The military may be downsizing its internal combustion engines significantly in some applications following reports that DARPA has offered a million-dollar contract to LiquidPiston to develop its power-dense rotary engine for small-engine applications.

EngineLabs took a quick look at this unique technology by spotlighting a 70cc rotary engine late last year. Only a little bigger than an iPhone and weighing about three pounds, the engine makes five horsepower at 15,000 rpm.

According to a company news release, the agreement with the US Defense Advance Research Projects Agency (DARPA) is worth $991,557. LiquidPiston will use to the funds to advance development of the engine for portable applications, such as field generators or unmanned aircraft. LiquidPiston will also work towards adapting the engine to JP-8 fuel, which is a kerosene-based jet fuel that powers aircraft, helicopters and tanks. The military has long set a goal of adapting all IC engines, including diesels in cargo and troop transport as well as the HMMWVs, to running on JP-8. Such a move would dramatically reduce costs and logistical problems of handling two types of fuel in combat zones.

“Today’s diesel/JP-8 engines and generators are extremely heavy. For example, a typical 3kW heavy-fuel generator weighs over 300 pounds, requiring six people to move it around,” explains company founder Dr. Kniolay Shkolnik. “LiquidPiston’s engine technology may enable a JP-8 generator of similar output weighing less than 30 pounds that could fit in a backpack.”

LiquidPiston says early prototypes have confirmed compression ignition of diesel and JP-8 fuels. The company built 70-horsepower and 40-horsepower compression ignition, heavy-fuel engine alpha prototypes. The ultimate goal of the funded effort is to demonstrate a pathway to a heavy-fueled engine that could deliver above 50 percent average brake efficiency, 57 percent peak brake efficiency and high power density of more than one horsepower per pound in a test-bed environment.