1997: The Air Force reached a milestone in advanced missile propulsion with the successful ground testing of the Variable Flow Ducted Rocket at Atlantic Research Corp., Gainesville, Va. A solid-fuel, ducted rocket engine, the VFDR increased the capabilities of conventional rockets by burning fuel-rich rocket-exhaust gases with air, thereby doubling or tripling the total energy produced by the engine. (Artist’s Conception of a VFDR missile launch. USAF image)