Torpedo Data Computer: Difference between revisions

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[[Image:TDCfullview.jpg|thumb|right|U.S. Navy Mk III Torpedo Data Computer, the standard US Navy torpedo fire control computer during World War II. Later in World War II (1943), the TDC Mk III was replaced by the TDC Mk IV, which was an improved and larger version of the Mk III.]]

The '''Torpedo Data Computer''' ('''TDC''') was an early [[electromechanical]] [[analog computer]] used for [[torpedo]] [[fire-control system|fire-control]] on [[US Navy|American]] [[submarine]]s during [[World War II]]. [[Royal Navy#1914–1945|Britain]], [[Kriegsmarine|Germany]], and [[Imperial Japanese Navy|Japan]] also developed automated torpedo fire control equipment, but none were as advanced as the [[US Navy]]'s TDC,<ref name=JapanGermany>{{cite book | last = Friedman | first = Norman | title = US Submarines Through 1945: An Illustrated Design History | year = 1995 | publisher = Naval Institute Press | isbn=1-55750-263-3 | pages = 195 |ref=harv}}</ref> as it was able to automatically track the target rather than simply offering an instantaneous firing solution. This unique capability of the TDC set the standard for submarine torpedo [[Fire-control system|fire control]] during World War II.<ref name=computermuseum>{{cite web | title = Analog Computers | work = Lexikon's History of Computing | year = 1995 | url = http://www.computermuseum.li/Testpage/AnalogComputers.htm#Restoration | accessdate = 2006-07-03 | deadurlurl-status = yesdead | archiveurl = https://www.webcitation.org/69LF1Sr40?url=http://www.computermuseum.li/Testpage/AnalogComputers.htm#Restoration | archivedate = 2012-07-22 | df = }}

</ref><ref name=OtherTrackers>While the TDC's target tracking abilities were unique for submarine torpedo fire control during WWII, target tracking was used on surface ship torpedo fire control systems by a number of nations (see references in this article to [http://www.maritime.org/doc/destroyer/ddfc/index.htm US destroyer] and [http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ%20Reports/USNTMJ-200F-0086-0124%20Report%20O-32.pdf Japanese torpedo fire control] {{Webarchive|url=https://web.archive.org/web/20070720142332/http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ%20Reports/USNTMJ-200F-0086-0124%20Report%20O-32.pdf |date=2007-07-20 }}). The TDC was the first analog computer to miniaturize the capability enough for deployment on a submarine.</ref>

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|accessdate=2006-07-11}}</ref> These were often "woefully inaccurate",<ref>Holwitt, p. 147.</ref> which helps explain why torpedo spreads were advised.

During World War II, Germany,<ref>{{cite web |url=http://www.msichicago.org/exhibit/U505/virtualtour/photo_tour/contower.html |title=Archived copy |accessdate=2006-08-01 |deadurlurl-status=yesdead |archiveurl=https://archive.is/20050608024538/http://www.msichicago.org/exhibit/U505/virtualtour/photo_tour/contower.html |archivedate=2005-06-08 |df= }}</ref> Japan,<ref>[http://web.ukonline.co.uk/chalcraft/sm/attack.html Britain] {{Webarchive|url=https://web.archive.org/web/20060619061752/http://web.ukonline.co.uk/chalcraft/sm/attack.html |date=2006-06-19 }}</ref> and the United States each developed [[analog computer]]s to automate the process of computing the required torpedo course.<ref name=JapanTechnology>{{cite book | last = Jackson, USNR | first = Lt.(jg) J.G. | url = http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ%20Reports/USNTMJ-200F-0086-0124%20Report%20O-32.pdf | title = Japanese Torpedo Fire Control | date = February 1946 | publisher = US Naval Technical Mission to Japan | id = Fascicle O-1, Target O-32 | format = PDF | deadurlurl-status = yesdead | archiveurl = https://web.archive.org/web/20070720142332/http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ%20Reports/USNTMJ-200F-0086-0124%20Report%20O-32.pdf | archivedate = 2007-07-20 | df = }}</ref>

In 1932, the [[Bureau of Ordnance]] (BuOrd) initiated development of the TDC with [[Arma Corporation]] and [[Ford Instruments]].<ref name="Holwitt, p.147">Holwitt, p.147.</ref> This culminated in the "very complicated" Mark 1 in 1938.<ref name="Holwitt, p.147"/> This was retrofitted into older boats, beginning with [[USS Dolphin (SS-169)|''Dolphin'']] and up through the newest [[Salmon class submarine|''Salmon'']]s.<ref name="Holwitt, p.147"/>

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The packaging problem was severe and the performance of some early torpedo fire control equipment was hampered by the need to make it small.<ref name=USSubHis>{{harvnb|Friedman|1995|p=350}}</ref> It had an array of handcranks, dials, and switches for data input and display.<ref>http://www.fleetsubmarine.com/tdc.html</ref> To generate a fire control solution, it required inputs on

*submarine course and speed, which were read automatically from the submarine's [[gyrocompass]] and [[pitometer log]]

*estimated target course, speed, and range information (obtained using data from the submarine's [[periscope]], [[Target Bearing Transmitter]] (TBT),<ref>{{cite web |url=http://www.bowfin.org/website/bowfin/bowfin_systems/TBT/tbt.htm |title=Archived copy |accessdate=2006-07-28 |deadurlurl-status=yesdead |archiveurl=https://web.archive.org/web/20060720074815/http://www.bowfin.org/website/bowfin/bowfin_systems/TBT/tbt.htm |archivedate=2006-07-20 |df= }}</ref> [[radar]], and [[sonar]])

*torpedo type and speed (type was needed to deal with the different torpedo ballistics)<!--This was accounted for by changing cams in the machine, but can't recall if the source is Blair, Grider, O'Kane, or Beach...or somewhere else...-->