Maker of Small Supercharged Rotary Engine Tapped by USAF for Future Powerplants

LiquidPiston to make engines for the USAF 6 photos
Photo: LiquidPiston
LiquidPiston XTS-210LiquidPiston XTS-210LiquidPiston XTS-210LiquidPiston XTS-210LiquidPiston XTS-210
At the moment, the name LiquidPiston may not mean all that much in this world, but chances are that will change very soon. That's because the Connecticut-based company has set out to effectively reinvent the rotary engine.
The last we heard of these guys was back in April 2023, when they made the XTS-210 rotary engine available for the masses, not only for the American military, which has taken an interest in this new tech.

The XTS-210 is described by its maker as a rotary engine with just two moving parts, the rotor and the shaft. It works like a two-stroke engine, delivering six combustion events per revolution of the rotor.

Technically, the powerplant is scalable, and could offer from one to 1,000 hp, depending on need and application. The tech shown in April is at the bottom of that scale, being capable of developing 25 horsepower.

That may seem tiny by any standard, but you should keep in mind the troop comes from just 210cc of displacement, and from a piece of hardware that's 80 percent smaller and lighter than powerplants of comparable power levels.

That's possible thanks to both supercharging and the use of a technology called High Efficiency Hybrid Cycle (HEHC). As per LiquidPiston, that's a thermodynamic cycle engine design that "combines the advantages of Diesel, Otto and Atkinson," and that results in "up to 30% improved efficiency" and ten times more power.

The engine has been designed primarily with use for power generation and propulsion for VTOLs. The tech is so impressive that the U.S. Army is already looking at the tech for possible use in drones, sea, and air vehicles, either as a primary engine or an auxiliary power unit. For that, the Army awarded LiquidPiston a $9 million contract at the end of last year.

Now the U.S. Air Force (USAF) is joining the Army, as it announced a Strategic Funding Increase "to produce a new class of hybrid power solution and a new engine program based on its X-Engine heavy fuel platform and High Efficiency Hybrid Cycle (HEHC) optimized thermodynamic cycle."

The funding increase means the company could receive up to $15 million, with the powerplants resulting from the increase to be used for both ground and airborne applications.

Neither party said when are we to expect a real-life application of the technology, but given America's drive to modernize its arsenal, but also the push to become more fuel efficient and less harmful to the environment, we expect the tech to be tested and adopted quite rapidly.

How rapidly? Word is the U.S. Army will get its hands on the first LiquidPiston engines at as soon as next year. So far, we know of no civilian application for the tech.
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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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