Atlanta-based aerospace firm Hermeus has announced a significant achievement: its experimental uncrewed aircraft, the Quarterhorse Mk 2.1, has successfully broken the sound barrier. The trials took place in New Mexico, within a restricted airspace above White Sands Missile Range at Spaceport America. During its third flight mission, the aircraft reached a speed of Mach 1.21, approximately 1480 km/h.
Hermeus management has described this event as a historic milestone, marking the first supersonic flight of an uncrewed aircraft of this nature, developed entirely through private investment. The Mk 2.1 modification achieved supersonic capabilities in less than three months after its initial flight in early March, and a mere 364 days after the prototype Mk 1 first took to the skies.
Hermeus’s engineering philosophy is rooted in rapid prototyping, where teams prioritize frequent hardware updates over extended production cycles. Data gathered from each Quarterhorse Mk 2.1 flight is immediately applied to refine the aircraft’s aerodynamics, control systems, and propulsion. The current aircraft serves as a testbed for upcoming versions, with the Mk 2.2 modification, featuring the Chimera II combined engine, already under development, followed by plans for the Mk 2.3.
The Quarterhorse initiative encompasses a series of prototype demonstrators (ranging from Mk 0 to Mk 3) designed to validate high-speed flight technologies. These advancements will form the foundation for two future projects: the military-focused Darkhorse and the commercial Halcyon. Darkhorse is intended for defense and reconnaissance missions at speeds exceeding Mach 5. Meanwhile, Halcyon aims to be a supersonic passenger jet capable of traveling between New York and London in just 90 minutes.
Hermeus has surpassed the speed of Boom Supersonic’s XB-1 uncrewed demonstrator (Mach 1.122 — 1375 km/h), which is being developed for the Overture commercial airliner. Concurrently, NASA and Lockheed Martin are concluding flight tests for their quiet supersonic aircraft, the X-59, in preparation for its initial high-speed trials.
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