Torpedo Data Computer: Difference between revisions

Revision as of 18:14, 18 January 2023

Revision as of 18:16, 18 January 2023

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Straight running torpedoes were usually launched in salvo (i.e. multiple launches in a short period of time)<ref name="spread">{{harvnb|COMSUBATL|1950|loc=§ Definitions pp 1–9}}</ref> or a spread (i.e. multiple launches with slight angle offsets)<ref name="spread"/> to increase the probability of striking the target given the inaccuracies present in the measurement of angles, target range, target speed, torpedo track angle, and torpedo speed.

Salvos and spreads were also launched to strike tough targets multiple times to ensure their destruction.<ref name = doctrine>{{cite book | title = Current Submarine Doctrine | editor = Commander Submarine Force, Pacific Fleet | orig-year = 1944-02 | date = 2006-02-17 | pages = paragraph 4614 | chapter = Attacks -- General (Chapter IV, Section 1) | chapter-url = http://www.history.navy.mil/library/online/ss-doc-4.htm | url = http://www.history.navy.mil/library/online/sub_doctrine.htm | access-date = 2006-07-02 }}</ref> The TDC supported the firing of torpedo salvos by allowing short time offsets between firings and torpedo spreads by adding small angle offsets to each torpedo's gyro angle. Before the [[ROKS Cheonan sinking|sinking]] of [[South Korea]]'s [[{{ship|ROKS |Cheonan (|PCC-772)|ROKS ''Cheonan'']]6}} by [[North Korea]] in 2010, the last warship sunk by a submarine torpedo attack, the [[ARA General Belgrano|ARA ''General Belgrano'']] in 1982, was struck by two torpedoes from a three torpedo spread.<ref name=belgrano_attack>{{citation| url=http://www.geocities.com/nmdecke/Submarines.html| title = Submarines 1950-2000, a study in unused potential| access-date = 2006-08-20| author = Nathan Decker | date = July 2005|archive-url=https://web.archive.org/web/20070317172208/http://www.geocities.com/nmdecke/Submarines.html|archive-date=2007-03-17}}</ref>

[[Image:Torpedo Data Computer, interior.jpg|thumb|right|A look inside the TDC showing the motors driving the Position Keeper. <!-- Ref: http://www.maritime.org/doc/tdc/pg105.htm -->]]

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*comparing the predicted position against the actual position and correcting the estimated parameters as required to achieve agreement between the predictions and observation. Agreement between prediction and observation means that the target course, speed, and range estimates are accurate.

Estimating the target's course was generally considered the most difficult of the observation tasks. The accuracy of the result was highly dependent on the experience of the skipper. During combat, the actual course of the target was not usually determined but instead the skippers determined a related quantity called "[[angle on the bow]]." Angle on the bow is the angle formed by the target course and the line of sight to the submarine. Some skippers, like [[Dick O'Kane|Richard O'Kane]], practiced determining the angle on the bow by looking at [[Imperial Japanese Navy|IJN]] ship models mounted on a calibrated [[lazy Susan]] through an inverted binocular barrel.<ref name="Okane">{{cite book | last = O'Kane | first = Richard H. | title = Wahoo: The Patrols of America's Most Famous World War II Submarine | orig-year = 1987 | edition = Bantam | year = 1989 | publisher = Bantam | ___location = New York | isbn= 0-553-28161-5 | pages = 108–109 | chapter = Part 4: Chapter 1 }}</ref>

To generate target position data versus time, the TDC needed to solve the equations of motion for the target relative to the submarine. The equations of motion are differential equations and the TDC used mechanical integrators to generate its solution.<ref name=CBC>{{cite web | last = Bromley | first = Allan | title = Analog Computing Devices | work = Computing Before Computers | year = 1990 | url = http://ed-thelen.org/comp-hist/CBC.html | access-date = 2006-07-22 }}</ref>