Capt. Yongjun Yoon, an RF sensing engineer from the RF Technology Branch at AFRL's Sensors Directorate, and David Sobota, with the Sensors Effects and Analysis Branch, in front of a ZPU-4 Soviet-built anti-aircraft gun at the National Museum of the United States Air Force. Composed of four KPV 14.5mm heavy machine guns mounted on a four-wheel carriage, the ZPU-4 was used by the Iraqis in 1991 during Operation Desert Storm. The effective range for the anti-aircraft gun was approximately 5,000 feet (1,500 meters). Each gun had a muzzle velocity of approximately 3,300 feet/second (990 meters/second) and a rate of fire of 600 rounds per minute. The metal link belt contained 100 rounds for each gun. The Air Force Research Lab is mostly interested in the longer range, more lethal AAA guns for research. (U.S. Air Force photo)