G Norris, Going nuclear, Aviation Week & Space Technology, 14 August-3 September 2023, p 16

In US, DARPA and NASA are collaborating in a nuclear-powered rocket based on a fission reactor to heat the liquid hydrogen reactant, using a high-energy low-enriched uranium (HALEU) incorporating up to 20% of U-235. The project is named DRACO (Demonstration Rocket for Agile Cislunar Operations)