Author: Wu Haowei, Huang Ruixin, Han Shuaiqi
The topic of hypersonic has become hot in the United States, and the company Hermeus, founded at the end of the last decade, is working on the Quarterhourse family of aircraft. Continuously accumulate experience and improve technology to develop full-fledged hypersonic aircraft.
Hermes was founded in 2018 by former employees and young professionals of several major aircraft manufacturers. Its main task is the development of a multipurpose air platform with hypersonic flight speeds suitable for use in the military and civilian spheres. In its early stages, the company proposed several concepts for such equipment.
The direction of the aircraft began with the study of brackets and wind tunnels. Then it was planned to sequentially develop several experimental unmanned aerial vehicles for ground and flight tests. These projects are collectively known as the Quarterhorse, which reflects the need to achieve maximum flight speed without high range requirements.
The second area of work was the development of engines for flying Quarterhorses. According to the results of the study, it was decided to use a combined cycle system combining a turbojet engine and a ramjet engine. This architecture is named after the name of the project - Chimera ("Chimera").
In the new project, it is planned to use all modern design and technological processes that can speed up development and prototyping. The design and calculation of structures are carried out in electronic form, and additive technology is used to manufacture prototypes, mainly metal 3D printing, etc.
Hermes' technology demonstrator, the Quarterhorse, ultimately aims to reach speeds in excess of Mach 4 and perhaps even more due to the company's unique propulsion system design. But before this high-speed platform can fly, it must learn to glide. That's exactly what the company's recently launched Quarterhorse Mk0 prototype was aiming for.
Once completed, the non-flying aircraft will provide Hermes with the opportunity to begin testing on-board systems such as remote flight controls, while production of the company's first flying prototype, the Quarterhorse Mk1, is underway.
The Quarterhorse is about 40 feet long and is powered by a turbo combined cycle (TBCC) engine of Hermes' own design, which is known as the Chimera. As the name suggests, this air-breathing jet engine can actually be thought of as two engines in one: the first is a turbojet and the second is a ramjet. Turbojet engines excel at providing power to aircraft from a complete stop to around Mach 3. The ramjet engine takes over at high speeds; Chimera's ramjet engine is designed to accelerate the Quarterhorse to more than Mach 4, and possibly even Mach 95,000 at altitudes of up to 5 feet.
This will allow the intrepid startup not only to have the world's fastest reusable jet, but also to make Hermes the first company in the world to deploy a reusable hypersonic aircraft.
With Quarterhorse, Hermes intends to move to its military-specific platform, Darkhorse, which will be powered by a larger, more powerful TBCC engine and based on the Pratt & Whitney F100 turbofan engine. Powering high-performance fighters such as the F-15Eagle, the F100 will have more than four times the thrust of Chimera's current J85, allowing for larger payloads and faster speeds.
In parallel with the work on the aircraft, the company was also developing the Chimera engine. The first version of it was built on the basis of the General Electric J85 turbojet engine. Compared to the previous version, the new version complements the straight-through profile of its own design. In the fall of 2022, Hermes tested this engine and confirmed the possibility of operating in two modes. Currently, it is developing a larger, more powerful Chimera II engine, which is based on the Pratt & Whitney F100 engine. The engine is designed for the future Mk 2 supersonic UAV and subsequent hypersonic aircraft. The development and testing of such a product should be completed before the completion of the construction of the unmanned flying laboratory, that is, during 2025.
In recent years, hypersonic missiles have attracted a lot of attention due to their combination of speed and maneuverability, which allow them to disrupt the most advanced air defense systems, but the incredible cost of these weapons has led many to question whether they can provide a real air defense system. Combat value. According to a recent Pentagon estimate, each hypersonic missile could cost up to $106 million, about $27 million more expensive than the brand-new F-35A. According to reports, Hermes is not the only company involved in this project, there is at least one publicly disclosed plan to deploy hypersonic drones (some kind) within the secret range of the US Air Force research laboratory. The Air Force intends to use a faster scramjet engine, and not to combine a turbofan engine with a ramjet engine, as Hermes did.
From a practical point of view, combined-cycle turbofan/ramjet and turbofan/scramjet work very similarly, but a ramjet slows down the incoming air to a more controllable subsonic speed before mixing with fuel and igniting propulsion, while a scramjet allows air to enter and flow through them at supersonic speeds. As a result, a ramjet engine may not be able to go above Mach 6, while a scramjet may continue to accelerate to Mach 10 or beyond.
However, all of these increases in speed come with a massive increase in complexity and cost. Scientists liken ignition in the supersonic gas stream of a scramjet engine to lighting a match in a hurricane. Although there have been many successful demonstrations of scramjet technology over the years, the successful application of scramjet to combat aircraft or weapons presents a range of engineering challenges.
However, ramjet engines are based on older and more mature technology, so there are fewer technical hurdles to overcome, which could make Hermes the first company to exceed Mach 5. But before doing all that, the Quarterhorse Mk0 needs to prove that it is capable of rigorous testing on the ground.