US hypersonic aircraft developer Hermeus has received experimental type certification for its latest Quarterhorse Mk 2.1 design.
Inspectors from the US Federal Aviation Administration granted a Special Airworthiness Certificate – Experimental Category (SAC-EC) to the supersonic-capable jet, which is undergoing flight testing at Spaceport America in New Mexico.
Hermeus announced the certification milestone on 12 March, 10 days after the unmanned Mk 2.1 logged its first sortie – a subsonic flight that included take-off and landing under internal power. Flights are being conducted in the airspace of the nearby White Sands Missile Range, a US Army test site.
The company says the granting of the SAC-EC gives Hermeus civil regulatory approval for its Quarterhorse flight test campaign as the company works toward achieving supersonic flight with the Mk 2.1.
“Their team conducted a rigorous inspection and gained real confidence in the aircraft. says Jay Wagemann, director of mission operations for Hermeus, says of the FAA. “Now, we will continue our flight test campaign, collecting vital data and pushing the limits of high-speed flight”.
Hermeus is attempting to build a reusable aircraft capable of achieving airspeeds of at least Mach 5 (3,307kt) – the generally accepted threshold for hypersonic flight.
The forthcoming Quarterhorse Mk 3 will attempt to break that hypersonic barrier, while the Mk 2.1 will power the programme beyond the M1 mark for supersonic flight.
An earlier Mk 1 vehicle demonstrated subsonic flight and demonstrated key elements at the core of the Quarterhorse design, including high-speed take-off and landing, aerodynamics profile and in-flight stability and control.
Critical aircraft subsystems, including propulsion, fuel delivery, hydraulics, power and thermal management, and the flight software, were also evaluated during Mk 1 testing and fed into the Mk 2 design.
Hermeus says the Mk 2.1 campaign will ramp through progressively higher altitudes and airspeeds as the company builds toward a supersonic flight. The jet is powered by a single Pratt & Whitney F100 turbofan fighter engine.
At the same time it is developing flight vehicles, Hermeus is also advancing a proprietary engine design called Chimera that will eventually power the Quarterhorse Mk 3 to high-Mach and hypersonic flight.
That turbine-based combined cycle (TBCC) powerplant will incorporate a proprietary pre-cooling system and integrate a standard turbofan with a separate ramjet engine into a single propulsion system able to transition from subsonic through to hypersonic speeds.
Hermeus says it current development timeline will see the delivery of an operational, reusable hypersonic capability before 2030.
