Quarterhorse aims to revive supersonic flight Mk1
It has been over 20 years since the retirement of the Concorde - the last and one of only two large passenger jet aircraft in history. Many companies desire to build an improved successor, but little has been accomplished so far. The situation might change with the Quarterhorse – a hypersonic passenger plane technology demonstrator.
Hypersonic vehicles are commonly associated with weapons – gliding or propulsion-driven objects designed to overcome modern, increasingly sophisticated air defence systems due to high speeds.
This association is due to their high speeds—reaching approximately Mach 5 and above—and their manoeuvrability capabilities. These features differentiate modern hypersonic weapons from, for instance, intercontinental ballistic missiles.
While these descend on targets at extremely high speeds (over 20,000 km/h), they move along predictable, calculable ballistic curves, making them easier to destroy.
This is why the world's greatest powers are developing hypersonic weapons. Due to the advancement of work and the creation of declared equipment features, China and Russia are considered leaders. The United States, with constructions like the AGM-183A ARRW, is closing the gap, and France is also developing its hypersonic missile, the ASN4G.
Hypersonic vehicles, in addition to being associated with innovative weapons, offer breakthrough potential in civil applications. One example is the development of an ultra-fast mode of transportation that significantly reduces travel time over long distances. Work on this has progressed beyond the conceptual and design phases.
Concorde and Tu-144
For years, the Concorde was a symbol of fast passenger transport. It was developed in the 1960s by the French company Aérospatiale and the British BAE.
The Concorde reached a speed of Ma 2.04 (about 2,205 km/h), ascended to 18,000 metres, carried up to 128 passengers, and allowed for flights over distances exceeding 7,000 kilometres, which was enough to conduct regular transatlantic flights between Europe and the United States.
What distinguished the Concorde was not only its maximum speed but also its ability to maintain high flight speeds for prolonged periods. Because of this, even theoretically faster military aircraft like the Tornado could only accompany the Concorde for a short time, as flying at such high speeds quickly drained their fuel tanks.
Alongside the Concorde, passenger flights were also served by its eastern competitor, sometimes called the "Konkordski" – the Russian Tu-144 aircraft. High failure rates and operating costs led to these machines being retired from scheduled flights as early as the 1970s.
The Concorde continued to serve passenger flights until 2003. The retirement of this type of aircraft followed an accident involving one of the planes, but the key reason was the very high costs, which made further operation unprofitable. The retirement of the Concorde means that for over 20 years, mass passenger air transport has been served by subsonic machines.
Quarterhorse Aircraft
Although a successor to the Concorde has not yet been built, constructions are emerging aimed at testing technical solutions and verifying ideas for developing a new hypersonic passenger aircraft.
According to its originator, Hermeus from Atlanta, the trip from Europe to New York will take no more than 90 minutes. The aircraft is supposed to be a groundbreaking construction that will allow for fast travel and change the nature of global passenger transportation by offering previously unattainable possibilities.
Will this be the case? The opportunity to verify this claim is approaching quickly, as Hermeus has announced the completion of the flying demonstrator of the hypersonic Quarterhorse aircraft.
The project to build the ultimate hypersonic passenger machine is being realized in stages, marked by the completion of successive experimental, unmanned constructions. The first of them, Quarterhorse Mk 0, had no flight capability and was created to test onboard installations on the ground.
The second prototype—completed in December 2024, the Quarterhorse Mk 1—is currently being tested on the ground but is expected to take flight in 2025. It will fly at subsonic speeds, primarily for take-off and landing tests. The plan is for another flying prototype, the Quarterhorse Mk 2, powered by the F100 engine from the F-16 fighter jet, to reach supersonic speeds in 2025.
An aircraft with a ramjet engine
Only the Quarterhorse Mk 3, whose first flight is planned for 2026, will receive the ultimate Chimera II propulsion. It combines the F100 engine with a scramjet (a ramjet engine with a supersonic combustion chamber).
A hybrid propulsion system is necessary because the aircraft must be accelerated to high supersonic speeds to activate the ramjet. Hermeus anticipates that the Quarterhorse Mk 3 will reach Mach 5 speeds—around 6,000 km/h—allowing it to be classified as a hypersonic machine.
Successors to the Concorde
Tests conducted on a series of unmanned aircraft are expected to contribute to developing a military hypersonic aircraft, Darkhorse, and subsequently, the ultimate passenger aircraft, Halcyon, which can carry up to 20 passengers. Hermeus anticipates that commercial flights of this construction will begin as soon as 2029.
Even if this optimistic schedule is maintained, Hermeus will not be a monopolist. Though an attempt to build a supersonic passenger aircraft buried the Aerion Corporation several years ago, companies like Boom Technology are working on similar machines. The Boom XB-1 demonstrator will fly in March 2024.
Exosonic is also developing a successor to the Concorde. Its large passenger machine is being considered a future platform for Air Force One. In November 2024, the Chinese company Lingkong Tianxing Technology also revealed work on the supersonic passenger aircraft Cuantianhou.
