US hypersonic aircraft developer Hermeus has begun taxiing tests for its first aircraft, according to recently released footage.
The Atlanta-based manufacturer posted a video on several social media platforms showing the chrome-colored Quarterhorse Mk 1 moving up and down a runway during what Hermeus describes as medium- and high-speed taxi runs.
“We are getting a lot of iterations of rolling tests with Quarterhorse Mk 1,” Hermeus said Aug. 22. “These repeated runs allow us to collect data on all integrated systems.”
The company had teased the first flight of the Mk 1 earlier this year and announced in March that the single-engine jet would “take to the skies” at Edwards AFB in the coming summer months.
However, that schedule now appears to have been delayed, as footage from taxi tests shows lush greenery not found at the desert base in California where the U.S. Air Force (USAF) flight test program is conducted.
Hermeus did not immediately respond to a request for comment on the Quarterhorse testing plan.
In November 2023, the Pentagon’s Defense Innovation Unit provided Hermeus with research and development funding to support the advancement of hypersonic technologies and the development of an aircraft.
The unmanned Mk 1 is the first flight-capable vehicle in the Quarterhorse series and the second overall, after the ground-based Quarter Horse Mk 0 Test article. Early ground tests of the Mk 0 took place at the USAF’s Arnold Engineering Development Complex in Tullahoma, Tennessee.
Hermeus plans to use the subsonic Mk 1 as a stepping stone to its ultimate goal of breaking the Mach 5 supersonic barrier with the upcoming Quarterhorse Mk 3. Quarter Horse Mk 2 The design will serve as a bridge between these two aircraft.
The start-up aims to make the Mk 3 the fastest aircraft in the world, breaking the current speed record set almost 50 years ago by Lockheed’s SR-71 Blackbird.
In 1976, one of the twin-engine Blackbirds reached a speed of 1,905 knots (3,529 km/h) – or M3.3, according to the Smithsonian National Air and Space Museum of the United States.
To achieve this, Hermeus focuses heavily on the rapid development of new aircraft designs.
“One aircraft per year,” the company announced its goal in April.
Quarterhorse Mk 0 was designed and built in less than six months, while the process for the Mk 1 vehicle took just seven months, according to Hermeus.
Design work has already begun on the supersonic Mk 2 model, which will be powered by a Pratt & Whitney F100 turbofan, feature delta wings with variable air intakes and will be approximately the size of a Lockheed Martin F-16 fighter jet.
The company is also experimenting with a proprietary Pre-cooler system which will be used in the Mk 2 and K3 Quarterhorse aircraft. Although Hermeus has not disclosed specific details, the technology will be crucial to the realization of supersonic flight.
Pre-cooling is the cooling of intake air before compression and combustion. Colder intake air allows conventional turbojet engines to operate at higher speeds, with greater efficiency and less power degradation.
Although Hermeus has not disclosed design details, pre-cooling can be achieved through the use of a heat exchanger and a cryogenic fuel, such as liquid hydrogen.
Such a system is an integral part of the Hermeus approach to breaking the Mach 5 hypersonic barrier. It uses a standard engine to accelerate to a low Mach speed flight before switching to a separate ramjet engine to reach hypersonic speed.
