The US Department of Defense’s (DOD’s) Defense Advanced Research Projects Agency (DARPA) has cancelled the Demonstration Rocket for Agile Cislunar Operations (DRACO) project to develop a nuclear thermal engine for spacecraft for economic reasons.
DRACO, launched in 2020 with $10m, aimed to develop and place a nuclear thermal propulsion (NTP) system above low Earth orbit in 2025. It intended to develop and demonstrate a high-assay low-enriched uranium (HALEU) NTP system. In 2021, DARPA awarded contracts to General Atomics, Blue Origin, and Lockheed Martin for the first phase of DRACO. NASA was working on similar NTP rockets and, in 2023, DARPA and NASA agreed to collaborate on the project. NASA was responsible for the nuclear rocket engine, and DARPA for the space vehicle and for securing regulatory approval to launch a nuclear reactor into orbit.
“When DRACO was originally conceived of, that was pre- the precipitous decrease in launch costs that has been driven largely by SpaceX capabilities and the continued decrease that Starship offers if we can get it operational,” DARPA Deputy Director Rob McHenry told the Washington-based Mitchell Institute for Aerospace Studies.
“And it was also based on analysis at the time that showed that nuclear thermal was likely to be the optimal solution for a set of national security related admissions, as well as solar system exploration,” he added. “And over the execution of that programme, both of those assumptions started to get weaker and weaker. As the launch costs came down, the efficiency gain from nuclear thermal propulsion relative to the massive R&D costs necessary to achieve that technology started to look like less and less of a positive ROI [return on investment].”
The cancellation of DRACO was first reported in early June by Ars Technica in an analysis of NASA’s fiscal 2026 budget request that included no funding for the project. “This budget provides no funding for Nuclear Thermal Propulsion and Nuclear Electric Propulsion projects,” according to a technical supplement to the NASA budget proposal. “These efforts are costly investments, would take many years to develop, and have not been identified as the propulsion mode for deep space missions. The nuclear propulsion projects are terminated to achieve cost savings and because there are other nearer-term propulsion alternatives for Mars transit.”
It seems DARPA had already decided to pull out of the project. Ars Technica quoted NASA as saying that the budget proposal “reflects the decision by our partner to cancel” the DRACO mission. A DARPA spokesperson subsequently confirmed the agency was closing out the project. “DARPA has completed the agency’s involvement in the Demonstration Rocket for Agile Cislunar Orbit (DRACO) programme and is transitioning its knowledge to our DRACO mission partner, the National Aeronautics & Space Administration (NASA), and to other potential DOD programmes,” the spokesperson said in a response to written questions.
There is no announcement on DARPA’s website. The page on DRACO simply says: “This program is now complete. This content is available for reference purposes. This page is no longer maintained.”
