NASA’s Space Reactor-1 Freedom mission, scheduled for launch in late 2028, will be the first nuclear-powered interplanetary spacecraft, carrying a working fission reactor to test nuclear electric propulsion and deploying three Ingenuity-style helicopters near Mars in 2029.

This pathfinder mission is designed to establish nuclear propulsion capability in deep space while simultaneously advancing aerial exploration of the Martian surface.

NASA plans to send SR-1 Freedom, a spacecraft carrying a nuclear reactor, towards Mars in late 2028. The mission is unusual because it integrates nuclear fission power directly into a propulsion system rather than simply carrying a reactor as a passive experiment.

Freedom will not land on Mars but will perform a flyby in 2029, during which it will release SkyFall, a payload containing three helicopters derived from the Ingenuity design. These aircraft will survey the Martian environment, measure weather conditions, and use ground-penetrating radar to search for subsurface ice.

The SR-1 Freedom reactor operates on high-assay low-enriched uranium fuel. It uses a closed Brayton cycle power-conversion system capable of producing 20 kilowatts of electricity.

The spacecraft’s power and propulsion element is designed to generate 48 kilowatts of electrical power, supporting a propulsion system that includes Hall-effect thrusters rated at 12 kilowatts.

This integration demonstrates how nuclear-generated electricity can sustain propulsion in deep space, where solar power becomes less effective. The mission is intended to provide flight heritage for nuclear hardware, establish regulatory precedent, and build the industrial base for future fission power systems.

Freedom’s design draws on earlier work at NASA’s Glenn Research Center in Cleveland, where engineers repurposed hardware from the Lunar Gateway program. Heat pipes developed during the Kilopower experiment in 2018 are being used to transfer reactor heat to the engines.

This approach reduces mass by eliminating the need for water-based steam systems, making the spacecraft more efficient for deep-space travel. The mission is expected to mark the first time a nuclear fission reactor is used to power propulsion beyond Earth orbit.

The SkyFall payload will release three helicopters based on Ingenuity, which achieved the first powered flight on another planet in 2021.

These aircraft will carry imaging equipment, ground-penetrating radar, and sensors to measure air temperature, wind speed, and direction. Their radar observations could help locate subsurface ice deposits, which are critical for future human exploration.

Flying on Mars is challenging due to its thin atmosphere, but the helicopters are designed to operate for months or even years, depending on mission performance. Their aerial perspective will allow scientists to study terrain and dust movement more effectively than ground-based rovers.

Freedom is also linked to future lunar exploration. Lessons from SR-1 will inform Lunar Reactor-1, a planned fission surface power system designed to provide up to 40 kilowatts of electricity for a Moon base, including during periods of darkness.

By testing nuclear propulsion in flight first, NASA reduces risk before attempting to operate reactors on planetary surfaces. This mission is therefore a stepping stone towards sustainable power for both lunar and Martian exploration.

The United States has prior experience with nuclear power in space, notably the SNAP-10A reactor launched in 1965, which produced 600 watts of electricity before its mission ended after 43 days. Freedom builds on that legacy by using nuclear-generated electricity for propulsion, a far more ambitious application.

If successful, the mission will demonstrate how nuclear propulsion can support efficient transport in deep space, enabling exploration of regions beyond Jupiter where solar arrays are ineffective.

Freedom’s Mars flyby and SkyFall deployment will test new methods of exploring the Martian surface while simultaneously advancing nuclear propulsion technology. The mission is expected to establish the foundation for future spacecraft capable of supporting human exploration of the Moon, Mars, and the outer Solar System.

Agencies