Torpedo data computer

[Nikdunaev]

Hello!

I just recently came back to playing the Silent Hunter series after a pretty long break and thought I need to refresh my knowledge of the subject a bit.

Then I found this thread http://www.subsim.com/radioroom/showthread.php?t=221540

After reading through some of the historical documents that are linked in the first post I noticed one thing. The Submarine Torpedo Fire Control Manual refers to the torpedo data computer as Mark 4 TDC. At the same time the computer manual from the same thread is for the Mark 3.
So I am wondering what is the difference between the Mark 3 and the Mark 4 TDC? Which one do we have modeled in the game?
I was only able to find out that four was introduced later in the war and had an additional block called the receiver. But pretty much no information on what it does and what changes in operation of the instrument.

Also as I understand there should be a manual for Mark 4 similar to that for Mark 3 that we have and also another paper on each of them describing the operation rather their internal workings. Does anyone have a copy of any of those or know where it can be found? I am sure many subsimmers would love to read them.

Any help appreciated!

[Aktungbby]

Nikdunaev!:Kaleun_Salute: after a long silent run!

[THEBERBSTER]

A Warm Welcome Back To The Subsim Community > Nikdunaev
Subsim <> Make A Donation <> See The Benefits <> Support The Community (http://www.subsim.com/radioroom/showpost.php?p=2027002&postcount=1)
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[aanker]

Hello!

I just recently came back to playing the Silent Hunter series after a pretty long break and thought I need to refresh my knowledge of the subject a bit.

Then I found this thread http://www.subsim.com/radioroom/showthread.php?t=221540

After reading through some of the historical documents that are linked in the first post I noticed one thing. The Submarine Torpedo Fire Control Manual refers to the torpedo data computer as Mark 4 TDC. At the same time the computer manual from the same thread is for the Mark 3.
So I am wondering what is the difference between the Mark 3 and the Mark 4 TDC? Which one do we have modeled in the game?
I was only able to find out that four was introduced later in the war and had an additional block called the receiver. But pretty much no information on what it does and what changes in operation of the instrument.

Also as I understand there should be a manual for Mark 4 similar to that for Mark 3 that we have and also another paper on each of them describing the operation rather their internal workings. Does anyone have a copy of any of those or know where it can be found? I am sure many subsimmers would love to read them.

Any help appreciated!
Rockin Robbins has a pretty extensive list there - right out of my bookmarks too, I don't know how he did that...

Search here:
http://www.hnsa.org/

Mark 3 - yeah you want Mark 4
https://maritime.org/doc/tdc/index.htm

Submarine Torpedo Fire Control Manual
https://maritime.org/doc/attack/index.htm

More links
http://www.subsim.com/radioroom//showpost.php?p=1383465&postcount=23

- and these guys have a nice list:
https://forums.ubi.com/showthread.php/230064-WWII-era-submarine-manuals-and-documents-Forums

You may need to go to the National Archives...

Happy Hunting!

[Nikdunaev]

Rockin Robbins has a pretty extensive list there - right out of my bookmarks too, I don't know how he did that...

Search here:
http://www.hnsa.org/

Mark 3 - yeah you want Mark 4
https://maritime.org/doc/tdc/index.htm

Submarine Torpedo Fire Control Manual
https://maritime.org/doc/attack/index.htm

More links
http://www.subsim.com/radioroom//showpost.php?p=1383465&postcount=23

- and these guys have a nice list:
https://forums.ubi.com/showthread.php/230064-WWII-era-submarine-manuals-and-documents-Forums

You may need to go to the National Archives...

Happy Hunting!

Thank you but still nothing seems to be related in particular to the Mark 4 TDC. Its description does not seem to be easily findable on the web for some reason even though there is a lot on Mark 3.
Also I thought I made it clear that I came up with that question after already reading both the Submarine Torpedo Fire Control Manual and the Torpedo Computer Manual for the Mark 3. In fact it was reading these two that made me wonder what the difference between the Mark 3 and Mark 4 is.

