For Japanese readers, the word "tritium" likely first brings to mind the treated water from the Fukushima Daiichi nuclear plant. This radioactive substance, long debated over the propriety of its ocean release, has now reportedly been carried into space on the other side of the Pacific as a power source for a satellite. At 3:10 a.m. Eastern Time on July 7, 2026, the satellite "BOHR," developed by Miami-based City Labs, was reportedly launched aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base. What it carries is not a fission reactor but a battery called "NanoTritium," which converts the energy from the natural decay of tritium into electricity. This launch also serves as the starting gun for a nuclear battery development race that has begun between the United States and China.
Not a Fission Reactor. A Mechanism Where Tritium's Decay Becomes Electricity Directly
The name BOHR reportedly stands for "Betavoltaic Orbital High-Reliability." When one hears "nuclear power," a fission reactor tends to come to mind, but the power generation principle of the NanoTritium battery carried by BOHR is something else entirely. A fission reactor artificially splits atomic nuclei such as uranium and converts the heat generated by the resulting chain reaction into electricity. NanoTritium instead directly extracts, via a semiconductor, the electric current from the beta rays (electrons) released when tritium (hydrogen-3) undergoes natural decay.
Specifically, the emitted beta rays strike the p-n junction of the semiconductor, creating electron-hole pairs, which are then separated by the electric field inside the p-n junction, causing current to flow into an external circuit. Whereas a solar cell triggers this reaction with photons, in NanoTritium it is beta particles that play that role. Although the basic structure of the mechanism is the same, whether the process depends on daytime or the presence of sunlight differs depending on whether the energy source is sunlight or radioactive decay.
This method has no moving parts and no liquid electrolyte. According to City Labs' technical materials, the absence of moving parts and liquid electrolyte reduces fire risk to zero and allows stable power generation to continue over long periods. The characteristic of having few points of failure is a major advantage for satellites, which cannot be repaired in space. Indeed, the tritium payload carried by BOHR is expected to remain in orbit for roughly ten years. That said, test results that can confirm actual performance are expected to become available within weeks to months after launch.
Space Nuclear Policy That Took Six Years to Move, and the FAA's First Commercial Authorization
On August 20, 2019, the Trump administration issued "National Security Presidential Memorandum 20 (NSPM-20)," which granted the Secretary of Transportation (with the FAA handling the practical work) the authority to authorize launches carrying space nuclear systems. Under this framework, the FAA is reported to have issued its first-ever payload authorization for a commercial space mission for BOHR, with the authorization date reportedly being September 30, 2025. This authorization date is based on reporting from a Florida local newspaper, and has not been corroborated by multiple independent sources. Six years after NSPM-20 was issued, the first commercial case has finally reached an actual launch.
The safety analysis is said to have been conducted by City Labs, with independent verification performed by Sandia National Laboratories. However, this information also relies on the same news lineage, and no independent follow-up reporting has been confirmed. Peter Cabauy, CEO of City Labs, told the local newspaper, "This will be the world's first commercial nuclear launch." With this authorization now having led to an actual launch, NSPM-20 has advanced from a paper framework to a regulatory procedure with an operational track record.
This case, in which NSPM-20 was actually applied to a commercial mission, becomes a precedent that other companies can reference. Now that the authorization framework has been set in motion once, companies planning similar space nuclear payloads no longer need to build a regulatory-compliance path from scratch. The fact that the United States has gotten a head start in establishing practical procedures in this field becomes regulatory groundwork that will influence which side—the U.S. or China, discussed below in the context of the competition with Betavolt—accumulates a commercialization track record first.
Tritium vs. Nickel-63: The US and China Diverge in Their Choice of Isotope for Nuclear Batteries
City Labs is not the only company advancing the practical application of betavoltaic batteries. China's Betavolt, founded in 2021, has commercialized a betavoltaic battery called "BV100" that uses nickel-63, publishing specifications of 100 microwatts of output and a 50-year lifespan. The company had announced plans to release a 1-watt version in 2025. Whereas City Labs' NanoTritium uses tritium, Betavolt uses the radioactive isotope nickel-63. Even within the same betavoltaic approach, the choice of isotope has led development lineages in the U.S. and China to diverge.
