Scientists take first look inside one of world’s most extreme engines

Scientists at the US Naval Research Laboratory (NRL) have made a breakthrough in understanding solid-fuel ramjet (SFRJ) engines by using advanced optical diagnostic techniques to observe the internal combustion processes for the first time. SFRJs are air-breathing engines that use atmospheric oxygen instead of carrying an oxidizer, which can increase missile range by 200-300% within the same size. However, studying these engines has been challenging due to extreme heat, soot, and high-speed flows inside the combustor. The NRL team overcame these obstacles by precisely measuring flame temperatures, fuel regression rates, vapor transport, and decomposition products, providing new data that was previously unattainable with traditional probes. The researchers combined these experimental insights with high-fidelity computational simulations, such as Detached Eddy Simulation (DES) and Large Eddy Simulation (LES), to better capture the complex flow dynamics and chemical reactions inside the engine. This approach contrasts with earlier trial-and-error methods that lacked detailed understanding of the internal