Hermeus hypersonic aircraft completes maiden flight at subsonic speeds
The hypersonic aircraft Hermeus Quarterhorse Mk 2.1 has completed its maiden flight. A first important step to test high-speed flights later.
The Hermeus Quarterhorse Mk 2.1 takes off.
(Image: Hermeus)
The US aerospace start-up Hermeus has tested the prototype of its unmanned hypersonic aircraft Quarterhorse Mk 2.1 for the first time in a maiden flight – initially only at subsonic speeds. Hermeus announced this on Tuesday. In contrast to the previous prototype Mk 1, which had already completed its maiden flight in early June 2025, the new version is significantly larger and heavier.
Hermeus has designed the Mk 2.1 prototype to be almost three times larger and about four times heavier than the Mk 1. This puts the unmanned hypersonic aircraft in the size class of a Lockheed Martin F-16. Quarterhorse is equipped with an F100-PW-229 engine from manufacturer Pratt & Whitney, which has been specially modified for the aircraft. A similar engine is also used in an F-16 Fighting Falcon.
The Quarterhorse Mk 2.1 took off on March 2, 2026, from Spaceport America in the US state of New Mexico for its maiden flight. The aircraft was remotely controlled by a ground crew. The flight was conducted entirely at subsonic speeds.
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The engineers initially evaluated the critical systems of the unmanned hypersonic aircraft. These include, for example, the propulsion components, flight control, and aerodynamics. In addition, tests were conducted on structural load and airflow control to ensure a safe transition from subsonic to transonic to supersonic flight later on. Only when these tests have yielded positive results will the aircraft's performance be gradually increased to determine its flight characteristics at higher speeds.
Iterations to Hypersonic Flight
Hermeus proceeds with the development of its hypersonic aircraft by developing multiple prototypes to test specific characteristics on each, rather than painstakingly developing a single prototype until the final aircraft version. Early versions are used for ground tests, for example, to validate ground roll behavior, while later prototypes are intended to validate flight capability up to supersonic speeds. This approach allows for faster development of aircraft for hypersonic flight.
The Quarterhorse Mk 2.1 is already designed to test all basic systems at higher speed ranges. Gradual extensions are intended to transition it to the next version, Mk 2.2. Presumably, the variable inlet system for maintaining a stable airflow at increasing speeds will then also be used in the delta-wing aircraft with variable wings. Only with this version will a supersonic flight attempt be made.
The plan is to later replace the engine with a Chimera drive, which combines a ramjet with a conventional turbofan. With this TBCC technology (Turbine Based Combined Cycle), speeds of up to approximately Mach 4 will then be achievable. However, this step is planned only for the subsequent version, Quarterhorse Mk 3.
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However, Hermeus is already thinking one step further: with Darkhorse, the aerospace start-up is already working on the development of a reusable hypersonic platform for aviation that can be used for military missions.
(olb)
