Duality: the hybrid engine that aims to bring the supersonic dream back to life, at a decent cost.

Is it possible to fly from London to New York in under three hours without spending a small nation's GDP on fuel? A California startup and a British engineering firm are betting it can, thanks to a "chameleon" engine.

Civilian supersonic flight died on the last day Concorde touched down in 2003. It died not from lack of speed, but from a brutal economic law: inefficiency . Concorde was a technological marvel that burned through money (and kerosene) at an unsustainable rate, especially at subsonic speeds, making the ticket affordable only to the financial elite.

Today, however, amid the silence of the mainstream media, an interesting technological marriage is taking place between old England and Silicon Valley. British company Helix , known for its ultra-high-power density electric motors (used in hypercars like the Lotus Evija), has teamed up with American startup Astro Mechanica . The goal? To build Duality , a hybrid-electric propulsion system designed to make flight at Mach 3 not only possible, but economically sustainable.

Not the “usual” jet engine

To understand why this news deserves attention, we need to look under the hood. Most supersonic projects fail because they attempt to marginally improve upon the classic turbojet. Astro Mechanica instead decided to split it in two .

In a conventional jet engine, the turbine that generates power is mechanically connected to the fan that pushes the air. This is a huge constraint: the optimal speed for the turbine is almost never the optimal speed for the fan, especially when transitioning from takeoff to supersonic flight.

The Duality system breaks this bond:

1. The heart: A gas turbine (or turbogenerator) acts only as an electricity generator, running at its constant optimum speed.
2. The muscles: The energy produced powers electric motors (supplied by Helix) that drive the compressor and fan.

This "separation of powers" allows the engine to behave like an aerodynamic chameleon, adapting to three different flight modes. This isn't science fiction; it's applied engineering to solve the problem of marginal efficiency.

Three engines in one: the adaptive cycle

The most intriguing aspect for those interested in industrial efficiency is the engine's ability to change its appearance based on speed. Here's how the "magic" of the combined cycle works:

• Mode 1: Turbofan (Subsonic) During takeoff and low-speed flight, the electric motors drive the fan to move large masses of air at low speed. The result: high efficiency, low noise, and low fuel consumption. This is exactly what the Concorde lacked, which drank like a water pump during takeoff.
• Mode 2: Turbojet (Transonic) As the sound barrier approaches, the system changes configuration.5 Fuel injection and air management transform it into a pure turbojet, ideal for breaking the sound barrier without losing thrust. The turbofan passages are then closed and the air is concentrated in the turbojet.
• Mode 3: Ramjet (Supersonic Mach 3) This is where we enter rocketry territory. At speeds above Mach 2, the engine can virtually "shut down" the complex rotating parts and exploit the dynamic pressure of the incoming air (ram pressure) for combustion.6 No heavy moving parts, just pure thermodynamic thrust.

The numbers: the power of Helix

Without a lightweight, powerful electric motor, this would all be just a nice PowerPoint presentation. This is where Helix comes in. The Milton Keynes-based company supplied the motors for the fourth-generation prototype.

Let's analyze the technical data provided, because, as always, the devil is in the details:

Specification	Current Prototype (Gen 4)	Future Objective (Gen 5)
Electric Motors	4x Helix SPX242-94	Custom Helix Design
Weight per Engine	31.3 kg (69 lbs)	–
Peak Power	400 kW (each)	950 kW
Continuous Power	300 kW	900 kW
Maximum Torque	470 Nm	575 Nm
Rotation Regime	Up to 17,000 rpm	20,000 rpm

Derek Jordanou-Bailey , Helix's chief engineer, emphasized that the unusual power-to-weight ratio of these engines is the only key to managing the "extreme demands" of supersonic airflow. We're talking about engines that weigh as much as a large dog but develop the power of a supercar.

The economic gamble

Why is this project relevant from a macroeconomic perspective? Because Astro Mechanica isn't just targeting speed, but cost per passenger .

The plan calls for using Liquefied Natural Gas (LNG) instead of the expensive Jet A-1.

1. Cost: LNG costs about one-tenth of traditional jet fuel.
2. Energy Density: Offers a higher calorific value, allowing for greater autonomy.
3. Emissions: It burns cleaner (-30% CO2), a significant factor in avoiding the environmental taxes that stifle modern aviation.

The basic idea is purely economic: invest in hard technology to create a new market. If you can take a passenger from San Francisco to Tokyo in four hours for the price of a current business class ticket, you're not just selling a flight, you're changing global logistics and the pace of international trade.

The challenges: not all is gold

Obviously, as good realist observers, we must raise doubts.

• Thermal Management: Running high-powered electric motors at Mach 3 generates infernal heat. Helix has developed a "new engine isolation system" for high altitude, but physics is stubborn. Dissipating heat at those speeds is the real bête noire.
• Integration: Coordinating the turbine, generators, electric motors, and variable airflow requires monstrous control software.
• Batteries vs Generators: The system is “turbo-electric”, thus bypassing the problem of the weight of the batteries (which would never have the energy density for supersonic travel), but adds the complexity of having a flying power plant on board.

Will this be the future?

The Duality project represents the kind of bold engineering that the West seemed to have forgotten in favor of smartphone apps. The combination of British expertise in electric motors and American aerospace ambition could truly unlock civil supersonic flight.

If the Gen 5 prototype delivers on its promise of a sustained 900 kW at 20,000 rpm, we could be looking at the Concorde's spiritual (and economic) heir. For now, let's keep our feet on the ground, but keep our eyes on the speedometer: Mach 3 is a promise of speed, but there's still a long way to go.

Questions and Answers

Why did Concorde fail, and could this project work?

Concorde used pure turbojet engines with afterburners, which were extremely inefficient at low speeds and very noisy. This made operating costs prohibitive and limited its routes. The Duality engine uses a hybrid system that behaves like an efficient turbofan at takeoff (low fuel consumption and noise) and becomes a ramjet at high speed.10 Furthermore, the planned use of Liquefied Natural Gas (LNG) dramatically reduces fuel costs compared to aviation kerosene.11

What does it mean that the engine is “electric” but uses fuel?

It's not a battery-powered aircraft. It's a turbo-electric or series hybrid system. A gas turbine burns fuel (LNG or jet fuel) to generate electricity via a generator. This electricity powers the Helix electric motors that turn the fans and compressors. This decouples power generation from propulsion, allowing each component to spin at its optimal speed, maximizing thermodynamic efficiency, which in traditional engines is compromised by the direct mechanical connection.

When will we see these planes flying?

We're still in the advanced prototyping phase of the engines. Astro Mechanica is testing the "Gen 4" and designing the "Gen 5." Before we see a passenger aircraft, the technology will likely be used on military drones or experimental cargo vehicles. A transpacific demonstration flight could be optimistically completed by the end of the decade, but civil aviation requires a very long certification period. Realistically, paying passengers at Mach 3 won't be seen until the 2030s.

The article Duality: the hybrid engine that wants to bring the supersonic dream back to life, at a decent cost comes from Scenari Economici .

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This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/duality-il-motore-ibrido-che-vuole-riportare-in-vita-il-sogno-supersonico-a-costi-decenti/ on Tue, 02 Dec 2025 08:00:35 +0000.