[Aktungbby]

Thank you but still nothing seems to be related in particular to the Mark 4 TDC.
Also I thought I made it clear that I came up with that question after already reading both the Submarine Torpedo Fire Control Manual and the Torpedo Computer Manual for the Mark 3. In fact it was reading these two that made me wonder what the difference between the Mark 3 and Mark 4 is http://www.usscod.org/tdc.html (http://www.usscod.org/tdc.html) The TDC was unique in World War II. It was the computational part of the first submerged integrated fire control system that could track a target and continuously aim torpedoes by setting their gyro angles. The TDC Mark III https://upload.wikimedia.org/wikipedia/commons/0/0a/TDCfullview.jpg<USS Pampanito gave the U.S. fleet submarine the ability to fire torpedoes without first estimating a future firing position, changing the ship's course, or steering to that position....Instead of hoping that nothing in the setup changed, a fleet submarine with the TDC could fire at the target when the captain judged the probability of making hits to be optimal.:down: (http://www.usscod.org/tdc.html) The Mark III computer consisted of two sections, the position keeper and the angle solver. The Mark IV TDC now on USS COD also includes a center section called the receiver.> http://www.usscod.org/graphics/tdc2.jpg THIS ALLOWED FOR CONSTANT POSITION UPGRADES The position keeper solves the equations of motion integrated over time. The result is a continuous prediction of where the target is at any instant. Successive measurements of the targets' position are compared to the position keeper predictions and corrections for error are introduced with the hand cranks. The predicted target position becomes more accurate as more measurements make the corrections smaller.:yeah: It is typical to get an accurate track on the target after about three or four observations under good conditions. The U.S. Navy thus had a system that would point the torpedoes at a target as the fire control problem developed. The TDC Mark IV was the only torpedo targeting system of the time that both solved for the gyro angle and tracked the target in real time. The comparable systems used by both Germany and Japan could compute and set the gyro angle for a fixed time in the future, but did not track the target. Thus the idea of the position keeper, and its reiterative reduction of target position error was unique to the U.S.
hope this helps!:subsim: :salute: http://usscod.org/tdc_schematic.jpg

[Nikdunaev]

http://www.usscod.org/tdc.html (http://www.usscod.org/tdc.html) :subsim: :salute:

So the difference between the versions indeed seems to be the addition of the third block called the receiver. What does that receiver do though? The name and your diagram suggest it receives some extra data from some external stations or something like that... But what kind of data exactly? Is it related to automatically entering the stuff sent by the radar and sonar operators and continuously following the periscope without a human operator matching the bearing all the time?

I mean I am clear about the functions of the position keeper and the angle solver blocks but not about those new extra features of the Mark IV.

Also I have just read that the new computer is related to the introduction of Mark 18 torpedo. If so then does that mean that the Mark 3 computer could not be used with them?

[aanker]

USS COD has the only working Mark 4. I don't know where Terry is but the COD folks should know.

They might be a good source too.

As I said, the National Archives

Here is the COD web version
http://www.usscod.org/tdc.html
and
http://www.usscod.org/tdc-restore.html

[propbeanie]

Aktungbby has a quote there: "THIS ALLOWED FOR CONSTANT POSITION UPGRADES The position keeper solves the equations of motion integrated over time. The result is a continuous prediction of where the target is at any instant. Successive measurements of the targets' position are compared to the position keeper predictions and corrections for error are introduced with the hand cranks. The predicted target position becomes more accurate as more measurements make the corrections smaller. It is typical to get an accurate track on the target after about three or four observations under good conditions."

... and the diagram shows the inputs on the left and near the top for several "real-time" data updates that flow through the "Receiver" section, with multiple choices for data flow and inputs, whether periscope, hydrophone, whatever, along with updates of the subs own course and speed - looks to me, anyway. It also looks like any "adjustments" made with the hand cranks at the receiver fed back to the "measuring device" stations. The Mark 18 is a copy of a German electric torpedo found onshore US in 1942 (although the US had been working on one already, and the Mark 4 came out in 1943... one of my "searches" brought up a revovly link, which is nothing more than the wikipedia.org article on the mark 18, and it showed "The Mark 4 was developed to support the Mark 18 torpedo...", but I could not find that in the text itself (old eyes??)...

If you're anywhere near Washington state (Keyport), it might worth the while to visit
http://www.navalunderseamuseum.org/permanent/

They say they have a Mark 4 there in the Silent Victory exhibit.

[Nikdunaev]

Sadly enough all those places are really too far away from me to visit in person.
I am on the other side of the Atlantic :)

But I think I get the overall idea...

What is interesting though is why is there so little material on the Mark IV out there? Given that it was logically considered an improvement over the old version and was installed on the new boats including those built some time after the war and also probably over time retrofitted to the older ones...
Should it not be more common today in both the surviving boats and the documents than the Mark III?

Anyway if there is any chance to get a scan or just the text or any digital version of the OP1442/1442A/1056A pamphlets... That would be absolutely amazing!

[aanker]

Maybe try explaining your interest in an email to USS COD. There is a webmaster link and I'm pretty sure they could forward you to the right people.

I've found that these types of sites - real WWII submarine restoration & basically museum sites are more than happy to share what they know to serious people such as yourself.

It's worth a try and the worst that can happen is they say, 'no' - but I don't think they will do that.

Don't give up!