Semi-Automatic Ground Environment

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Short description: Historic US military computer and radar network
This article is about the NORAD Cold War computer network. For the radar installations in each sector, see SAGE radar stations.
Semi-Automatic Ground Environment
The 4-story SAGE blockhouses with 3.5 acres (1.4 ha) of floor space[1] "were hardened [for] overpressures of" 5 psi (34 kPa).[2]: 264  A shorter adjoining building (left) had generators below the 4 intake/exhaust structures on the roof.[3] (DC-01 shown)
General information
Typemilitary C3 human–computer interface
CountryUnited States
Opened1958 June 26 — DC-01
1958 December 1 — DC-03
1959 (early) — CC-01
1966 April 1 — CC-05
Design and construction
ArchitectUSAF Air Materiel Command
Western Electric[4]
System Development Corporation[4]
Burroughs Corporation

The Semi-Automatic Ground Environment (SAGE) was a system of large computers and associated networking equipment that coordinated data from many radar sites and processed it to produce a single unified image of the airspace over a wide area.[5] SAGE directed and controlled the NORAD response to a possible Soviet air attack, operating in this role from the late 1950s into the 1980s. Its enormous computers and huge displays remain a part of Cold War lore, and after decommissioning were common props in movies such as Dr. Strangelove and Colossus, and on science fiction TV series such as The Time Tunnel.

The processing power behind SAGE was supplied by the largest discrete component-based computer ever built, the AN/FSQ-7, manufactured by IBM. Each SAGE Direction Center (DC) housed an FSQ-7 which occupied an entire floor, approximately 22,000 square feet (2,000 m2) not including supporting equipment. The FSQ-7 was actually two computers, "A" side and "B" side. Computer processing was switched from "A" side to "B" side on a regular basis, allowing maintenance on the unused side. Information was fed to the DCs from a network of radar stations as well as readiness information from various defense sites. The computers, based on the raw radar data, developed "tracks" for the reported targets, and automatically calculated which defenses were within range. Operators used light guns to select targets on-screen for further information, select one of the available defenses, and issue commands to attack. These commands would then be automatically sent to the defense site via teleprinter.

Connecting the various sites was an enormous network of telephones, modems and teleprinters. Later additions to the system allowed SAGE's tracking data to be sent directly to CIM-10 Bomarc missiles and some of the US Air Force's interceptor aircraft in-flight, directly updating their autopilots to maintain an intercept course without operator intervention. Each DC also forwarded data to a Combat Center (CC) for "supervision of the several sectors within the division"[6] ("each combat center [had] the capability to coordinate defense for the whole nation").[7]: 51 

SAGE became operational in the late 1950s and early 1960s at a combined cost of billions of dollars. It was noted that the deployment cost more than the Manhattan Project—which was ironic, given its role in deterrence of the same type of weaponry that the Manhattan Project had introduced to the world. Throughout its development, there were continual concerns about its real ability to deal with large attacks, and the Operation Sky Shield tests showed that only about one-fourth of enemy bombers would have been intercepted.[8] Nevertheless, SAGE was the backbone of NORAD's air defense system into the 1980s, by which time the tube-based FSQ-7s were increasingly costly to maintain and completely outdated. Today the same command and control task is carried out by microcomputers, based on the same basic underlying data.

Background

Earlier systems

Just prior to World War II, Royal Air Force (RAF) tests with the new Chain Home (CH) radars had demonstrated that relaying information to the fighter aircraft directly from the radar sites was not feasible. The radars determined the map coordinates of the enemy, but could generally not see the fighters at the same time. This meant the fighters had to be able to determine where to fly to perform an interception but were often unaware of their own exact location and unable to calculate an interception while also flying their aircraft.

SAGE radar stations were grouped by Air Defense Sectors (Air Divisions after 1966). The SAGE System networked the radar stations in over 20 of the sectors using AN/FSQ-7 centrals in Direction Center.

