The Defense Advanced Research Projects Agency (DARPA) announced today the first-ever successful free flight of a hypersonic projectile powered by a supersonic combustion ramjet (scramjet) engine burning hydrocarbon fuel. The projectile is a four-inch diameter, 20-percent scale model of a conceptual missile. Scramjet engines provide propulsion at speeds above Mach 5 by capturing atmospheric air to burn on-board fuel. These air-breathing engines are more efficient than rocket motors for hypersonic propulsion, and will ultimately allow the possibility of longer duration flight with greater payload.