China is developing a revolutionary air-breathing engine for next-generation fighter jets and hypersonic missiles.Designed to operate continuously from a stationary start-up to over Mach 6, the “contra-rotary ramjet engine” could replace the combined turbine-ramjet systems currently used in high-speed flight.After more than three decades of work, the engine prototype has been completed and experimentally verified, marking a potential step towards engineering applications.The next steps...