Electrification and Sustainability, Military

U.S. Army Awards $1.7M Contract to LiquidPiston for Hybrid Electric Engine Development

By Jessica Reed | September 13, 2022
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LiquidPiston was awarded a Phase II contract this week by the U.S. Army to continue development of a propulsion system. A prototype of the Hybrid Electric X-Engine (HEXE) propulsion system is pictured above. (Photo: LiquidPiston)

The U.S. Army just awarded a Phase II contract of $1.7 million to the company LiquidPiston. The contract follows LiquidPiston’s successful completion of a Phase I xTechSearch Small Business Innovation Research (SBIR) award. The company developed and demonstrated a prototype of its Hybrid Electric X-Engine (HEXE) propulsion system two years ago. With the Phase II contract, LiquidPiston will continue to develop the HEXE propulsion system.

The company, based in Connecticut, develops scalable, compact, and efficient combustion engines. LiquidPiston has also received interest from the U.S. Air Force in the form of a Small Business Technology Transfer (STTR) contract worth $150,000, awarded in March of 2021 through the USAF’s Agility Prime program. The investment targeted development of a hybrid-electric propulsion system via LiquidPiston’s X-Engine technology. This technology enables unmanned aircraft to charge batteries while in flight by using fuel to power a generator. LiquidPiston’s X-Engine technology has undergone research and development for over 10 years in collaboration with DARPA, the Army, and industry leaders.

The HEXE propulsion system currently in development will be compatible with military-grade heavy fuels like JP8. The platform is expected to deliver advanced take-off and in-flight capabilities to meet the U.S. Army’s objectives related to vertical take-off and landing (VTOL) aircraft and tactical unmanned aircraft systems (UAS).

A photo comparing a standard 35hp diesel engine, on the left, next to LiquidPiston’s 40hp diesel engine on the right (Photo: LiquidPiston)

Zeke Topolosky from the Strategic Partnerships Office, U.S. Army Combat Capabilities Development Command Army Research Laboratory, commented in the announcement by LiquidPiston, “One of the Army’s major areas of focus for modernization is Future Vertical Lift (FVL). Over the past few years, Army xTech judging panels have repeatedly recognized LiquidPiston’s technological developments in holding great promise for supporting critical Army requirements for FVL modernization. We are pleased to see their efforts advance with this Army Phase II SBIR program.”

LiquidPiston’s hybrid system is being developed to enable up to 30 minutes of all-electric cruising for aircraft, as well as electric-assist “sprint” and “climb” modes. With the HEXE VTOL system, the Army will be able to launch and land aircraft in small areas. Since the system combines electric and engine power on the main propeller shaft, maximum flight velocity is higher during the electric-assist “sprint” mode.

LiquidPiston has patented a High-Efficiency Hybrid Cycle (HEHC) that is utilized in its X-Engine technology. The HEHC enables fuel-energy conversion solutions for hybrid power systems, such as those powering UAS, VTOL aircraft, and auxiliary power units (APUs).

A diagram illustrating LiquidPiston's High-Efficiency Hybrid Cycle, or HEHC (Photo: LiquidPiston)

The founder and CEO of LiquidPiston, Alec Shkolnik, remarked in a statement that there are no diesel engines available today—at least domestically—that are small enough or light enough to be used in unmanned aerial vehicles. “LiquidPiston is primed to address these challenges for the DoD and for broader mobility applications with greater power to weight requirements,” Shkolnik explained.

“Reliable and efficient sources of power and energy for intelligence, surveillance and reconnaissance (ISR), weapons systems, forward operating bases, and other solutions are critical to protecting the warfighter, enhancing warfighting capability, improving fuel efficiency, and reducing logistical burden and operational costs.” 

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