By U.S. ArmyApril 26, 2019
Developed after World War II, the Skysweeper is equipped with radar and a computer, allowing the gun's operators to spot, track, and intercept low-flying, high-speed enemy aircraft. The loader-rammer, a complicated mechanism used to feed and eject shells in the Skysweeper, was manufactured at Rock Island Arsenal in 1955. It has a rate of fire of 45 rounds per minute.
Before Air Defense Missiles
With the ever changing technology of aeronautics, the U.S. found itself needing a system that would track high-altitude and high-speed jet aircraft following World War II. The successful supersonic flight of the Bell X-1, coupled with the altitude capabilities of the Convair B-36 Peacemaker, led the Army to correctly believe that the future required anti-aircraft defenses that would track faster and higher flying aircraft. The Army was able to offset the issue at higher altitudes with larger gun, which would later be supplemented with high-speed missiles. Low altitude aircraft could be handled by turret guns. However, the midrange between 20,000 and 40,000 feet was ill defended.
The M51 Skysweeper was developed with these requirements in mind. Fitted with a radar system and a computer, the M51 was capable of tracking enemy aircraft at speeds of up to 700 miles per hour and altitudes of up to 43,000 feet. The T-38 radar system fitted to the Skysweeper was capable of detecting aircraft over 23 miles away. The fastest American fighter at the time the M51 was activated was the F-86 Sabre, at 687 miles per hour. By comparison, the Russian MiG-15 traveled at 667 miles-per-hour.
The M51 served for a relatively short period of time, as it was quickly made obsolete by the fast evolving technology of missile systems like the Nike. The evolution of aircraft technology also increased the maximum speed of aircraft. By 1953, the F-100 Super Sabre produced speeds of 863 miles per hour, with subsequent aircraft achieving higher speeds. The 1959 Russian MiG-21 "Fishbed" was capable of speeds of 1,384 miles per hour. By the late 1950s, the Skysweeper had begun to be phased out, with all units deactivated by the early 1970s.