NASA's SR-1 Freedom Nuclear Spacecraft Set to Launch Ingenuity-Style Helicopters to Mars by Late 2028

The U.S. is preparing to launch its first nuclear-powered interplanetary spacecraft, a mission NASA says will mark a major step toward extending human exploration deeper into the solar system while delivering a new fleet of robotic helicopters to the surface of Mars.

The mission, called Space Reactor-1 Freedom, or SR-1 Freedom, is targeting a launch in December 2028. NASA describes it as humanity's first fission-powered interplanetary spacecraft, designed to demonstrate nuclear electric propulsion in deep space for the first time.

What the mission will do

SR-1 Freedom will use a nuclear fission reactor to generate electricity that powers the spacecraft's electric thrusters, an approach NASA says is far more efficient for long-duration missions than traditional chemical propulsion. According to NASA's Program Executive of Fission Surface Power, Steve Sinacore, the reactor is expected to power on within 48 hours of launch and will take approximately one year to reach Mars.

The reactor itself will generate roughly 20 kilowatts of electricity using high-assay low-enriched uranium fuel, with heat transferred through a system of heat pipes and a boron carbide radiation shield protecting the rest of the spacecraft. An advanced closed Brayton-cycle power conversion system will convert the reactor's heat into electricity, while a lightweight composite and titanium radiator system handles heat rejection. The spacecraft's electric propulsion system is designed to operate at up to 48 kilowatts.

Much of the spacecraft's structure will rely on previously developed hardware rather than entirely new components. Central to that approach is the reuse of the Power and Propulsion Element, a system originally built for NASA's Lunar Gateway space station, which will be repurposed as part of SR-1 Freedom's design.

A pathfinder for future missions

NASA has repeatedly emphasized that SR-1 Freedom is intended as a technology demonstrator rather than a finished blueprint for future missions. Data gathered during the mission is expected to inform the development of a related project, Lunar Reactor-1, a proposed nuclear fission power system designed to provide continuous electricity for future lunar outposts during the Moon's extended periods of darkness.

NASA Administrator Jared Isaacman detailed the ambitions behind the program in a social media post announcing the mission. "NASA is building SR-1 Freedom, a nuclear electric propulsion spacecraft, launching to Mars in 2028," Isaacman wrote, adding that the mission's name was chosen to reflect "the spirit of American innovation and exploration" during what he described as the 250th year of the United States. Isaacman said the project would help deliver "America's nuclear power capabilities to space" and represents a key step toward eventual crewed missions to Mars and exploration of the outer solar system.

At a press event unveiling the mission, Isaacman framed the effort as long overdue. "After decades of study and billions spent on concepts that have never left Earth, America will finally get underway on nuclear power in space," he said.

The SkyFall payload

Alongside its propulsion demonstration, SR-1 Freedom will carry the SkyFall payload to Mars: three new-generation robotic helicopters built on the design of NASA's Ingenuity Mars Helicopter. Once the spacecraft reaches Mars, the helicopters will be deployed via a mid-air atmospheric entry sequence rather than a traditional rover-based landing.

The SkyFall helicopters are intended to scout potential future human landing sites and investigate subsurface water ice deposits, building on the scientific groundwork laid by Ingenuity. That earlier helicopter, delivered to Mars alongside the Perseverance rover in February 2021, became the first aircraft to achieve powered, controlled flight on another planet. Over nearly three years of operation, the roughly 1.8-kilogram helicopter completed 72 flights before being damaged and grounded in early 2024, far surpassing its original mission expectations. NASA has said Ingenuity's development cost was approximately $80 million, and the agency has credited the helicopter with opening an entirely new approach to planetary exploration.

Cost and program partnership

NASA has estimated the overall cost of building and launching SR-1 Freedom at roughly $2.1 billion, though the agency has not disclosed a detailed cost breakdown, and the mission was notably absent from NASA's fiscal year 2027 budget request released shortly after the program's initial announcement. SR-1 Freedom is being developed jointly by NASA and the U.S. Department of Energy, which oversees the nation's nuclear stockpile and is contributing expertise on reactor technology.

NASA officials have described the agency's approach to the project as intentionally conservative on new development, aiming to reuse existing hardware wherever possible to reduce cost and risk. "We're trying to leverage as much as we can with as little new development as possible," one NASA official said regarding the mission's engineering approach, acknowledging that the strategy is easier described than executed.

Part of a broader nuclear space strategy

SR-1 Freedom is one piece of a larger push by NASA to bring nuclear power into future exploration efforts, alongside plans for a nuclear reactor intended to land on the lunar surface by 2030 to help power a future outpost there. Officials have said that if SR-1 Freedom proves successful, later reactors could scale up from tens of kilowatts of power to eventually reach the megawatt range, enabling higher-power missions to the Moon and eventual crewed missions to Mars.

With roughly two years remaining before its targeted December 2028 launch, SR-1 Freedom's final spacecraft design remains a work in progress, and NASA has said it plans to seek input from commercial space companies as development continues. Whether NASA continues operating the spacecraft after it deploys the SkyFall helicopters at Mars also remains undecided, with officials suggesting the vehicle could potentially be redirected for further exploration once its primary mission is complete.