Europe’s Bid for Nuclear Energy Sovereignty in Space
Fourteen Days of Darkness
Every lunar mission faces the same constraint: the Sun disappears for fourteen days.
When it does, temperatures plunge below –170°C. Solar panels produce nothing. Batteries become dead weight. Electronics freeze. Most lunar hardware is designed to endure the night, not operate through it. If sustained presence on the Moon is the goal - rovers, resource exploration, scientific stations - then solar power alone is not enough.
Only a handful of countries have solved this problem in a meaningful way. The United States, Russia, and increasingly China have developed radioisotope power systems that convert the heat from decaying nuclear material into electricity. These systems can run for years without sunlight. They are quiet, compact, and politically sensitive. Europe does not have an equivalent capability at scale.
That is the context in which a small Latvian company, Deep Space Energy, is trying to build something ambitious.
Rethinking the Radioisotope Generator
Deep Space Energy, founded in 2022, is developing a radioisotope power system designed specifically for long-duration space missions. The company recently secured €930K in combined pre-seed funding and public grants from ESA, NATO DIANA, and the Latvian government. The funding is modest. The technical claim is not.
Traditional radioisotope thermoelectric generators (RTGs), like those used on NASA’s Mars rovers, are extremely reliable because they have no moving parts. But they are inefficient. Only a small fraction of the heat produced by the radioactive material is converted into electricity. The rest is lost.
Deep Space Energy is taking a different approach. Instead of a static thermoelectric system, it uses a modified Stirling engine, a dynamic converter that turns heat into mechanical motion and then into electricity.
In theory, Stirling-based systems can be four to five times more efficient than conventional RTGs. That means requiring significantly less radioactive fuel for the same power output. Efficiency matters because radioisotope material is scarce, expensive, and tightly controlled.
NASA itself pursued a similar concept through its Advanced Stirling Radioisotope Generator program in the 2000s. The system performed well in testing but was ultimately cancelled. The concern was not efficiency. It was reliability. Moving parts introduce risk, and deep-space missions cannot tolerate mechanical failure.
Deep Space Energy argues it has addressed that concern by simplifying the architecture to a single piston design, reducing potential failure points. The company says it has validated the system under laboratory conditions and is now working toward integration into spacecraft subsystems. A demonstration flight is planned for 2029, likely using an electric emulator rather than actual nuclear material. The goal is to build flight heritage before navigating the regulatory complexity of launching radioactive payloads.
The Fuel Question
There is another constraint that sits quietly beneath the engineering challenge: supply. There is no large-scale European production pipeline for the radioisotopes typically used in space power systems, such as plutonium-238. The United States has restarted limited production. Russia historically supplied some material. China is investing heavily in its own nuclear space infrastructure.
Europe’s position is more ambiguous. Deep Space Energy’s CEO, Mihailis Ščepanskis, has acknowledged that there is currently no dependable or scalable supply of radioisotope material. Higher efficiency reduces the amount of fuel required, but it does not eliminate the underlying dependency. If Europe intends to operate independently in deep space, power systems and fuel supply eventually have to be addressed together.
A Long Timeline
The company’s immediate focus is engineering development and team expansion. The newly secured funding supports that stage, not full flight qualification or nuclear deployment. Operational missions are projected for the early 2030s, pending regulatory approval and institutional demand. Ščepanskis envisions a lunar surface populated by small, autonomous rovers by 2035, capable of surviving the lunar night without relying on sunlight. That vision assumes technical success, regulatory clearance, and a broader ecosystem willing to fund and deploy nuclear-powered systems beyond Earth orbit.
For now, Deep Space Energy remains an early-stage effort. But it is attempting to tackle one of the hardest constraints in sustained lunar operations: baseload power in a place where the Sun disappears for half the month. In space, energy is persistence. And persistence is presence.