Hermeus breaks the sound barrier with its unmanned Quarterhorse and brings new pace to hypersonic development

Hermeus’s Quarterhorse Mk 2.1 reached Mach 1.21 on its third test flight. That is not hypersonic speed yet, but it matters because the US company took a remotely piloted jet aircraft past the sound barrier less than three months after its first flight, while already building the next, faster prototypes.