The solution was to send all of the radar information to a central control station where operators collated the reports into single tracks, and then reported these tracks to the airbases, or sectors. The sectors used additional systems to track their own aircraft, plotting both on a single large map. Operators viewing the map could then see what direction their fighters would have to fly to approach their targets and relay that simply by telling them to fly along a certain heading or vector. This Dowding system was the first ground-controlled interception (GCI) system of large scale, covering the entirety of the UK. It proved enormously successful during the Battle of Britain, and is credited as being a key part of the RAF's success.

The system was slow, often providing information that was up to five minutes out of date. Against propeller driven bombers flying at perhaps 225 miles per hour (362 km/h) this was not a serious concern, but it was clear the system would be of little use against jet-powered bombers flying at perhaps 600 miles per hour (970 km/h). The system was extremely expensive in manpower terms, requiring hundreds of telephone operators, plotters and trackers in addition to the radar operators. This was a serious drain on manpower, making it difficult to expand the network.

The idea of using a computer to handle the task of taking reports and developing tracks had been explored beginning late in the war. By 1944, analog computers had been installed at the CH stations to automatically convert radar readings into map locations, eliminating two people. Meanwhile, the Royal Navy began experimenting with the Comprehensive Display System (CDS), another analog computer that took X and Y locations from a map and automatically generated tracks from repeated inputs. Similar systems began development with the Royal Canadian Navy, DATAR, and the US Navy, the Naval Tactical Data System. A similar system was also specified for the Nike SAM project, specifically referring to a US version of CDS,[9] coordinating the defense over a battle area so that multiple batteries did not fire on a single target. All of these systems were relatively small in geographic scale, generally tracking within a city-sized area.

Valley Committee

Whirlwind computer elements: core memory (left) and operator console
Module from a SAGE
The RCA #6499 Radechon tube was used for random-access memory in the computers.

When the Soviet Union tested its first atomic bomb in August 1949, the topic of air defense of the US became important for the first time. A study group, the "Air Defense Systems Engineering Committee", was set up under the direction of Dr. George Valley to consider the problem and is known to history as the "Valley Committee".[10]

Their December report noted a key problem in air defense using ground-based radars. A bomber approaching a radar station would detect the signals from the radar long before the reflection off the bomber was strong enough to be detected by the station. The committee suggested that when this occurred, the bomber would descend to low altitude, thereby greatly limiting the radar horizon, allowing the bomber to fly past the station undetected. Although flying at low altitude greatly increased fuel consumption, the team calculated that the bomber would only need to do this for about 10% of its flight, making the fuel penalty acceptable.[10]

The only solution to this problem was to build a huge number of stations with overlapping coverage. At that point the problem became one of managing the information. Manual plotting was ruled out as too slow, and a computerized solution was the only possibility. To handle this task, the computer would need to be fed information directly, eliminating any manual translation by phone operators, and it would have to be able to analyze that information and automatically develop tracks.[10] A system tasked with defending cities against the predicted future Soviet bomber fleet would have to be dramatically more powerful than the models used in the NTDS or DATAR.[11][12]

The Committee then had to consider whether or not such a computer was possible. The Valley Committee was introduced to Jerome Wiesner, associate director of the Research Laboratory of Electronics at MIT. Wiesner noted that the Servomechanisms Laboratory had already begun development of a machine that might be fast enough. This was the Whirlwind I, originally developed for the Office of Naval Research[13] as a general purpose flight simulator that could simulate any current or future aircraft by changing its software.[10]

Wiesner introduced the Valley Committee to Whirlwind's project lead, Jay Forrester, who convinced him that Whirlwind was sufficiently capable. In September 1950, an early microwave early-warning radar system at Hanscom Field was connected to Whirlwind using a custom interface developed by Forrester's team. An aircraft was flown past the site, and the system digitized the radar information and successfully sent it to Whirlwind. With this demonstration, the technical concept was proven. Forrester was invited to join the committee.[10]

Project Charles

With this successful demonstration, Louis Ridenour, chief scientist of the Air Force, wrote a memo stating "It is now apparent that the experimental work necessary to develop, test, and evaluate the systems proposals made by ADSEC will require a substantial amount of laboratory and field effort."[10] Ridenour approached MIT President James Killian with the aim of beginning a development lab similar to the war-era Radiation Laboratory that made enormous progress in radar technology. Killian was initially uninterested, desiring to return the school to its peacetime civilian charter. Ridenour eventually convinced Killian the idea was sound by describing the way the lab would lead to the development of a local electronics industry based on the needs of the lab and the students who would leave the lab to start their own companies. Killian agreed to at least consider the issue, and began Project Charles to consider the size and scope of such a lab.[14]

