Hypersonic start-up Hermeus has completed ground testing of its Quarterhorse Mk 1 vehicle and is preparing to launch a flight test campaign for the subsonic jet.
The Atlanta-based firm on 17 December said it had completed the ground portion of the Quarterhorse Mk 1 test campaign, which took place at Edwards AFB in California over a three-week period.
A video posted to the Hermeus LinkedIn page in November showed the covered Mk 1 jet being driven onto Edwards under cover of darkness on the back of a flatbed lorry.
Ground testing on the vehicle culminated with a 130kt (240km/h) taxi test under full afterburner, using a dry lakebed within the High Desert air base that is home to the US Air Force’s test pilot school. Hermeus says the Edwards Quarterhorse Mk 1 ground tests were used to validate aerodynamic model assumptions, assess the aircraft’s directional control and evaluate the performance of control surfaces.
“[The Mk 1’s] high-speed aerodynamic design introduces unique challenges, including a low aspect ratio wing, high wing loading and a low thrust-to-weight ratio,” the company says.
The unmanned aircraft’s remote flightdeck was also evaluated during the high-speed taxi tests, assessing for electromagnetic interference and the ability to optimise human control stations.
Hermeus had already completed a separate set of ground trials at its facility earlier this year. It now moves into the flight portion of the test campaign, which it says will be centred around take-off and landing, with periods of sustained flight intermixed.
“Key areas of focus for Hermeus include evaluating the effectiveness of control surfaces in flight, assessing performance and handling at high angles of attack, testing manoeuvrability under high wing loading and validating control gains and filters within the flight software,” the company says of the Mk 1 test campaign, which will also take place at Edwards AFB.
Hermeus received funding from the air force to support the maturation of hypersonic technologies and development of a flight vehicle. To achieve that, the company has adopted a rapid iteration strategy of designing and building successively more capable aircraft.
“With Quarterhorse Mk 1, we’ve proven our ability to design and build a clean-sheet aircraft in just 204 days,” says AJ Piplica, chief executive of Hermeus. “Through this test campaign, we are demonstrating how rapidly and rigorously our team can validate the aircraft for flight.”
Company president Skyler Shuford says the company’s goal remains developing one new aircraft per year, with the current focus being the Quarterhorse line.
The remotely piloted Mk 1 is the first flight-capable vehicle in the Quarterhorse family and the second overall, preceded by the ground-based Quarterhorse Mk 0 test article.
Hermeus plans to use the subsonic Mk 1 as a stepping stone toward its ultimate goal of breaking the Mach 5 hypersonic barrier with the forthcoming Quarterhorse Mk 3. A supersonic-capable Quarterhorse Mk 2 design will serve as a bridge between the two aircraft.
The start-up has set the goal of making the Mk 3 the world’s fastest aircraft, by breaking the airspeed record established by Lockheed’s SR-71 Blackbird nearly 50 years ago. In 1976, one of the twin-engined Blackbirds reached a velocity of 1,905kt (3,529km/h) – or M3.3, according to the USA’s Smithsonian National Air and Space Museum.
Design work is already underway on the supersonic Quarterhorse Mk 2 type, which will be powered by a Pratt & Whitney F100 turbofan, feature a delta wing with variable air intakes and be roughly the same size as a Lockheed Martin F-16 fighter.
The company is also experimenting with a proprietary pre-cooler system that will be featured on the supersonic Mk 2 and hypersonic Mk 3 Quarterhorse vehicles. While Hermeus has not revealed specific details, the technology will be critical to achieving hypersonic flight.
