The Little Engine That Could… Be Carried Into Battle

LiquidPiston’s compact rotary engine to power the U.S. Army’s portable power generators.

Which would you rather carry into battle? Liquid Piston’s XTS-210 engine core compared to 25 hp Kohler KDW1003. Image: LiquidPiston

Soldiers in hostile territory have one question in common with civilians in new surroundings: Where do I plug this in? “This” can refer to mobile radios, night vision goggles, satellite connections—a host of electronics that all need to be charged. In addition, there’s the need to heat coffee, keep the lights on, provide warmth—and, as is occurring in Ukraine’s battlefield, with no help from a bombed-out power grid. If a fighting force’s need for power is critical now, with things like radar, communications and medical equipment, future warriors’ needs will be insatiable. Directed energy weapons (colloquially, ray guns), which are already in development, will require thousands of watts. Forget food, the modern army marches on its power.

Carrying the engine of a 10kW generator in a rucksack—even a downsized one—may be too much for an already overburdened infantry soldier. The weight that a soldier is expected to carry into battle has grown. From ancient times to the American Civil War, all a soldier had to carry weighed 40 pounds. That jumped to 60 pounds in World War I. In the Granada skirmish, soldiers’ gear weighed in at 120 pounds. Today, a U.S. Marine is expected to be able to carry a load of 152 pounds for 9 miles while doing 20-minute miles¹. So, why not carry a generator, if not whole, then in parts?

If you are thinking of your grandpa’s generator, a coughing sputtering beast that would have to be rolled onto the battlefield on a truck, trailer or forklift, think again. The U.S. Army will soon have a new compact genset that weighs only 75 percent as much as the old diesel genset.

We first heard of LiquidPiston’s rotary engines in
2021. Since then, the Connecticut-based company has found favor with the U.S. military, receiving a total of $30 million in defense contracts. LiquidPiston’s XTS-210 engine, about the size of a basketball and a quarter the weight of diesel generators engine, produces just as much power (10kW).

LiquidPiston’s XTS-210 rotary engine delivers 25 HP in a quarter of the weight of a diesel engine.

LiquidPiston will be selling $8.3 million worth of XTS-210 rotary engines to Polaris Alpha Advanced Systems, a Parsons Company, in support of a $14.9 million Other Transaction Authority (OTA) prime contract for U.S. Army Expeditionary Intelligent Tactical and Expeditionary Power awarded by the Department of Defense Ordnance Technology Consortium (DOTC) in 2022. Since 2021, LiquidPiston has amassed over $20 million of Department of Defense contracts. 

“The LiquidPiston generator set (genset) will be approximately one-quarter the size and weight of the currently fielded Advanced Medium Mobile Power Source (AMMPS) generator system,” according to LiquidPiston in its announcement. “Given its smaller footprint and inverter type operation, LiquidPiston’s new genset could replace multiple existing generator power classes with a single genset platform, greatly simplifying Army genset procurement and logistics.”

Not only does the LiquidPiston rotary engine offer portability, but it also operates using 8 percent less fuel. The overburdened infantry soldier, now carrying generator parts, can take heart in saving the lives of fuel supply drivers. Fuel trucks were the favorite targets of roadside bombs in Middle East conflicts. Half of the fatalities suffered by U.S. forces in Iraq and 40 percent of those in Afghanistan were due to attacks on fuel convoys, according to a Deloitte study².

LiquidPiston hopes to parlay its success with the military into success in the consumer marketplace, which Alec Shkolnik, cofounder and CEO of LiquidPiston, sees as a $4 billion global portable generator market.”

Corrected: October 5, 2023. Changed from “three quarters the weight” to “a quarter the weight.”