American aerospace company Hermeus has unveiled Ramjet-X, a disposable high-speed aircraft powered by a ramjet engine, designed to be launched from its reusable Quarterhorse drone.
Under the planned flight profile, Quarterhorse will first carry Ramjet-X to altitude and accelerate it to roughly Mach 3. Ramjet-X will then separate and ignite its own ramjet engine, while Quarterhorse returns to base to be reused.
The company said this launch method is needed because ramjet engines cannot operate efficiently from a standing start and require an initial boost to reach operating speed. That boost is usually provided by a separate engine or a disposable booster rocket. Hermeus said replacing those with a reusable drone should cut costs and simplify high-speed flight testing.
Flight Test as a Service
Hermeus is developing Ramjet-X primarily as a testing platform, which it intends to offer to customers under a model it calls Flight Test as a Service. The aircraft is designed to carry a range of experimental payloads, including sensors, communications equipment, computing systems, autonomous systems, new materials and components for future engines.
The Ramjet-X engine is already undergoing ground-based static fire testing at the HEAT facility in Florida. Hermeus plans to begin full integrated flight tests of the aircraft in 2027. The company has not yet disclosed the vehicle's size, weight, top speed or flight duration.
Quarterhorse test progress
Hermeus is continuing parallel testing of the reusable Quarterhorse drone. In May, the Mk 2.1 version reached a speed of Mach 1.21, about 1,480 km/h. The next variant, Mk 2.3, is expected to become the first aircraft in the Quarterhorse family capable of reaching Mach 3, or 3,675 km/h, the speed needed to air-launch Ramjet-X.
Echoes of the Cold War
The concept recalls the American D-21 reconnaissance drone from the Cold War era, which was launched from a modified M-21 aircraft. Hermeus is applying a similar approach, but for regular commercial testing of advanced high-speed technologies rather than reconnaissance.
