Editing Semi-Automatic Ground Environment (section)

===Valley Committee===
[[File:Museum of Science, Boston, MA - IMG 3168.JPG|thumb|right|Whirlwind computer elements: [[Magnetic-core memory|core memory]] (left) and operator console]]
[[File:Module from a SAGE computer.jpg|right|thumb|Module from a SAGE]]
[[File:RCA 6499 Radechon tube.jpg|right|thumb|The RCA #6499 Radechon tube was used for [[random-access memory]] in the computers.]]

When the [[Soviet Union]] tested [[RDS-1|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".<ref name=valley>
{{cite web
 | title= The Valley Committee
 | website= Lincoln Laboratory
 | date= 1995
 | url= https://www.ll.mit.edu/about/History/origins.html
 | url-status= live
 | archive-url= https://web.archive.org/web/20160401230140/http://www.ll.mit.edu/about/History/origins.html
 | archive-date= 2016-04-01
}}
</ref>

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.<ref name=valley/>

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.<ref name=valley/> 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.<ref name="Quarterly Progress Report">
{{Cite report
 | title= Quarterly Progress Report
 | date= June 1952
 | publisher= Lincoln Laboratories
}}
 (cited by Schaffel p. 197)
</ref><ref name="web.mit.edu">
{{Cite news
 | title= Physicist George Valley Jr. is dead at 86
 | date= October 20, 1999
 | newspaper= [[MIT Tech Talk]]
 | format= MITnews webpage
 | url= http://web.mit.edu/newsoffice/1999/valley-1020.html
 | access-date= 2012-07-15
 | url-status= live
 | archive-url= https://web.archive.org/web/20121018210958/http://web.mit.edu/newsoffice/1999/valley-1020.html
 | archive-date= October 18, 2012
}}
</ref>

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]]<ref>{{cite web| url = https://www.computer.org/csdl/proceedings-article/afips/1951/50400070/12OmNBvkdmJ| title = 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}}</ref> as a general purpose [[flight simulator]] that could simulate any current or future aircraft by changing its software.<ref name=valley/>

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.<ref name=valley/>