Skysweeper Skysweeper ( Gun , M51 , Antiaircraft or D48 Gun automatic , 75 - mm T83E6 , and E7 , recoil mechanism , and loader rammer ) was an anti - aircraft gun deployed in the early 1950s by both the U . S . Army and U . S . Air Force . It was the first such gun to combine a gun laying radar , director , and an autoloader on a single carriage . Development . Anti - aircraft guns naturally fall into several categories , each for a different altitude and speed requirement . High - altitude targets require very large guns to get the needed power into the shell to reach those altitudes , but at the same time have the advantage of not needing to move very fast because at that range the change in angle of the target was small — consider the seemingly slow motion of an airliner at cruise altitude . At very low altitudes there were only seconds in which to react when spotting an aircraft over local terrain , so a hand - swung weapon was the only possibility , no matter how inaccurate . However , the short ranges meant that accuracy was not needed , nor was a large gun needed to cover the range . This left an intermediate altitude at which a small gun could not be used because the range to the aircraft was too far , and a larger gun could not be used because the targets were moving too fast . During World War II this niche had been covered by the Bofors 40mm and similar weapons , but against modern jet - powered aircraft these were effectively useless because they simply didn ' t have the speed and weight of fire to be effective against targets that would be within range for only seconds . This led to the need for a new gun to address this intermediate - range role , and the Army defined this to be a weapon able to defeat aircraft flying at 1 , 000 mph ( 1 , 600 km / h ) at altitudes up to 20 , 000 feet ( 6 km ) . The Sperry Gyroscope Company developed the radar and computer , and development of what would become the Skysweeper started in 1948 . A new 75 mm gun , known as the T83E1 or M35 , was developed that had excellent muzzle velocity , along with two ten - round revolver - type magazines and an auto - loader that allowed it to reach 45 rounds / minute — about one third of what the much lighter Bofors had managed . This was mounted on a large box - shaped powered traverse , which also mounted the computer and manual gunsights on the right side , and the T - 38 radar unit on the left . The T - 38 radar had a range of about 30 km and could track aircraft traveling at up to 700 mph ( 1100 km / h ) . The Army publicly announced the Skysweeper system in the Spring of 1953 . Deployment . Skysweeper deployment began in the early 1950s . Skysweeper was also part of the Army Anti - Aircraft Command ( ARAACOM ) in the U . S near targets that would have to be attacked by low - altitude aircraft . During 1950s the Army formed the Army Anti - Aircraft Command ( ARAACOM ) to operate batteries of anti - aircraft guns and missiles . Most ARAACOM deployments were around cities and used the 90 mm and 120 mm guns , as well as the Nike Ajax missile defense . In 1957 , ARAACOM was renamed to US Army Air Defense Command ( USARADCOM , ARADCOM in 1961 ) and , ARAACOM started to dramatically replace gun sites with fewer missile sites ( ARADCOM ended in 1975 ) . By the end of 1957 Skysweeper battalions remained at Sault Ste . Marie , Michigan , to protect the Soo Locks ( one battalion ) , Savannah River Site ( two ) , and one 90mm and two Skysweeper battalions at Thule Air Base , Greenland ( all were removed by 1959 ) . Skysweeper was found in various places until the early 1970s .