Hermeus has unveiled Ramjet-X, an expendable ramjet-powered vehicle designed to be released in flight from beneath its Quarterhorse uncrewed aircraft. According to AeroTime, the company said the vehicle is intended to reduce the cost of high-Mach airbreathing flight testing.
Ramjets produce no thrust from a standing start and conventionally depend on an expendable rocket booster to reach operating speed. Hermeus said Quarterhorse would instead carry Ramjet-X to the required speed and altitude, release it, and return for further test sorties.
The company is also positioning the vehicle as a commercial offering it calls “high-Mach Flight Test as a Service”. According to the release, customers would be able to integrate payloads, sensors, communications and computing systems, autonomy software, material samples and propulsion technologies onto Ramjet-X for testing in sustained high-Mach conditions.
Chief executive Zach Shore said in the statement: “High-speed flight testing is extremely expensive, and you don’t get many shots at it.” Ramjet engine testing is underway at the Hermeus HEAT facility in Jacksonville, Florida, and high-temperature structures are being developed at its El Segundo, California headquarters. Integrated vehicle testing is planned for 2027.
In an interview with Axios published on September 9, 2026, Shore said Ramjet-X measures roughly 6.7 meters (22 feet) long and 2.1 meters (7 feet) across. Separation would occur at about Mach 3, and the vehicle would then climb to about 100,000 feet (approximately 30,500 meters) and cruise near Mach 4 for tens of minutes. A first flight is expected within a year, and a single Quarterhorse should eventually carry two vehicles. The pairing recalls the Lockheed M-21 and D-21 of the 1960s. Quarterhorse Mk 2.1 reached Mach 1.21 on its third flight in May 2026, after the Federal Aviation Administration (FAA) issued a Special Airworthiness Certificate in the Experimental Category. Hermeus closed a $350 million Series C round in April 2026 and moved its corporate headquarters from Atlanta, Georgia, to El Segundo.
