The U.S. National Aeronautics and Space Administration (NASA) has confirmed a major initiative led by Administrator Jared Isaacman this week: to build a nuclear-powered spacecraft destined for Mars, with a total project cost exceeding $2 billion.
This new cost estimate for the mission, named "Space Reactor One • Freedom," comes as NASA is concurrently advancing several other flagship programs, including the crewed return to the Moon and the construction of a lunar outpost, while its overall budget is expected to remain stable.
In a statement, NASA said: "The initial total cost estimate for the project is approximately $2.1 billion. This figure will be continuously refined and updated through the subsequent procurement process."
A document submitted to Congress outlines NASA's planned annual funding for the project: $640 million in fiscal year 2026, $890 million in FY 2027, $415 million in FY 2028, and $180 million in FY 2029. The funds will be drawn from the agency's deep space exploration account and a special appropriation approved through last year's bipartisan reconciliation bill.
However, the document clarifies that this cost estimate does not include funding for the "Celestial Fall" science investigation payload, which the nuclear-powered spacecraft will deliver to Mars. NASA has not disclosed the cost of the Celestial Fall project, with Mars research scientists warning it could strain the agency's overall science exploration budget.
Since announcing this new Mars mission in March, NASA has revealed few details about the spacecraft. Notably, the agency's budget request for fiscal year 2027, released one week after the mission announcement, contained no dedicated funding for this project.
Scheduled for launch in late 2028, the mission will represent humanity's first in-space demonstration of nuclear electric propulsion technology. The spacecraft will deploy three uncrewed helicopters to Mars to collect scientific data and scout for potential water resources.
Agency officials stated that to accelerate development, the spacecraft's construction will heavily utilize existing, proven hardware. The power and propulsion element originally designed for the lunar Gateway space station will be repurposed as the core of this Mars spacecraft; NASA canceled the Gateway project earlier this year.
NASA is also collaborating with the U.S. Department of Energy to design and assemble the nuclear reactor that will power the mission.
Speaking at a meeting with the National Academy of Sciences' Aeronautics and Space Engineering Board in June, Lori Garver, Acting Associate Administrator for NASA's Exploration Systems Development, said: "We are reusing as much existing equipment as possible to minimize new development work. I fully recognize the significant execution challenges; the plan looks good on paper, but this is indeed our core approach."
It remains unclear how NASA will adjust its already allocated FY 2026 budget to support the Mars project or how the initiative will be incorporated into the FY 2027 appropriations review process. However, agency officials have indicated that sufficient funds can be reallocated at this stage to support the project's implementation.
Garver added: "We are reallocating all resources within the overall budget framework to ensure coverage for the tasks outlined in the 'Ignition Plan.' The current funding reallocation plan is generally feasible."
Regarding the Celestial Fall payload, NASA issued a separate statement noting that partial funding for the three reconnaissance helicopters will come from the Science Mission Directorate's "Future Mars Exploration Missions" budget, but declined to disclose the total cost of the Celestial Fall project.
The space agency stated: "As the overall mission design progresses into the formal detailed design phase, the final budget for the entire project is still being precisely calculated. By leveraging Space Reactor One to integrate launch and Mars delivery capabilities, this mission aligns with the Administrator's goal of cost reduction, focusing resources on projects that can yield scientific and exploration results in the near term."
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