Quarterhorse Mk 0 Begins Testing
October 12, 2023
In 1976, an SR-71 soared over Beale Air Force Base at a speed of 2,193.2 miles per hour breaking the all-time jet-powered airspeed record. The record has not been broken since.
Our goal of making hypersonic aircraft mainstream begins with Quarterhorse. Its mission is to demonstrate that our turbine-based combined cycle engine, Chimera, can transition from turbojet mode to ramjet mode in-flight. If successful, we’ll surpass the SR-71’s long-held record.
At less than 40 feet in length, this small aircraft will provide an extensive amount of development and testing learning which in turn will de-risk our future vehicles, Darkhorse and Halcyon. Once in production, Quarterhorse will be used for commercial testing and development purposes.
REDUCING THE STAKES, INCREASING THE LEARNINGS
Quarterhorse won't rush to surpass the SR-71's airspeed record. Instead, it will be part of a deliberate, step-by-step strategy. Just as our business roadmap includes three aircraft of increasing complexity (Quarterhorse → Darkhorse → Halcyon), we are currently developing four unique Quarterhorse vehicles, each designed for a specific mission.
Our rapid prototyping approach deliberately mitigates risk.
Rather than consolidating all uncertainties and variables into a single Mach 4 aircraft, we are spreading the risks across multiple vehicles, which will enable us to learn more quickly. This iterative, hardware-intensive method is our key to speeding up aircraft development.
quarterhorse MK 0
Mk 0 is a unique prototype resembling a typical iron bird, but is distinguished by incorporating an engine to demonstrate remote command and control during taxiing. Serving as a comprehensive testbed for Quarterhorse, Mk 0 will validate various systems including: electrical, hydraulic, pneumatic, avionics, steering, and propulsion. Although it won't take flight, this prototype vehicle will put to the test our Flight Deck's command and control system.
The Flight Deck has been designed from the ground up to support off-grid stand-alone operations in austere environments. It supports a pilot, payload operator, four operational analysts, and jump-seats for observers.
This vehicle harnessed our team’s experience in engineering and challenged the “way it’s always been done” – all in the pursuit of hypersonic speed. Balancing experience with analysis and rigorous testing is intrinsic to our culture.
As Mk 0 gears up for taxi testing, it signifies more than just vehicle construction but rather a different type of aerospace development and manufacturing that embraces integrated hardware and software testing with a culture of iteration and speed. Meanwhile, The Factory, which is “building the machine that builds the machine” is continuing to grow, allowing Hermeus to build and test faster.
WHAT’S NEXT
Our next vehicle, Quarterhorse Mk 1, is actively taking shape in The Factory. Designing, building, and testing multiple aircraft simultaneously is the new normal.
The team continues to grow exponentially, and we are strategically adding new offices and testing facilities across the country.
ABOUT HERMEUS
Hermeus is a high-speed aircraft manufacturer focused on the rapid design, build, and test of high-Mach and hypersonic aircraft for the national interest. Working directly with the Department of Defense, Hermeus delivers capabilities that will ensure that our nation, and our allies, maintain an asymmetric advantage over any and all potential adversaries.
Contact us at press@hermeus.com or follow us online.
Find additional photos on Unsplash.
Find 4K footage for download on Vimeo.

