Hermeus’ Quarterhorse Mk 2.1 achieves first uncrewed supersonic flight at Mach 1.21
US hypersonics startup Hermeus has broken the sound barrier with its uncrewed Quarterhorse Mk 2.1, less than a year after first flight. The aircraft reached a top speed of Mach 1.21, marking the start of an experimental supersonic test campaign for the large unmanned jet.