Weird Combustion Science

Popular Mechanics, a source we seldom cite, reports on a rotary engine, a little like the Wankel but better, which has won a DARPA contract. Check out the comparison:

A typical 3kW gasoline-powered generator—the type used at construction sites and as a stop-gap during power outages—weighs about 140 pounds and measures about 3 feet long, 2 feet high, and 2 feet wide. The military uses such generators in remote areas, but they are ungainly beasts. Shkolnik says LiquidPiston's equally powerful generator using JP-8 would weigh about 30 pounds (the motor itself would weigh just 8 pounds) and fit in a backpack.

It is a sort of diesel, firing on compression and requiring no spark. They also believe, at least in smaller sizes, it won't require a cooling jacket and radiator. One of these could turn a bicycle into a motorcycle easily, or power a chainsaw or lawnmower.