TDC and realistic playing - Page 3

Daniel Prates · 12-05-11, 07:57 AM

Quote:

Originally Posted by Rockin Robbins

First of all, the Germans did not have a high rate of success. They just had a lot of U-Boats out there, most of which never sank a single target. Only 10 percent of them had the lion's share of the tonnage sunk. The statistics on the number of U-Boats sunk having never fired a torpedo in action is just astounding.

What success they had was due to their numbers and the lack of any coordinated anti-submarine tactics early in the war. Once the British perfected how destroyers and planes were to be handled, the sub war was just about over. Then Admiral Daniel Gallery came on the scene with his jeep carrier hunter-killer groups and the nails were all in the coffins. Predictably, the U-Boats were unable to be a decisive influence on the war, aside from the colossal waste of men and resources the Germans flushed down the drain to use a weapon unable to help their cause.

For better or worse, the Germans were entirely dependent on their land-based warfare for any success they were going to have. Anything (read Navy) that subtracted from their land based assets hurt their war effort. The U-Boats did worse than that, sucking the US into the war and guaranteeing complete German defeat.

Once the American boats had radar, THEN deducing AoB from radar plot was more accurate than visual estimate and they used that number. With visual targeting, the AoB estimate was the MOST reliable number they had. When you are analyzing, you always deduce more doubtful numbers based on your most reliable ones. That is what many of the targeting gurus on Subsim have forgotten and why their methods were not used during the war.

These guys in the war were as smart as we are. There's nothing we've thought of that they didn't. If they didn't time ship length by the wire to obtain speed, and they did not, there is a good reason. That is that target identification and actual target lengths were among the least reliable of their information. It would have been foolishness to try to calculate anything based on defective data. So they didn't.

Well then, I stand corrected...

I wasn't thinking about objective data, actually, as indeed the sub vs ship score does not compare to a basketball game - obviously. In that sense, yeah, not successful. I was refering to the fact that u-boats were perceived as a serious threath, dragged a lot of resources to counter them, and is mentioned in some moments as being near to turn comercial shipping inviable, during the first half of the war.

All that without radar. I recall this thread being about radar being indispensable for a minimally-usefull submarine, a thing that the german experience shows otherwise. That's all.

commandosolo2009 · 12-05-11, 03:03 PM

Quote:

Originally Posted by Radio

Atm I am playing the game (with my own megamod-soup) on nthe hardest settings, meaning no mapupdate, no targeting assistents etc. and I realized one thing:

The TDC is rather useless! The way one usually plays (with autopdate etc) the game gives you way too precise target data, however if you are using your own position marks and try to find the data yourself the TDC becomes virtually useless.

Why?

-During the day you will not be able to use the periscope w/o being detected.
-During the night you will not see the target good enough to get useful data
-If the weather is good your periscope is easier to see
-If the weather is bad it will ruin your target gathering procedures

This changed my way of getting target data and attacking completely.
The radar becomes the sensor of choice, followed by the active sonar, the later being restricted to targets w/o hydrophones, meaning that every warship and most late-war merchants can hear you etc.

It also slows down the attack speed, whereas you can normally (with map-updates) can use the 3 minute-rule to get target speed and course I now use a 30 minute rule with the radar.

It basically boils down to RockinRobbins/Dick O#Kane methods with some guestimating and more manoeuvering during th final attack phase.

I can simply not see a way to use the TDC here in a practical manner.

What are your observations, do you have better ideas for the TDC "problem"? Or do you agree to my observation?

The TDC is just a prediction device people. Its not designed to be the attack method of choice. It just provides an old era target point estimation provided the target doesnt detect you, which means, you havent been spotted.

Further, if you complain of a damaged TDC, you should know that experienced sailors eyes IRL, were the most accurate. As a proof, the submariner doesnt follow the TDC, the TDC follows his input. And at some point in time, if the target happens to be where its supposed to be, then the TDC did its job, and the data collection was flawless. But that wasnt the issue in the great war. It was the defective torpedoes that BuOrd issued to the navy, that at some point, one guy looking at an abacus counting sunk ships over a period of time, were too few for the torpedoes issued. And this instigated an inquiry by Lockwood, who discovered the defects and ordered contact pistol by defualt for the remainder of the war.

Maybe you know the info above, maybe you dont. But my point is, TDC is a checking device, not a targeting device. I doubt in harbor raids that they even turned it on... Not this clownish stuff we do in a sim..

Arlo · 12-05-11, 03:45 PM

http://en.wikipedia.org/wiki/Target_Data_Computer

The TDC was designed to provide fire-control solutions for submarine torpedo launches against ships running on the surface (surface warships used a different computer for their torpedo launches).[4] The TDC had a wide array of handcranks, dials and switches for data input and display.[5] 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,[6] radar, and sonar)
torpedo type and speed (type was needed to deal with the different torpedo ballistics)

The TDC performed the trigonometric calculations required to compute a target intercept course for the torpedo. It also had an electromechanical interface to the torpedoes that allowed it to automatically set the torpedo courses while they were in their tubes, ready to be launched.
The TDC's target tracking capability was used by the fire control party to continuously update the fire control solution to the torpedoes even while the submarine was maneuvering. The TDC's target tracking ability also allowed the submarine to accurately launch torpedoes even when the target was temporarily obscured by smoke or fog.

TDC functional description

Since the TDC actually performed two separate functions, generating target position estimates and computing torpedo firing angles, the TDC actually consisted of two types of analog computers:

Angle solver: This computer calculates the required gyro angle. The TDC had separate angle solvers for the forward and aft torpedo tubes.
Position keeper: This computer generates a continuously updated estimate of the target position based on earlier target position measurements.[35]

[edit] Angle solver

The equations implemented in the angle solver can be found in the Torpedo Data Computer manual.[36] The Submarine Torpedo Fire Control Manual[37] discusses the calculations in a general sense and a greatly abbreviated form of that discussion is presented here.

The general torpedo fire control problem is illustrated in Figure 2. The problem is made more tractable if we assume:

The periscope is on the line formed by the torpedo running along its course
The target moves on a fixed course and speed
The torpedo moves on a fixed course and speed

Figure 3: The Torpedo Fire Control Triangle

As can be seen in Figure 2, these assumptions are not true in general because of the torpedo ballistic characteristics and torpedo tube parallax. Providing the details as to how to correct the torpedo gyro angle calculation for ballistics and parallax is complicated and beyond the scope of this article. Most discussions of gyro angle determination take the simpler approach of using Figure 3, which is called the torpedo fire control triangle.[7][8] Figure 3 provides an accurate model for computing the gyro angle when the gyro angle is small, usually less than < 30o.[38]
The effects of parallax and ballistics are minimal for small gyro angle launches because the course deviations they cause are usually small enough to be ignorable. U.S. submarines during World War II preferred to fire their torpedoes at small gyro angles because the TDC's fire control solutions were most accurate for small angles.[39]
The problem of computing the gyro angle setting is a trigonometry problem that is simplified by first considering the calculation of the deflection angle, which ignores torpedo ballistics and parallax.[40] For small gyro angles, ***952;Gyro ***8776; ***952;Bearing - ***952;Deflection. A direct application of the law of sines to Figure 3 produces Equation 1.
(Equation 1)

where
vTarget is the velocity of the target.vTorpedo is the velocity of the torpedo.***952;Bow is the angle of the target ship bow relative to the periscope line of sight.***952;Deflection is the angle of the torpedo course relative to the periscope line of sight.Range plays no role in Equation 1, which is true as long as the three assumptions are met. In fact, Equation 1 is the same equation solved by the mechanical sights of steerable torpedo tubes used on surface ships during World War I and World War II. Torpedo launches from steerable torpedo tubes meet the three stated assumptions well. However, an accurate torpedo launch from a submarine requires parallax and torpedo ballistic corrections when gyro angles are large. These corrections require knowing range accurately. When the target range was not known, torpedo launches requiring large gyro angles were not recommended.[41]
Equation 1 is frequently modified to substitute track angle for deflection angle (track angle is defined in Figure 2, ***952;Track=***952;Bow+***952;Deflection). This modification is illustrated with Equation 2.
(Equation 2)

where
***952;Track is the angle between the target ship's course and the torpedo's course.

Figure 4: Deflection Angle Versus Track Angle and Target Speed (***952;Gyro = 0o).

A number of publications[42][43] state the optimum torpedo track angle as 110o for a Mk 14 (46 knot weapon). Figure 4 shows a plot of the deflection angle versus track angle when the gyro angle is 0o (i.e., ***952;Deflection=***952;Bearing).[44] Optimum track angle is defined as the point of minimum deflection angle sensitivity to track angle errors for a given target speed. This minimum occurs at the points of zero slope on the curves in Figure 4 (these points are marked by small triangles).
The curves show the solutions of Equation 2 for deflection angle as a function of target speed and track angle. Figure 4 confirms that 110o is the optimum track angle for a 16-knot (30 km/h) target, which would be a common ship speed.[45]
There is fairly complete documentation available for a Japanese torpedo fire control computer that goes through the details of correcting for the ballistic and parallax factors. While the TDC may not have used exactly the same approach, it was likely very similar.
[edit] Position keeper

As with the angle solver the equations implemented in the angle solver can found in the Torpedo Data Computer manual.[36] Similar functions were implemented in the rangekeepers for surface ship-based fire control systems. For a general discussion of the principles behind the position keeper, see Rangekeeper.

Muty · 12-13-11, 10:18 AM

Hey guys thanks for the outstanding info you posted here. You answered some of the questions that were bothering me for years.

berobispo · 12-15-11, 08:12 AM

I have become a big fan of the position keeper since I installed the Optical targeting correction mod (OTC). It has a 1-degree bearing periscope/TBT, this way you can compare generated bearing with observed ones very well. Even if your solution still lags 1 degree every 2 minutes for example and you aim for a torpedo run of 2 minutes, simply set a 1 degree forward angle in the torpedo settings.

For spreads I use Hitman's ingame torpedo spread angle calculator.

There still is the bug with the AoB updating/not updating when a new range is sent, but I have built a wiz-wheel to know exactly which AoB to enter for any observed bearing and assumed enemy course. My best shot so far was a MOT (from a spread of two, the MOT actually went underneath because of faulty depth setting, one missed) on a transiting DD going 12kts with a MK14 torpedo run of 6:30 minutes (slow speed setting).

Daniel Prates · 12-17-11, 08:31 AM

Quote:

Originally Posted by berobispo

I have become a big fan of the position keeper since I installed the Optical targeting correction mod (OTC).

It is great, isnt't it?

12-05-11, 03:45 PM	#33
Arlo The Old Man Join Date: Nov 2003 Posts: 1,304 Downloads: 214 Uploads: 0	http://en.wikipedia.org/wiki/Target_Data_Computer The TDC was designed to provide fire-control solutions for submarine torpedo launches against ships running on the surface (surface warships used a different computer for their torpedo launches).[4] The TDC had a wide array of handcranks, dials and switches for data input and display.[5] 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,[6] radar, and sonar) torpedo type and speed (type was needed to deal with the different torpedo ballistics) The TDC performed the trigonometric calculations required to compute a target intercept course for the torpedo. It also had an electromechanical interface to the torpedoes that allowed it to automatically set the torpedo courses while they were in their tubes, ready to be launched. The TDC's target tracking capability was used by the fire control party to continuously update the fire control solution to the torpedoes even while the submarine was maneuvering. The TDC's target tracking ability also allowed the submarine to accurately launch torpedoes even when the target was temporarily obscured by smoke or fog. TDC functional description Since the TDC actually performed two separate functions, generating target position estimates and computing torpedo firing angles, the TDC actually consisted of two types of analog computers: Angle solver: This computer calculates the required gyro angle. The TDC had separate angle solvers for the forward and aft torpedo tubes. Position keeper: This computer generates a continuously updated estimate of the target position based on earlier target position measurements.[35] [edit] Angle solver The equations implemented in the angle solver can be found in the Torpedo Data Computer manual.[36] The Submarine Torpedo Fire Control Manual[37] discusses the calculations in a general sense and a greatly abbreviated form of that discussion is presented here. The general torpedo fire control problem is illustrated in Figure 2. The problem is made more tractable if we assume: The periscope is on the line formed by the torpedo running along its course The target moves on a fixed course and speed The torpedo moves on a fixed course and speed Figure 3: The Torpedo Fire Control Triangle As can be seen in Figure 2, these assumptions are not true in general because of the torpedo ballistic characteristics and torpedo tube parallax. Providing the details as to how to correct the torpedo gyro angle calculation for ballistics and parallax is complicated and beyond the scope of this article. Most discussions of gyro angle determination take the simpler approach of using Figure 3, which is called the torpedo fire control triangle.[7][8] Figure 3 provides an accurate model for computing the gyro angle when the gyro angle is small, usually less than < 30o.[38] The effects of parallax and ballistics are minimal for small gyro angle launches because the course deviations they cause are usually small enough to be ignorable. U.S. submarines during World War II preferred to fire their torpedoes at small gyro angles because the TDC's fire control solutions were most accurate for small angles.[39] The problem of computing the gyro angle setting is a trigonometry problem that is simplified by first considering the calculation of the deflection angle, which ignores torpedo ballistics and parallax.[40] For small gyro angles, *952;Gyro 8776; 952;Bearing - 952;Deflection. A direct application of the law of sines to Figure 3 produces Equation 1. (Equation 1) where vTarget* is the velocity of the target.vTorpedo is the velocity of the torpedo.*952;Bow is the angle of the target ship bow relative to the periscope line of sight.952;Deflection is the angle of the torpedo course relative to the periscope line of sight.Range plays no role in Equation 1, which is true as long as the three assumptions are met. In fact, Equation 1 is the same equation solved by the mechanical sights of steerable torpedo tubes used on surface ships during World War I and World War II. Torpedo launches from steerable torpedo tubes meet the three stated assumptions well. However, an accurate torpedo launch from a submarine requires parallax and torpedo ballistic corrections when gyro angles are large. These corrections require knowing range accurately. When the target range was not known, torpedo launches requiring large gyro angles were not recommended.[41] Equation 1 is frequently modified to substitute track angle for deflection angle (track angle is defined in Figure 2, 952;Track=952;Bow+952;Deflection). This modification is illustrated with Equation 2. (Equation 2) where 952;Track is the angle between the target ship's course and the torpedo's course. Figure 4: Deflection Angle Versus Track Angle and Target Speed (*952;Gyro = 0o). A number of publications[42][43] state the optimum torpedo track angle as 110o for a Mk 14 (46 knot weapon). Figure 4 shows a plot of the deflection angle versus track angle when the gyro angle is 0o (i.e., 952;Deflection=952;Bearing).[44] Optimum track angle is defined as the point of minimum deflection angle sensitivity to track angle errors for a given target speed. This minimum occurs at the points of zero slope on the curves in Figure 4 (these points are marked by small triangles). The curves show the solutions of Equation 2 for deflection angle as a function of target speed and track angle. Figure 4 confirms that 110o is the optimum track angle for a 16-knot (30 km/h) target, which would be a common ship speed.[45] There is fairly complete documentation available for a Japanese torpedo fire control computer that goes through the details of correcting for the ballistic and parallax factors. While the TDC may not have used exactly the same approach, it was likely very similar. [edit] Position keeper* As with the angle solver the equations implemented in the angle solver can found in the Torpedo Data Computer manual.[36] Similar functions were implemented in the rangekeepers for surface ship-based fire control systems. For a general discussion of the principles behind the position keeper, see Rangekeeper. __________________ -Arlo

12-13-11, 10:18 AM	#34
Muty Nub Join Date: Mar 2011 Posts: 3 Downloads: 18 Uploads: 0	Hey guys thanks for the outstanding info you posted here. You answered some of the questions that were bothering me for years.

12-15-11, 08:12 AM	#35
berobispo Helmsman Join Date: May 2009 Location: Germany Posts: 102 Downloads: 174 Uploads: 4	I have become a big fan of the position keeper since I installed the Optical targeting correction mod (OTC). It has a 1-degree bearing periscope/TBT, this way you can compare generated bearing with observed ones very well. Even if your solution still lags 1 degree every 2 minutes for example and you aim for a torpedo run of 2 minutes, simply set a 1 degree forward angle in the torpedo settings. For spreads I use Hitman's ingame torpedo spread angle calculator. There still is the bug with the AoB updating/not updating when a new range is sent, but I have built a wiz-wheel to know exactly which AoB to enter for any observed bearing and assumed enemy course. My best shot so far was a MOT (from a spread of two, the MOT actually went underneath because of faulty depth setting, one missed) on a transiting DD going 12kts with a MK14 torpedo run of 6:30 minutes (slow speed setting).