Zero gyro shooting

BigWalleye · 03-07-13, 11:15 AM

Small quibble on nomenclature: In SLM-1, the Submarine Torpedo Fire Control Manual (http://www.hnsa.org/doc/attack/index.htm), what you are referring to as the "track angle", (theta sub track on your diagram) is designated the "torpedo track angle". This is distinct from the track angle, which SLM-1 defines as "The angle at the point of intercept target ships course and the submarine's course measured to port or starboard of the target ship's bow toward the submarine. Symbol: Ta." That is, track angle, as used in the WW2 USN and in many first-person accounts, is relative to the submarine's course, not the torpedo's course. Using the two interchangeably might cause confusion to someone reading first-person accounts or patrol reports.

Dorjun Driver · 03-07-13, 11:27 AM

Correct. The first diagram represents a special case where they are the same. And indeed, the second diagram is mislabeled. Thanks for the heads up.

BigWalleye · 03-07-13, 12:15 PM

The formula in your OP is correct (IMAO!), or at least agrees with my own analysis. It produces results which agree closely - but not exactly! - with the results shown on Plates XVII and XVIII in SLM-1. There are small differences, usually less than 1 degree, which I think are due to corrections for parallax and what SLM-1 calls "torpedo advance" - the distance the torpedo travels before it settles on its gyro-dictated course. It is interesting that the equation in your OP does not appear anywhere in SLM-1, and that the method used to calculate the curves of Plates XVII and XVIII is not specified either.

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03-07-13, 11:15 AM	#1
BigWalleye Sea Lord Join Date: Jul 2012 Location: On the Eye-lond, mon! Posts: 1,987 Downloads: 465 Uploads: 0	Small quibble on nomenclature: In SLM-1, the Submarine Torpedo Fire Control Manual (http://www.hnsa.org/doc/attack/index.htm), what you are referring to as the "track angle", (theta sub track on your diagram) is designated the "torpedo track angle". This is distinct from the track angle, which SLM-1 defines as "The angle at the point of intercept target ships course and the submarine's course measured to port or starboard of the target ship's bow toward the submarine. Symbol: Ta." That is, track angle, as used in the WW2 USN and in many first-person accounts, is relative to the submarine's course, not the torpedo's course. Using the two interchangeably might cause confusion to someone reading first-person accounts or patrol reports.

03-07-13, 11:27 AM	#2
Dorjun Driver Loader Join Date: Jul 2012 Location: The Upper Left Edge Posts: 81 Downloads: 77 Uploads: 0	Correct. The first diagram represents a special case where they are the same. And indeed, the second diagram is mislabeled. Thanks for the heads up.

03-07-13, 12:15 PM	#3
BigWalleye Sea Lord Join Date: Jul 2012 Location: On the Eye-lond, mon! Posts: 1,987 Downloads: 465 Uploads: 0	The formula in your OP is correct (IMAO!), or at least agrees with my own analysis. It produces results which agree closely - but not exactly! - with the results shown on Plates XVII and XVIII in SLM-1. There are small differences, usually less than 1 degree, which I think are due to corrections for parallax and what SLM-1 calls "torpedo advance" - the distance the torpedo travels before it settles on its gyro-dictated course. It is interesting that the equation in your OP does not appear anywhere in SLM-1, and that the method used to calculate the curves of Plates XVII and XVIII is not specified either.