Four times faster than the Concorde, capable of taking passengers from New York to London in less than an hour at Mach 5.5, and with an engine that switches from turbojet to ramjet mid-flight at Mach 3.5, the Hermeus Quarterhorse went from paper to its first flight in just 19 months.

Written by Valdemar Medeiros

Published on 29/05/2026 at 16:55

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Quarterhorse Mk 1 makes first flight, accelerates Hermeus hypersonic program and brings the Mach 5 Halcyon passenger plane project closer.

According to The Aviationist, the American startup Hermeus conducted the first flight of the unmanned prototype Quarterhorse Mk 1 at Edwards Air Force Base, California, on a date publicly announced on May 27, 2025. The prototype took only 19 months from design to inaugural flight, a timeframe the company describes as the fastest in jet aircraft development in the last 80 years.

The Quarterhorse Mk 1 is equipped with a General Electric J85 engine, the same used in the F-5 fighter and the T-38 trainer, and was created to demonstrate high-speed takeoff and landing on conventional runways. This point is considered by the company as the most critical capability for any future commercial hypersonic aircraft.

Hermeus wants to create hypersonic plane with startup pace and goal of one prototype per year

Hermeus was founded in Atlanta by former engineers from SpaceX, Generation Orbit, and Blue Origin, with the proposal to apply to hypersonic aviation the same model of accelerated iteration that SpaceX used in rocket development. The company has already raised over US$ 100 million by May 2025.

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Chimera Engine is the central technology of Quarterhorse and the greatest challenge of hypersonic flight

The technological center of the program is not just the aircraft, but the Chimera engine, a combined cycle turbine ramjet propulsion system that Hermeus is developing in parallel with the prototypes. According to the text, this is the most important element to overcome the main technical obstacle of horizontal takeoff hypersonic flight.

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The Chimera combines pre-cooler, turbojet, and ramjet. At lower speeds, the system uses conventional propulsion to accelerate the aircraft to somewhere between Mach 3 and Mach 3.5. From there, the ramjet kicks in, allowing continued acceleration to Mach 5 and beyond.

The transition between these two propulsion modes is the most difficult point of hypersonic engineering. Hermeus claims to have demonstrated this capability in a wind tunnel in November 2022, but the decisive step will be to show the change in real flight, which is planned for the next phases of the Quarterhorse program.

Quarterhorse sequence was designed to solve each stage of hypersonic flight

The Quarterhorse family was organized to tackle each technical obstacle separately. The Mk 0 was a non-flying prototype, built in six months, with test objectives completed in 37 days at the Arnold Engineering Development Complex in Tennessee.

Four times faster than the Concorde, capable of taking passengers from New York to London in less than an hour at Mach 5.5 — Quarterhorse Mk 1 First Flight – Disclosure

The Mk 1, now flown, validates the basic operations of takeoff and landing. The Mk 2, larger and equipped with a Pratt & Whitney F100 engine, the same as the F-16, is expected to demonstrate autonomous supersonic flight up to Mach 3. The Mk 3 will be the first to attempt the transition between turbojet and ramjet in real flight and aim to break the speed record of the SR-71 Blackbird, set at Mach 3.4 in 1976.

Next, the Mk 4 is expected to be the first in the line to reach full hypersonic speeds. This step-by-step architecture allows the company to validate one problem at a time, reducing technical risk and accelerating learning between prototypes.

Halcyon is the hypersonic passenger plane that Hermeus wants to put in the air before the end of the decade

The ultimate goal of the program is the Halcyon, a hypersonic passenger plane with 20 seats, a cruising speed of Mach 5, and the ability to use conventional runways. According to the text, the company’s goal is to have it flying before the end of the decade.

At a speed of about Mach 5.5, the proposal would allow connecting New York to London in less than an hour. The comparison used in the text is with the Concorde, retired in 2003, which made the same journey in about 3.5 hours at Mach 2.04.

