The National Aeronautics and Space Administration (NASA) and the Defence Advanced Research Projects Agency (DARPA) have announced a new partnership to develop advanced rocket technologies that use nuclear power for propulsion. Despite significant advances in aerospace engineering over the decades, the amount of thrust a rocket can generate is still limited by conventional fuels such as kerosene and hydrogen. This constrains the speed that a vehicle can reach, making longer distance missions challenging and strenuous, particularly for the crew involved.
NASA Will Be Responsible For Developing Nuclear Rocket Engine With DARPA Focusing On Vehicle Operations
NASA announced the engine development as part of the American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum in Maryland today. At a fireside chat at the event, DARPA’s director Ms. Stefanie Tompkins explained that recent advances in nuclear technology had enabled her agency to take more ‘risks’ with it. She outlined that the shift to High-Assay Low-Enriched Uranium (HALEU) has a higher proportion of enriched Uranium in the fuel mixture when compared to the fuel that is currently used in light-water nuclear reactors. This allows it to generate more power; however, currently, the concentration is still lower than what is required for nuclear submarines, aircraft carriers and weapons.
NASA has signed an Interagency Agreement (IAA) with DARPA, which delegates responsibility for demonstrating nuclear propulsion in space to both parties. As part of the agreement, NASA will be responsible for designing what it dubs a nuclear thermal rocket (NTR) technology and the NRT engine. This includes building and developing the nuclear reactor, all aspects of the engine, testing the engine on the ground, helping DARPA procure HALEU, and vehicle integration.
The engine developed by NASA will have to be integrated into a vehicle, which is where DARPA comes in. This vehicle is called an experimental NTR vehicle (X-NTRV), and DARPA will integrate the launch vehicle into the X-NTRV (implying that a traditional rocket will launch the NTR-equipped vehicle), operating and disposing the X-NTRV and perform all associated activities. Additionally, all systems developed under NASA’s part of the agreement will be unclassified.
A central issue for nuclear propulsion is safety, which also creates regulatory hurdles for the technology. At this front, NASA’s deputy administration Pam Melroy explained that
Ms. Tompkins added that when it comes to safety, the system will be designed in a manner that the engine will not be operating until it reaches space and that it will use an orbit that will not ‘degrade’ until the engine itself is safe to enter Earth again. The engine itself will not emit any radioactive exhaust, with only gaseous hydrogen coming out of a potential nozzle. A couple of minutes later, Ms. Melroy also shared more details about the engine, explaining that:
Currently, the NASA-DARPA agreement calls for a launch readiness review, one of the final reviews before launch in the fiscal year 2027 (roughly four years from now). The X-NTRV will be flown at a high orbit, and according to the NASA official:
