Skysweeper was an
anti-aircraft gunNATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...
deployed in the early 1950s by both the
U.S. ArmyThe United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
and
U.S. Air ForceThe United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
. It was the first such gun to combine a
gun layingGun laying is the process of aiming an artillery piece, such as a gun, howitzer or mortar on land or at sea against surface or air targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights...
radar,
M10 analog computer (director)A director, also called an auxiliary predictor, is a mechanical or electronic computer that continuously calculates trigonometric firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew....
, and an
autoloaderAn autoloader or auto-loader is a mechanical aid or replacement for the personnel that load ordnance into crew-served weapons, such as tanks and artillery...
on a single carriage.
Development
Anti-aircraft guns naturally fall into several categories, each for a different
altitudeAltitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
and
speedIn kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
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
airlinerAn airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...
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 WWII 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 velocityMuzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns...
, 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 and
Korean WarThe Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...
field units used the system primarily for airbase defense. Skysweeper was also part of the Army's Anti-Aircraft Command (ARAACOM) in the U.S near targets that would have to be attacked by low-altitude aircraft.
Army Anti-Aircraft Command: During 1950 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, MichiganSault Ste. Marie is a city in and the county seat of Chippewa County in the U.S. state of Michigan. It is in the north-eastern end of Michigan's Upper Peninsula, on the Canadian border, separated from its twin city of Sault Ste. Marie, Ontario, by the St. Marys River...
, to protect the
Soo LocksThe Soo Locks are a set of parallel locks which enable ships to travel between Lake Superior and the lower Great Lakes. They are located on the St. Marys River between Lake Superior and Lake Huron, between the Upper Peninsula of the US state of Michigan and the Canadian province of Ontario...
(one battalion),
Savannah River SiteThe Savannah River Site is a nuclear reservation in the United States in the state of South Carolina, located on land in Aiken, Allendale and Barnwell Counties adjacent to the Savannah River, southeast of Augusta, Georgia. The site was built during the 1950s to refine nuclear materials for...
(two), and one 90mm and two Skysweeper battalions at
Thule Air BaseThule Air Base or Thule Air Base/Pituffik Airport , is the United States Air Force's northernmost base, located north of the Arctic Circle and from the North Pole on the northwest side of the island of Greenland. It is approximately east of the North Magnetic Pole.-Overview:Thule Air Base is the...
,
GreenlandGreenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
(all were removed by 1959). Skysweeper was found in various places until the early 1970s.
Survivors
- A Skysweeper is on display at the Air Defense Artillery Museum at Fort Bliss
Fort Bliss is a United States Army post in the U.S. states of New Mexico and Texas. With an area of about , it is the Army's second-largest installation behind the adjacent White Sands Missile Range. It is FORSCOM's largest installation, and has the Army's largest Maneuver Area behind the...
, Texas
General characteristics
- Caliber: 75 mm
- Barrel length: 4,500 mm (60 caliber)
- Magazine: 2 × 10 rounds
- Maximum range: 13.5 km
- Effective range: 6.3 km