Bolstered by a $60 million Air Force-backed contract, Hermeus is working toward developing the full-scale flight engine for its Quarterhorse concept aircraft as the aerospace start-up barrels toward a potential first flight test of the platform within the first half of 2023. Known for its goal to develop a Mach 5 passenger jet, the Georgia-based company in late July won a deal to boost hypersonic development from the service and a group of venture capital firms. Some four months later,...