An industry trade media outlet reports that City Labs is the only U.S. company holding a general license from the U.S. Nuclear Regulatory Commission (NRC) for the manufacture and sale of commercial tritium betavoltaic batteries. However, this claim is corroborated by only that single media outlet. On the regulatory front as well, the outcomes for the U.S. and China have diverged. With the "world's first" branding in hand, City Labs is positioned to gain momentum in securing contracts with DARPA (Defense Advanced Research Projects Agency), NASA, and the Air Force Research Laboratory, and Sandia National Laboratories, which handled the verification, also builds up a technical track record in the process.
For ride-share launch operators like SpaceX and Exolaunch, this becomes the seed of new demand for small nuclear-powered satellites. Meanwhile, China's Betavolt and other early movers effectively lose the record of "first commercial FAA authorization" to the U.S. side, losing one yardstick of external advantage. The plutonium-based RTG supply chain also finds itself in a relatively weaker position amid the rise of a low-cost alternative technology. It could be said that the starting gun for this development race went off not at the moment the satellite flew, but at the moment the regulatory track record was updated.
The Difference from the RTG That Powered Voyager Determines the Odds for Nuclear-Powered Satellites
The idea of using nuclear power as an energy source is nothing new. Deep-space probes, starting with NASA's Voyager, have used radioisotope thermoelectric generators (RTGs) as their power source for decades. An RTG is a system that converts the decay heat of plutonium-238 into electricity via thermoelectric conversion elements, offering the advantage of stable output even in deep space where sunlight does not reach. However, plutonium-238 is a scarce fuel with limited production, and RTG manufacturing costs have remained persistently high. The betavoltaic approach is positioned as a compact, low-cost alternative to this high-cost structure.
In 2024, City Labs was selected for NASA's Innovative Advanced Concepts (NIAC) program, proposing the application of tritium batteries to sensors that detect water and volatile substances in permanently shadowed craters on the Moon. Permanently shadowed lunar craters receive no sunlight, making conventional solar cells unusable. Extending from this, some reports have suggested that BOHR is positioned as a pathfinder demonstrating sunlight-independent lunar surface power sources for NASA's Artemis program. However, this information comes from a single article, and no official statement from NASA has been confirmed.
If this positioning is accurate, it raises the possibility that betavoltaic batteries could take over, at lower cost, part of the role RTGs have played as power sources for deep-space probes. For long-life satellites and lunar exploration vehicles, having a power source technology with fewer fuel-procurement constraints expands the range of options available. If the options for power sources that are unaffected by the presence or absence of sunlight increase, room may also open up to reconsider the very design of exploration vehicles.
NanoTritium's Wattage Output Will Be the First Answer Checked
City Labs' technical materials describe NanoTritium's output only as "very low power," without disclosing specific wattage figures. The company secured a $1.5 million contract (approximately ¥243 million, at ¥161.87/USD) jointly with Microlink Devices from DARPA's "Rads to Watts" program, aiming to eventually develop watt-class radionuclide power cells—though this is a separate research contract from the unit carried aboard BOHR. There is currently no material available to judge how close BOHR's actual output comes to this target figure.
BOHR is reported to have launched aboard SpaceX's Falcon 9 rocket as part of the Transporter-17 rideshare mission, alongside 81 other payloads, but SpaceX's official payload list does not explicitly name City Labs or BOHR. The source of this reporting is almost entirely limited to articles from a Florida local newspaper and their reprints, and no corroboration from multiple independent sources has been obtained so far. Test results confirming on-orbit performance are expected to emerge within weeks to months after launch, and it will only be after that point that figures such as the actual wattage output, commercial pricing, and mass-production timeline become clear. Whether BOHR truly reached orbit, and if so, how many watts it actually generates—these are the two blanks that will be filled in first going forward.
For Japanese readers who have long worried about the spread of tritium amid the treated-water controversy, the fact that the same substance has been deliberately launched into orbit as a power source may seem like a kind of irony. However, the actual amount of tritium carried aboard BOHR has not been disclosed, and the premise is likely quite different from the issue of managing the massive quantities of radioactive material involved in the treated-water debate. The starting gun has certainly sounded, but what will decide the outcome is the measured output figures that will become known over the coming months.