evaluate C, titled “Nuclear fusion reactions in deuterated metals” and “Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals.” As Dr. Benyo defined in a latest NASA Glenn Analysis Heart press assertion:

“Scientists are desirous about fusion, as a result of it might generate monumental quantities of power with out creating long-lasting radioactive byproducts. Nonetheless, standard fusion reactions are troublesome to realize and maintain as a result of they depend on temperatures so excessive to beat the robust electrostatic repulsion between positively charged nuclei that the method has been impractical.”

Typical fusion strategies usually come right down to inertial or magnetic confinement. With inertial confinement, fuels resembling deuterium or tritium (hydrogen-2 or -3) are compressed to excessive pressures (for nanoseconds) the place fusion can happen. In magnetic confinement (tokamak reactors), the gasoline is heated till it reaches temperatures in extra of what happens on the middle of the sun—15 million °C (27 million °F)—to realize nuclear fusion. This new methodology creates fusion reactions throughout the confines of a metallic lattice loaded with deuterium gasoline at ambient temperatures.

This new methodology creates an brisk setting contained in the lattice the place particular person atoms obtain equal fusion-level kinetic energies. That is achieved by packing the lattices with deuterium at densities one billion instances larger than in tokamak reactors, the place a neutron supply accelerates deuterium atoms (deuterons) to the purpose that they collide with neighboring deuterons, inflicting fusion reactions. For his or her experiments, Dr. Benyo and her colleagues uncovered deuterons to a 2.9+MeV energetic X-ray beam, creating energetic neutrons and protons.

This course of might permit for fast-fission reactions utilizing lattices constructed from metals like depleted uranium, thorium, or erbium (Er⁶⁸) in a molten lithium matrix. The staff additionally noticed the manufacturing of extra energetic neutrons, indicating that boosted fusion reactions—aka. screened Oppenheimer-Phillips (O-P) nuclear stripping reactions—additionally happen within the course of. In keeping with Dr. Benyo, both fusion course of is scalable and may very well be a pathway to a brand new kind of nuclear-powered spacecraft:

“The ensuing hybrid fusion quick fission nuclear reactor can be smaller than a standard fission reactor the place a decrease mass energy supply is required and supply environment friendly operation with thermal waste warmth from reactor heats probe to soften via ice shelf to sub-ice oceans.”

A bonus of this new course of is the important function that metallic lattice electrons whose negative charges assist “display” positively charged deuterons. In keeping with the speculation developed by mission theoretical physicist Dr. Vladimir Pines, this screening permits adjoining deuterons to method each other extra carefully. This reduces the prospect that they may scatter whereas rising the chance that they may tunnel via the electrostatic barrier and promote fusion reactions. In keeping with NASA mission principal investigator Dr. Bruce Steinetz, there are hurdles to beat, however the mission is off to begin:

“The present findings open a brand new path for initiating fusion reactions for additional examine throughout the scientific group. Nonetheless, the response charges have to be elevated considerably to realize considerable energy ranges, which can be potential using varied response multiplication strategies into consideration.”

One of these nuclear course of may very well be a part of a Europa Lander, a proposed NASA mission that might construct on the analysis carried out by the Europa Clipper and JUICE. With extra examine and improvement, this know-how is also used to create energy techniques for long-duration exploration missions, just like NASA’s Kilopower Reactor Utilizing Stirling Expertise (KRUSTY) mission. The identical know-how might allow new engine ideas just like the Nuclear-Thermal and Nuclear-Electrical Propulsion (NTP/NEP) NASA and different space companies are investigating.

Lastly, this proposed methodology might have functions for all times right here on Earth, offering a brand new type of nuclear power and medical isotopes for nuclear drugs. As Leonard Dudzinski, the Chief Technologist for Planetary Science at NASA’s Science Mission Directorate (SMD), mentioned,

“The important thing to this discovery has been the proficient, multi-disciplinary staff that NASA Glenn assembled to analyze temperature anomalies and materials transmutations that had been noticed with extremely deuterated metals, We’ll want that method to resolve important engineering challenges earlier than a sensible utility might be designed.”