In addition to the civil market, Hermeus is also developing the Darkhorse, an unmanned hypersonic aerial system aimed at defense and security, leveraging the same technological base created throughout the evolution of the Quarterhorse.

Investors and the American government bet that Hermeus can change hypersonic aviation

The composition of Hermeus‘ capital helps explain the weight of the project. Among the investors are Raytheon Technologies, Khosla Ventures, and Sam Altman, in addition to funding from the American government itself through the Air Force Research Laboratory.

The first flight of the Quarterhorse Mk 1 does not solve the problem of hypersonic transport on its own, but it represents a concrete validation of the company’s approach. What was once just a startup promise has turned into a real aircraft capable of taking off and advancing the program’s schedule.

With the Mk 2, the Chimera test, the attempt to surpass the SR-71 record, and the goal of reaching the Halcyon, Hermeus is trying to transform an idea that for decades was restricted to military programs and laboratories into a concrete path for the commercial hypersonic plane.

Four times faster than the Concorde, capable of taking passengers from New York to London in less than an hour at Mach 5.5, and with an engine that switches from turbojet to ramjet mid-flight at Mach 3.5, the Hermeus Quarterhorse went from paper to its first flight in just 19 months.

Quarterhorse Mk 1 makes first flight, accelerates Hermeus hypersonic program and brings the Mach 5 Halcyon passenger plane project closer.

Hermeus wants to create hypersonic plane with startup pace and goal of one prototype per year

Chimera Engine is the central technology of Quarterhorse and the greatest challenge of hypersonic flight

Quarterhorse sequence was designed to solve each stage of hypersonic flight

Halcyon is the hypersonic passenger plane that Hermeus wants to put in the air before the end of the decade

Investors and the American government bet that Hermeus can change hypersonic aviation

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Four times faster than the Concorde, capable of taking passengers from New York to London in less than an hour at Mach 5.5, and with an engine that switches from turbojet to ramjet mid-flight at Mach 3.5, the Hermeus Quarterhorse went from paper to its first flight in just 19 months.

Quarterhorse Mk 1 makes first flight, accelerates Hermeus hypersonic program and brings the Mach 5 Halcyon passenger plane project closer.

Hermeus wants to create hypersonic plane with startup pace and goal of one prototype per year

Chimera Engine is the central technology of Quarterhorse and the greatest challenge of hypersonic flight

Quarterhorse sequence was designed to solve each stage of hypersonic flight

Halcyon is the hypersonic passenger plane that Hermeus wants to put in the air before the end of the decade

Investors and the American government bet that Hermeus can change hypersonic aviation

A British company has installed in the middle of the ocean the world’s first floating platform that generates electricity 24 hours a day from the temperature difference between the surface and the depths of the Atlantic, without relying on wind or sun.

Great Atlantic Sargassum Belt has ceased to be a climatic phenomenon and has become a biological system that feeds on itself, with 8,000 kilometers in length, 37 million tons of algae, and scientists confirm that it is now permanent.

China is building an artificial island in the middle of the sea, covering 20 km², to construct the largest offshore airport in the world, the Dalian Jinzhouwan. This $4.3 billion project is anchored on more than 3,000 pillars embedded in the rock beneath the ocean and is scheduled to open in 2035.

A robot named Walter does the work of five bricklayers per hour and can save the construction industry, where the average age of professionals is 46 years and almost no one wants to learn the trade anymore, in the United Kingdom.

Austrian engineers have developed an inflatable concrete technology that transforms flat slabs into domes using only air pressure, eliminating scaffolding and temporary forms, and potentially changing the way bridges, tunnels, and curved roofs are constructed worldwide.

Engineers had to pour concrete mixed with tons of ice throughout entire nights in the Dubai desert to erect the Burj Khalifa; any carelessness could clog the pipes half a mile high.

The James Webb telescope spotted a planet 700 light-years from Earth with mornings full of sand clouds and nights with clear skies, the temperature difference between the two hemispheres reaches an impressive 170 degrees.

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