Key Takeaways
- City Labs successfully launched the BOHR cubesat on July 7, 2024, marking the first commercial in‑orbit demonstration of a tritium‑based betavoltaic power system.
- The NanoTritium device converts the low‑energy electrons from tritium decay into microwatts of electricity, enough to power sensors and low‑draw electronics for years without sunlight.
- Although the spacecraft still relies on conventional solar arrays for bus operations, the betavoltaic unit independently powers the mission’s payload, proving the concept of a hybrid power architecture.
- The launch was cleared under the FAA’s new regulatory framework (National Security Presidential Memorandum‑20), representing the first commercial nuclear mission to use that process.
- Funding came from a mix of private investment, Pentagon Operational Energy Innovation Directorate contracts, and SBIR awards from AFRL, AFWERX, NASA, and SpaceWERX.
- City Labs plans a 2027 flight of a tritium‑powered Radioisotope Heater Unit (RHU) to provide heat during lunar night, followed by operational systems for long‑duration lunar surface missions.
- Successful betavoltaic and RHU technologies could extend mission lifetimes in deep space, permanently shadowed regions, and other environments where solar power is impractical.
Overview of the BOHR Mission
City Labs announced that its BOHR (Betavoltaic Orbital High‑Reliability) cubesat lifted off on July 7, 2024, aboard SpaceX’s Transporter‑17 rideshare mission. The launch placed the small satellite into low‑Earth orbit, where it began an on‑orbit test of the company’s NanoTritium betavoltaic power source. The primary goal of the demonstration is to verify that the tritium‑based device can generate electricity continuously, independent of sunlight, over extended periods. Success would open new possibilities for spacecraft that must operate in dark or low‑light environments, such as the lunar poles or deep‑space probes far from the Sun. While the BOHR spacecraft itself still uses traditional solar arrays to run its bus—attitude control, communications, and onboard computer—the NanoTritium unit is dedicated solely to powering the experimental payload. This hybrid approach allows engineers to isolate the performance of the betavoltaic system without jeopardizing the spacecraft’s core functions.
Betavoltaic Technology Explained
The NanoTritium system relies on betavoltaics, a direct‑energy conversion process that captures the kinetic energy of beta particles (high‑speed electrons) emitted during radioactive decay. Tritium, a weakly radioactive isotope of hydrogen, releases low‑energy electrons as it decays into helium‑3. City Labs’ design surrounds a tritium source with a semiconductor layer that absorbs these electrons and converts their energy into a steady electric current. Because tritium’s beta particles are relatively low‑energy, the resulting power output is modest—typically in the microwatt range—far below what is needed to run a satellite’s main systems but sufficient for low‑power sensors, timers, memory chips, or communication beacons that must operate continuously for years. The technology’s chief advantage is its longevity: tritium has a half‑life of about 12.3 years, providing a predictable, decay‑driven power source that does not degrade with temperature cycles or suffer from the limited charge‑discharge life of conventional batteries.
Regulatory Approval and Safety
The BOHR launch represents a milestone in spaceflight regulation: it is the first commercial nuclear mission to obtain clearance under the Federal Aviation Administration’s launch approval process established by National Security Presidential Memorandum‑20 (NSPM‑20). NSPM‑20 created a streamlined pathway for licensing spacecraft that carry radioactive materials, balancing the need for innovation with safety and security considerations. City Labs emphasized that its tritium‑based devices emit only low levels of radiation, well within limits that pose minimal risk to launch personnel, the public, or the space environment. The company engineered the NanoTritium units for robust containment, ensuring that the tritium cannot be released under normal handling, transportation, or integration scenarios. By demonstrating compliance with these safety standards, City Labs hopes to pave the way for broader adoption of betavoltaic and other radioisotope power systems in the commercial sector.
Funding and Partnerships
Development of the BOHR demonstrator benefited from a blend of a layered funding strategy. Private investment provided the core capital for City Labs’ research and hardware fabrication. Additional support arrived from the U.S. Department of Defense’s Operational Energy Innovation Directorate, specifically through its Operational Energy Capability Improvement Fund, which seeks technologies that can extend the endurance of forward‑deployed sensors and communications nodes. The project also secured multiple Small Business Innovation Research (SBIR) contracts: awards from the Air Force Research Laboratory (AFRL), AFWERX (the Air Force’s technology‑acceleration arm), NASA, and SpaceWERX (the Space Force’s innovation hub). These partnerships not only supplied financial resources but also offered technical expertise, testing facilities, and pathways toward potential future procurement by government agencies.
Future Plans: Tritium RHU and Lunar Applications
Looking beyond the betavoltaic demonstration, City Labs intends to flight‑test a tritium‑powered Radioisotope Heater Unit (RHU) in 2027. Unlike the NanoTritium system, which generates electricity, an RHU produces heat through the same radioactive decay process. Such heaters are essential for keeping spacecraft components, batteries, and scientific instruments from freezing during prolonged periods without sunlight—most notably the approximately two‑week lunar night or within permanently shadowed craters near the moon’s poles. Historically, NASA has relied on plutonium‑238‑fueled RHUs for missions like the Voyager probes and the Mars Science Laboratory. By substituting tritium for plutonium, City Labs aims to offer a commercially viable, lower‑regulatory‑burden alternative that still delivers reliable thermal management. Successful validation of the RHU could enable long‑duration lunar surface operations, support habitats, and empower autonomous sensor networks that must survive the harsh thermal swings of the Moon.
Broader Implications for Space Power
The successful orbital test of a commercial betavoltaic power source underscores a growing diversification of space‑energy options beyond solar panels and conventional chemical batteries. For missions where sunlight is intermittent, weak, or unavailable—such as outer‑planet explorers, Europa landers, or far‑side lunar observatories—having a compact, long‑life power source can dramatically increase mission flexibility and reduce reliance on large, deployable solar arrays or limited‑capacity batteries. Moreover, the ability to pair betavoltaic units with solar arrays in a hybrid architecture offers designers a way to baseline critical subsystems (e.g., flight computers, radios) on a steady power trickle while using solar energy for peak‑demand activities. As regulatory frameworks mature and safety data accumulate, we may see an increase in private‑sector investment in microscale nuclear power, fostering new business models for persistent space‑based services such as space‑based Internet of Things nodes, orbital debris monitoring, or in‑orbit manufacturing.
Conclusion
City Labs’ BOHR mission marks a tangible step toward operationalizing betavoltaic technology in space. By proving that a tritium‑based system can generate reliable microwatt‑level power in orbit, the company has demonstrated a viable path for powering low‑draw electronics in environments where solar energy is unreliable. The successful navigation of the FAA’s NSPM‑20 licensing process further validates that commercial nuclear payloads can be launched safely and responsibly. With planned advances toward a tritium RHU and eventual operational systems for lunar and deep‑space applications, City Labs is helping to expand the toolkit available to spacecraft designers, potentially enabling longer, more resilient missions across the solar system. Continued collaboration between private innovators, defense agencies, and civilian space organizations will be crucial to harnessing these emerging power technologies for the next era of exploration and utilization.