Russia’s new class of jet-powered drones rip across the night sky in Kyiv at hundreds of kilometres per hour, leaving Ukrainian air-defence units only moments to intercept them. It’s rarely enough time. With many of the drones getting through to the capital, defence manufacturers are scrambling to develop a new generation of interceptors to counter the deadly threat. They are building their own jet propulsion systems and training artificial intelligence to help guide the chase. They need to move...