Hermeus unveils Ramjet-X for high-Mach
Hermeus has revealed its Ramjet-X expendable test vehicle, designed to be air-launched from its Quarterhorse aircraft at Mach 3 to provide cheaper
Hermeus has unveiled its Ramjet-X vehicle, an expendable ramjet-powered craft designed to be air-launched from its Quarterhorse uncrewed aircraft. The system aims to drastically reduce the cost of testing components at speeds above Mach 3.
According to the company, Ramjet-X is central to a new commercial service it calls "high-Mach Flight Test as a Service." Customers could integrate payloads, sensors, communications systems, autonomy software, material samples, and propulsion technologies onto the vehicle for testing in sustained high-speed conditions. "High-speed flight testing is extremely expensive, and you don't get many shots at it," Hermeus chief executive Zach Shore said in the announcement.
Technical specifications and flight profile
In an interview with Axios, Shore provided specific dimensions and performance goals for the Ramjet-X system. The vehicle itself is roughly 6.7 meters (22 feet) long and 2.1 meters (7 feet) across. A single Quarterhorse aircraft is expected to eventually carry two of these vehicles.
The planned test sequence involves the Quarterhorse carrier aircraft accelerating to approximately Mach 3 before releasing Ramjet-X. Following separation, the ramjet vehicle would then climb to an altitude of about 100,000 feet (approximately 30,500 meters) and cruise near Mach 4 for tens of minutes. Hermeus is targeting a first flight of the integrated system within a year.
| Parameter | Specification |
|---|---|
| Vehicle Length | 6.7 meters (22 feet) |
| Vehicle Width | 2.1 meters (7 feet) |
| Launch Speed (from Quarterhorse) | Mach 3 |
| Target Cruise Altitude | 100,000 feet (~30,500 meters) |
| Target Cruise Speed | Near Mach 4 |
| Cruise Duration | Tens of minutes |
| Quarterhorse Payload Capacity | 2 vehicles (eventual goal) |
Development timeline and infrastructure
Integrated vehicle testing of the full Ramjet-X and Quarterhorse system is planned for 2027. The company is currently conducting ramjet engine testing at its HEAT facility in Jacksonville, Florida. Simultaneously, it is developing the necessary high-temperature structures at its corporate headquarters in El Segundo, California.
The company's development platform, Quarterhorse, has already demonstrated supersonic capability. The Quarterhorse Mk 2.1 aircraft reached Mach 1.21 on its third flight in May 2026. That flight occurred after the Federal Aviation Administration (FAA) issued a Special Airworthiness Certificate in the Experimental Category for the aircraft.
Historical precedent and company progress
The concept of a larger aircraft carrying a high-speed ramjet vehicle has historical precedent. Hermeus notes it recalls the 1960s-era Lockheed M-21 and D-21 pairing, where a modified A-12 aircraft carried a ramjet-powered reconnaissance drone.
Hermeus moved its corporate headquarters from Atlanta, Georgia, to El Segundo following the closure of a $350 million Series C funding round in April 2026. The company states that using the reusable Quarterhorse as a launch platform, instead of an expendable rocket booster, is key to making repeated high-Mach testing more affordable for its future customers.
