The M51 Skysweeper (Gun, M51, Antiaircraft or Gun automatic, 75-mm T83E6, and E7, recoil mechanism, and loader rammer) was an
anti-aircraft gun
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
deployed in the early 1950s by both the
U.S. Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
and
U.S. Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
. It was the first such gun to combine a
gun laying
A gun is a ranged weapon designed to use a shooting tube (gun barrel) to launch projectiles. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns/cannons, spray guns for painting or pressure washing, p ...
radar,
analog computer
An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (''analog signals'') to model the problem being solved. In c ...
(director) and an
autoloader
An autoloader or auto-loader is a mechanical aid or replacement for the personnel that load ordnance into crew-served weapons without being an integrated part of the gun itself. The term is generally only applied to larger weapons, such as naval ...
on a single carriage.
The Skysweeper was introduced just as
surface-to-air missile
A surface-to-air missile (SAM), also known as a ground-to-air missile (GTAM) or surface-to-air guided weapon (SAGW), is a missile designed to be launched from the ground to destroy aircraft or other missiles. It is one type of anti-aircraft syst ...
s were being deployed in the long-range role, replacing earlier
anti-aircraft artillery
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
systems. These missiles were very large and slow to react, which left short-range engagements to guns. The Army's existing guns were a motley collection of
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
-era systems that were barely effective then, and were considered largely useless against jet-powered aircraft. Missiles replaced all of the larger weapons, while Skysweeper replaced all the smaller ones.
The Skysweeper system was used for a relatively short period of time, from the mid to late 1950s in the US, and into the 1960s and 1970s in some overseas locations. By that time newer missile systems were closing the range gap, and the Army was busy developing new weapons like the
MIM-46 Mauler
The General Dynamics Mauler was a self-propelled anti-aircraft missile system designed to a late 1950s US Army requirement for a system to combat low-flying high-performance tactical fighters and short-range ballistic missiles.
The system was ...
for this role.
Development
Anti-aircraft guns naturally fall into several categories, each for a different
altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
and
speed
In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quanti ...
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
An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an ...
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 40 mm Bofors 40 mm gun is a name or designation given to two models of 40 mm calibre anti-aircraft guns designed and developed by the Swedish company Bofors:
*Bofors 40 mm L/60 gun - developed in the 1930s, widely used in World War II and into the 1990s
...
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
Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the 20th century. Sperry ceased to exist in 1986 following a prolonged hostile takeover bid engineered by Burroughs ...
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
Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...
, 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 square platform with powered traverse, which also mounted the box-shaped 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 kmRADAR EQUIPMENT - SITES & SPECIFICATIONS
by Martin Shough (via the Internet Archive
The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge". It provides free public access to collections of digitized materials, including websites, software applications/games, music, ...
). Accessed 9 July 2008. 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
An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...
(ARAACOM) in the U.S near targets that would have to be attacked by low-altitude aircraft. During the 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
The United States Army's Nike Ajax was the world's first operational guided surface-to-air missile (SAM), entering service in 1954. Nike Ajax was designed to attack conventional bomber aircraft flying at high subsonic speeds and altitudes above ...
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
Sault Ste. Marie ( ') is the only city in, and county seat of, Chippewa County, Michigan, Chippewa County in the U.S. state of Michigan. With a population of 13,337 at the 2020 United States census, 2020 census, it is the second-most populated ...
, to protect the
Soo Locks
The Soo Locks (sometimes spelled Sault Locks but pronounced "soo") are a set of parallel locks, operated and maintained by the United States Army Corps of Engineers, Detroit District, that enable ships to travel between Lake Superior and the lowe ...
(one battalion),
Savannah River Site
The Savannah River Site (SRS) is a U.S. Department of Energy (DOE) 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 August ...
(two), and one 90mm and two Skysweeper battalions at
Thule Air Base
Thule Air Base (pronounced or , kl, Qaanaaq Mitarfik, da, Thule Lufthavn), or Thule Air Base/Pituffik Airport , is the United States Space Force's northernmost base, and the northernmost installation of the U.S. Armed Forces, located north o ...
,
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
(all were removed by 1959). The last overseas Skysweeper were deactivated in the mid-1970s, being wholly replaced by other more advanced anti-air missile systems.
Survivors
* Two Skysweepers are on display at the Air Defense Artillery Museum at
Fort Sill
Fort Sill is a United States Army post north of Lawton, Oklahoma, about 85 miles (136.8 km) southwest of Oklahoma City. It covers almost .
The fort was first built during the Indian Wars. It is designated as a National Historic Landmark ...
, Oklahoma, one in the ADA Park and one at the temporary museum facility.
* A Skysweeper is part of the outdoor exhibit at the
Rock Island Arsenal
The Rock Island Arsenal comprises , located on Arsenal Island, originally known as Rock Island, on the Mississippi River between the cities of Davenport, Iowa, and Rock Island, Illinois. It lies within the state of Illinois. Rock Island ...
Museum in Illinois
* A pair of Skysweepers in varying states of preservation are on display at the Fort Lewis Museum outdoor exhibit at
Joint Base Lewis-McChord
A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw ...
, Washington.
* A pair of Skysweepers are on display outside the gate of Camp Rilea just south of Astoria, Oregon.
* There is a Skysweeper on display outside of the VFW in Elberton, GA.
* One Skysweeper is on display at the International Artillery Museum , St. Jo, Texas.
* One Skysweeper is on display at the American Military Museum, South El Monte, California.
References
External links
*
*{{cite web
, last=Warrell
, first=Kenneth P.
, year=2005
, url=http://www.maxwell.af.mil/au/aul/aupress/Books/Werrell_Archie/Werrell.pdf
, title=Archie to SAM: A Short Operational History of Ground-Based Air Defense
, publisher=Air University Press, Maxwell Air Force Base, Alabama
, accessdate=2006-10-17
, archiveurl=https://web.archive.org/web/20060722111104/http://www.maxwell.af.mil/au/aul/aupress/Books/Werrell_Archie/Werrell.pdf
, archivedate=2006-07-22
, url-status=dead
Anti-aircraft guns of the Cold War
Anti-aircraft guns of the United States
75 mm artillery
Gun laying radars
Military equipment introduced in the 1950s