Quarterhorse
Overview
An iterative program of unmanned, remotely piloted test aircraft designed to unlock high-speed flight one step at a time. Hermeus says the Quarterhorse program spans four aircraft, each purpose-built to validate a specific technical challenge and feed the next build.
Mk 1 flew at Edwards AFB in May 2025. Mk 2.1, roughly F-16-sized and powered by a Pratt & Whitney F100, flew in February 2026 and on its third flight from Spaceport America hit Mach 1.21 on May 26, 2026, becoming the first privately-developed unmanned supersonic jet and clearing FAA approval for up to seven supersonic flights through year-end. On a fourth flight in mid-July 2026, Mk 2.1 extended its top speed to Mach 1.6, beyond its previously announced Mach 1.25-1.50 design range. In its fifth flight since spring 2026, Mk 2.1 completed an unmanned stores-separation test in late July 2026 under DIU's HyCAT program, safely releasing an external payload in flight. The next airframe, Mk 2.2, has arrived at Spaceport America from Atlanta and is targeted to reach Mach 2-plus while demonstrating a Hermeus-developed pre-cooler and variable-geometry inlet, with Mk 2.3 - built with a steel airframe at the new El Segundo facility - now targeted for the first half of 2027 aiming for Mach 3, and a Chimera-powered hypersonic Mk 3 before 2030.