Beyond solar power: how nuclear fission could drive humanity to Mars
For decades, NASA has relied on the sun or radioactive decay to power deep space probes. But as we look toward Mars and the outer planets, solar energy becomes impractical. Now, a new era of nuclear propulsion promises to double efficiency and transform interplanetary travel.
While NASA has successfully used radioisotope thermoelectric generators (RTGs) for decades—powering iconic missions like Voyager 1, Voyager 2, and the Perseverance rover—these systems rely on the heat from the decay of plutonium-238. These are power sources, not engines. To move massive payloads across the solar system, NASA is now developing Space Nuclear Propulsion (SNP), which uses nuclear fission to generate thrust. This technology splits into two distinct approaches: nuclear thermal and nuclear electric propulsion.
Nuclear thermal propulsion works by using a fission reactor to heat a liquid propellant, turning it into a gas that is exhausted through a nozzle. This method can provide high thrust and roughly double the propellant efficiency of traditional chemical rockets. Conversely, nuclear electric propulsion uses reactor heat to generate electricity, much like Earth-based power plants. This electricity then ionizes a gaseous propellant, such as xenon or krypton, which is electromagnetically accelerated to create thrust. This method is particularly vital for deep space, where solar power is insufficient.
The upcoming Space Reactor-1 (SR1) Freedom mission, planned for a 2028 launch to Mars, will serve as a critical demonstrator for nuclear electric propulsion. While more modest than the ambitious, cancelled Jupiter Icy Moons Orbiter (JIMO) design, SR1 Freedom represents a tangible step toward making long-term human habitation of the Moon and Mars possible. By providing high power for onboard instruments and communication, these systems will allow spacecraft to operate in the dark, dusty, and harsh environments of the outer solar system, far beyond the reach of the Sun's light.
Source: Will NASA's Nuclear Powered Spacecraft Revolutionize Space Exploration?
