NASA unveils Space Reactor-1 Freedom mission to Mars in 2028

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In a significant NASA announcement, Administrator Jared Isaacman and agency leaders outlined plans for a nuclear-powered mission to Mars within the next two years.

The project involves reallocating existing Lunar Gateway hardware to demonstrate highly efficient mass transport in space, with the spacecraft carrying multiple Ingenuity-class helicopters to explore the Red Planet.

The mission, called Space Reactor-1 Freedom (SR-1 Freedom), is set to launch in December 2028.

This mission aims to showcase the use of nuclear fission in space to power electric thrusters. While nuclear technology has been around for decades, it lacked the drive, purpose, destination, and leadership—until now.

NASA’s Program Executive of Fission Surface Power, Steve Sinacore, summarized the objectives clearly: demonstrate Nuclear Electric Propulsion.

NASA plans to launch during the upcoming Mars transfer window, utilizing existing hardware for cost and schedule savings, conducting Mars-relevant science, transmitting stunning footage back to Earth, and preparing for future high-power, long-duration missions.

Importantly, this will be the first-ever nuclear-propelled spacecraft to exit Earth’s sphere of influence.

How SR-1 Freedom Works:

The spacecraft features a 20-plus kilowatt fission reactor fueled by High-Assay Low-Enriched Uranium and Uranium Dioxide, encased in a Boron Carbide Radiation Shield.
Next to it is the advanced closed Brayton cycle power conversion system—a high-efficiency, closed-loop heat engine that converts thermal energy from the reactor into electrical power for the thrusters.

SR-1 Freedom will use nuclear electric propulsion (NEP), not nuclear thermal propulsion (NTP). The reactor will solely generate electricity to power xenon ion thrusters.

This setup differs from the NERVA engine program of the 1960s, which used super-cold liquid hydrogen fed into a super-hot reactor core to produce a hot, fast gas for thrust.
The ion thrusters and power systems will come from repurposed Lunar Gateway hardware. The Power and Propulsion Element (PPE)—initially designed as the lunar space station’s power and communication hub—is now being redirected to Mars.

This module already exists and has been powered up. It’s not the first time PPE has been repurposed; it was previously developed as the bus for the now-canceled Asteroid Redirect Vehicle.
Concept of Operations (CONOPS):

After launch into an Earth-escape trajectory, the spacecraft will deploy its solar arrays within hours. Though it switches to nuclear-electric propulsion, the PPE’s solar panels will generate electricity when the reactor isn’t active.

Less than 48 hours post-launch, the fission reactor will be activated, allowing the ion thrusters to fire using nuclear power. About a year after launch, SR-1 Freedom will arrive near Mars.
A key science payload, named Skyfall, draws inspiration from Ingenuity, which was designed for five flights but completed 72 over three years. Three Ingenuity-class helicopters will be carried aboard the spacecraft.

These helicopters will be deployed mid-air after atmospheric entry, landing themselves rather than relying on a sky-crane system like previous Mars rovers.

Once on the surface, they will explore potential future human landing sites, equipped with ground-penetrating radar to map subsurface water—crucial for in-situ resource utilization to support future Mars bases.
NASA is also considering additional student-led scientific payloads for the mission.

Timeline and Readiness:

The development timeline is aggressive, starting in just three months, with major design and hardware development beginning by June. Systems must be built and ready for assembly, integration, and testing by January 2028. The full vehicle is scheduled to arrive at the launch site by October 2028, ahead of the December launch.

The launch vehicle is not yet confirmed, but the PPE previously had a contract for launch aboard a fully expendable SpaceX Falcon Heavy from 39A, alongside the Habitation and Logistics Outpost module.
Falcon Heavy can deliver 16,800 kilograms to Mars; with PPE’s roughly 5,000-kilogram mass, there’s ample room for the reactor, systems, and payloads.

Looking Ahead:

NASA stresses that Space Reactor-1 Freedom is a pathfinder, not a final blueprint. Its technology demonstrations will guide future missions, like Lunar Reactor-1, adapted for lunar conditions. Input from commercial providers will be sought as early as June.

In the 2030s, reactors could grow from tens of kilowatts to hundreds, and eventually to megawatt-scale systems, enabling higher-power missions to the Moon and crewed Mars missions.

Achieving these goals hinges on the success of Space Reactor-1 Freedom, which will be a critical first step.

This announcement was made during NASA’s Ignition event, which also outlined broader strategic adjustments to make Artemis and post-International Space Station operations more feasible under Isaacman’s leadership.

Lead image render: NASA

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