Engineers at NASA’s Marshall Space Flight Center (MSFC) in Alabama have completed the first cold-flow tests of a full-scale nuclear reactor prototype since the 1960s in support of space nuclear propulsion. The unit, similar to a 100-gallon drum, mimics nuclear thermal propulsion operations where hydrogen propellant heats via fission for exhaust at twice the efficiency of chemical rockets.
The tests, conducted from July to September 2025 on a small (44×72-inch) engineering development unit built by BWX Technologies (BWXT), simulated propellant flow without nuclear reactions, demonstrating that the design resists destructive vibrations and pressure waves. More than 100 tests provided the most detailed flow data in more than five decades, validating models for future flight systems.
“We’re doing more than proving a new technology,” said Jason Turpin, Manager of the Space Nuclear Propulsion Office at MFSC. “This test series generated some of the most detailed flow responses for a flight-like space reactor design in more than 50 years and is a key steppingstone toward developing a flight-capable system.”
Earlier in 2025, General Atomics Electromagnetic Systems (GA-EMS) completed several significant high-impact tests at MSFC to advance the development of Nuclear Thermal Propulsion (NTP) reactor technology. This is intended for rapid, agile cislunar transportation and deep space missions, including human missions to Mars. Tests were conducted in collaboration with NASA to verify the ability of the GA-EMS design-specific nuclear fuel to meet the high-performance specifications required to withstand the extreme operational conditions expected in space. GA-EMS conducted testing for NASA under a contract managed by Battelle Energy Alliance (BEA) Idaho National Lab (INL).
The nuclear fuel was tested with hot hydrogen flow through the samples and subjected to six thermal cycles that rapidly ramped-up to a peak temperature of 2600 K (Kelvin) or 4220° Fahrenheit. Each cycle included a 20-minute hold at peak performance to demonstrate the effectiveness of shielding the fuel material from erosion and degradation by the hot hydrogen. Additional tests were performed with varying protective features to provide further data on how different material enhancements improve performance under reactor-like conditions.
Dr Christina Back, Vice President of GA-EMS Nuclear Technologies & Materials noted: “To the best of our knowledge, we are the first company to use the compact fuel element environmental test (CFEET) facility at NASA MSFC to successfully test and demonstrate the survivability of fuel after thermal cycling in hydrogen representative temperatures and ramp rates.”
She added: “We’ve also conducted tests in a non-hydrogen environment at our GA-EMS laboratory, which confirmed the fuel performed exceptionally well at temperatures up to 3000 K, which would enable the NTP system to be two-to-three times more efficient than conventional chemical rocket engines. We are excited to continue our collaboration with NASA as we mature and test the fuel to meet the performance requirements for future cislunar and Mars mission architectures.”
NASA’s Space Nuclear Propulsion Office, under the Technology Demonstration Missions Program, is spearheading development alongside partners such as BWXT.
The earlier Demonstration Rocket for Agile Cislunar Operations (DRACO) programme, a joint initiative between the Defense Advanced Research Projects Agency (DARPA) and NASA to develop and test a nuclear thermal propulsion (NTP) system in orbit, was effectively cancelled in mid-2025.
The programme, which targeted a 2027 in-orbit demonstration of a nuclear-powered rocket, was terminated as part of the FY2026 President’s Budget Request, which proposed massive cuts to NASA’s technology development. The cuts eliminated funding for both Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP) projects.
DARPA and NASA cited changing requirements, with DARPA concluding that rapidly decreasing costs of conventional chemical space launches (driven by SpaceX) made the high research and development costs of nuclear thermal propulsion less economically attractive. Lockheed Martin, which was selected to design the vehicle in 2023, expressed disappointment.
The cancellation has been characterised as a major setback for the introduction of nuclear-powered spaceflight, reverting efforts back to traditional chemical technologies for the near term. While the federal programme has officially “completed” and transitioned its knowledge to NASA and other DOD branches, the technology remains of interest to private firms. However, without government backing, the 2027 test flight is on indefinite hold. Despite setbacks, NASA persists. Contract extensions in 2025 went to General Atomics and Standard Nuclear (acquirer of Ultra Safe Nuclear Technologies).
