It's been almost a year and a half since we first reported on the U.S. Navy's plans to produce cheap liquid fuel from seawater. And as a proof of concept, the unmodified two-stoke engine in this P-51 Mustang remote control model plane was recently powered using the new liquid fuel instead of traditional gas.

The new type of fuel—known as a liquid hydrocarbon—is created by extracting both carbon dioxide and hydrogen from regular old seawater, and then re-combining them using a proprietary gas-to-liquid process.

But why use dirty seawater instead of the crystal clear H2O you can get in a bottle? It turns out that the concentration of CO2 in the earth's oceans is about 140 times greater than it is in the air. So it's easier and cheaper to extract using machinery no larger than a compact car. Which means that one day the U.S. Navy's entire fleet could have a nearly endless supply of fuel as long as the planet's oceans didn't dry up. [U.S. Naval Research Laboratory via]