Project Charles was placed under the direction of Francis Wheeler Loomis and included 28 scientists, about half of whom were already associated with MIT. Their study ran from February to August 1951, and in their final report they stated that "We endorse the concept of a centralized system as proposed by the Air Defense Systems Engineering Committee, and we agree that the central coordinating apparatus of this system should be a high-speed electronic digital computer."[14] The report went on to describe a new lab that would be used for generic technology development for the Air Force, Army and Navy, and would be known as Project Lincoln.[14]

Project Lincoln

Loomis took over direction of Project Lincoln and began planning by following the lead of the earlier RadLab. By September 1951, only months after the Charles report, Project Lincoln had more than 300 employees. By the end of the summer of 1952 this had risen to 1300, and after another year, 1800. The only building suitable for classified work at that point was Building 22, suitable for a few hundred people at most, although some relief was found by moving the non-classified portions of the project, administration and similar, to Building 20. But this was clearly insufficient space. After considering a variety of suitable locations, a site at Laurence G. Hanscom Field was selected, with the groundbreaking taking place in 1951.[14]

The terms of the National Security Act were formulated during 1947, leading to the creation of the US Air Force out of the former US Army Air Force. During April of the same year, US Air Force staff were identifying specifically the requirement for the creation of automatic equipment for radar-detection which would relay information to an air defence control system, a system which would function without the inclusion of persons for its operation.[15] The December 1949 "Air Defense Systems Engineering Committee" led by Dr. George Valley had recommended computerized networking[11] for "radar stations guarding the northern air approaches to the United States"[12] (e.g., in Canada). After a January 1950 meeting, Valley and Jay Forrester proposed using the Whirlwind I (completed 1951) for air defense.[16] On August 18, 1950, when the "1954 Interceptor" requirements were issued, the USAF "noted that manual techniques of aircraft warning and control would impose "intolerable" delays"[17]: 484  (Air Materiel Command (AMC) published Electronic Air Defense Environment for 1954 in December .)[18] During February–August 1951 at the new Lincoln Laboratory, the USAF conducted Project Claude which concluded an improved air defense system was needed.Lua error: Internal error: The interpreter has terminated with signal "24".

Further reading

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  1. ↑ The SAGE Blockhouse - Future Home of the Cold War / Peace Museum . Coldwarpeacemuseum.org. Retrieved on 2013-09-18.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Cite error: Invalid <ref> tag; no text was provided for refs named Schaffel
  3. ↑ 3.0 3.1 3.2 Cite error: Invalid <ref> tag; no text was provided for refs named EdwardsBenj
  4. ↑ 4.0 4.1 4.2 Cite error: Invalid <ref> tag; no text was provided for refs named IYD
  5. ↑ Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 232. ISBN 9780850451634. 
  6. ↑ 6.0 6.1 Cite error: Invalid <ref> tag; no text was provided for refs named Intro
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Winkler
  8. ↑ Mola, Roger A. (March 2002). "This Is Only a Test". Air & Space Magazine. http://www.airspacemag.com/history-of-flight/this-is-only-a-test-3119878/. 
  9. ↑ Nelson, Maj Gen Morris R. (June 12, 1950). subj: Employment of an American Version of CDS. USAFHRC microfilm.  (cited by Schaffel pdf p. 311)
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 "The Valley Committee". 1995. https://www.ll.mit.edu/about/History/origins.html. 
  11. ↑ 11.0 11.1 Quarterly Progress Report (Report). Lincoln Laboratories. June 1952.  (cited by Schaffel p. 197)
  12. ↑ 12.0 12.1 "Physicist George Valley Jr. is dead at 86" (MITnews webpage). MIT Tech Talk. October 20, 1999. http://web.mit.edu/newsoffice/1999/valley-1020.html. 
  13. ↑ "Project Whirlwind is a high-speed computer activity sponsored at the Digital Computer Laboratory, formerly a part of the Servomechanisms Laboratory, of the Massachusetts Institute of Technology (MIT) by the US Office of Naval Research (ONR) and the United States Air Force. IEEE Computer Society". https://www.computer.org/csdl/proceedings-article/afips/1951/50400070/12OmNBvkdmJ. 
  14. ↑ 14.0 14.1 14.2 14.3 "Project Charles". 1995. https://www.ll.mit.edu/about/History/projectcharles.html. 
  15. ↑ 15.0 15.1 Kent C. Redmond; Thomas M. Smith (2000). From Whirlwind to MITRE: The R&D Story of the SAGE Air Defense Computer. MIT Press. ISBN 978-0-262-26426-6. https://books.google.com/books?id=dxZVbxcf_IoC. (20th of April 1951 - p.1, National Security Act 1947 - p.12, April 1947 - p.13)
  16. ↑ "The Many Careers of Jay Forrester". https://www.technologyreview.com/2015/06/23/167538/the-many-careers-of-jay-forrester/. 
  17. ↑ Futrell, Robert Frank (June 1971). Ideas, Concepts, Doctrine: A History of Basic Thinking in the United States Air Force 1907–1964 (Report). 1. Aerospace Studies Institute, Air University.  (cited by Volume I p. 187)
  18. ↑ McRee, Lua error: Internal error: The interpreter has terminated with signal "24". (15 December 1950). …Electronic Air Defense Environment for 1954 (Report). Headquarters, Air Materiel Command. 
  19. ↑ Lapp; Alsop (March 21, 1953). "We Can Smash the Red A-Bombers". Saturday Evening Post: p. 19.  (citation 29 of Volume I, p. 25)
  20. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Pugh
  21. ↑ 21.0 21.1 Cite error: Invalid <ref> tag; no text was provided for refs named VolumeI
  22. ↑ 22.0 22.1 22.2 Cite error: Invalid <ref> tag; no text was provided for refs named RedmondSmith
  23. ↑ quote from Schaffel p. 191; Condit p. 259 footnote 1 cites: "CCS 381 US (5-23-46) sec 37."
  24. ↑ McVeigh, D. R. (January 1956). The Development of the Bomarc Guided Missile 1950–1953 (Report). Western Air Development Center.  (cited by Volume I p. 108 footnote 69: "Before the end of 1953, it was also decided that the Sage system being developed by Lincoln Laboratories would be used to control the Bomarc.69")
  25. ↑ 25.0 25.1 Cite error: Invalid <ref> tag; no text was provided for refs named Condit
  26. ↑ 26.0 26.1 26.2 26.3 26.4 26.5 Cite error: Invalid <ref> tag; no text was provided for refs named NORAD1958B
  27. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lincoln Laboratory
  28. ↑ "MIT Lincoln Laboratory: History:Early Digital Computing (continued)". https://www.ll.mit.edu/about/History/digitalcomputing_2.html. "To ensure continuous operation each computer was duplexed; it actually consisted of two machines." 
  29. ↑ Redmond, Kent; Smith, Thomas (2000). From Whirlwind to Mitre: The R&D Story of The SAGE Air Defense Computer. MIT Press. pp. 187–188. ISBN 978-0262182010. 
  30. ↑ Redmond, Kent; Smith, Thomas (2000). From Whirlwind to Mitre: The R&D Story of The SAGE Air Defense Computer. MIT Press. pp. 437–438. ISBN 978-0262182010. 
  31. ↑ Ulmann, Bernd (2014). AN/FSQ-7: The Computer That Shaped The Cold War. De Gruyter Oldenbourg. pp. 70. ISBN 9783486727661. 
  32. ↑ 32.0 32.1 32.2 Cite error: Invalid <ref> tag; no text was provided for refs named SageTalk
  33. ↑ United States Navy Mathematical Computing Advisory Panel (29 June 1956). Symposium on advanced programming methods for digital computers. Washington, D.C.: Office of Naval Research, Dept. of the Navy. OCLC 10794738. 
  34. ↑ McMullen, Richard F. (1965). The Birth of SAGE, 1951–1958 (Report). ADC Hist Study 33.  (cited by Schaffel p. 207/312)
  35. ↑ "Overview |". SAGE: The First [computerized] National Air Defense Network. IBM.com. 7 March 2012. http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/sage/. "the AN/FSQ-7…was developed, built and maintained by IBM. … In June 1956, IBM delivered the prototype of the computer to be used in SAGE." 
  36. ↑ "SAGE: The New Aerial Defense System of the United States". The Military Engineer. Mar–Apr 1956.  (cited by Schaffel pp. 311, 332)
  37. ↑ 37.0 37.1 37.2 Cite error: Invalid <ref> tag; no text was provided for refs named NORAD1958A
  38. ↑ "Semi-Automatic Ground Environment (SAGE)". GlobalSecurity.org. http://www.globalsecurity.org/wmd/systems/sage.htm. 
  39. ↑ "Electronic Brain Slated To Arrive" (Google News Archive). Tri-City Herald. November 3, 1958. https://news.google.com/newspapers?id=fxsrAAAAIBAJ&pg=2577,369259&dq=mcchord+sage&hl=en. 
  40. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named IBM1959B
  41. ↑ Sokolski, Henry D (2004). Getting MAD: Nuclear Mutual Assured Destruction, Its Origins and Practice. DIANE Publishing. p. 180. ISBN 978-1-4289-1033-1. https://archive.org/details/bub_gb_9mbWB_UnEy8C. 
  42. ↑ . North American Air Defense Command. June 30, 1958.  (identified by NORAD Hist. Summary Jan–Jun '58 p. 7)Lua error: Internal error: The interpreter has terminated with signal "24".
  43. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Johnson
  44. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named NORAD1959A
  45. ↑ Theory of Programming for AN/FSQ-7 combat direction central and AN/FSQ-8 combat control central (Report). IBM Military Products Division. April 1, 1959. p. 149. http://www.bitsavers.org/pdf/ibm/sage/3-112-0_Theory_Of_Programming_Apr59.pdf. Retrieved 2012-04-02. 
  46. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named McMullen1980
  47. ↑ A Survey and Summary of Mathematical and Simulation Models as Applied to Weapon System Evaluation (Report). Aeronautical Systems Division, USAF. December 1961. http://deepblue.lib.umich.edu/bitstream/2027.42/4298/4/bab9742.0001.001.txt. Retrieved 2011-09-13. "Data from the Phase II and Phase III NORAD SAGE/ Missile Master … to validate the mathematical model [with] large-scale system tests employing SAC and ADC aircraft [under] the NORAD Joint Test Force stationed at Stewart Air Force Base."  (cites Miller 1961)
  48. ↑ "title tbd". http://www.atlasmissilesilo.com/Documents/SquadronUnitHistory/AtlasF/579thSMS/AF-D-O-579-99-RO-00009_6thBombWing_UnitHistory_1962_09_September.pdf.  pdf p. 17
  49. ↑ 49.0 49.1 Cite error: Invalid <ref> tag; no text was provided for refs named DelPapa
  50. ↑ "High Frontier : Volume 3, Number 4". Afspc.af.mil. http://www.afspc.af.mil/shared/media/document/AFD-070814-023.pdf. 
  51. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Hellige
  52. ↑ Hazlitt, Tom—Southam News Services (June 5, 1963). "The Evolution In Air Defense: NORAD Looks For A Place To Hide". The Calgary Herald. https://news.google.com/newspapers?id=rWJkAAAAIBAJ&pg=1034,838096&dq=mcchord+sage&hl=en. "The North Bay SAGE centre is the only one on the continent to be fully "hardened", or constructed underground." 
  53. ↑ "Many People, One System". Computer History Museum. http://www.computerhistory.org/revolution/networking/19/399. 
  54. ↑ Schwartz, Stephen I., ed (1998). Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940. Brookings Institution Press. p. 284. ISBN 9780815722946. https://books.google.com/books?id=8droMxkxnDwC&pg=PA284.  (the quotation is annotated with footnote 35)
  55. ↑ "SAGE Documents mapped". https://www.radomes.org/museum/sagedocs.html. 
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