Two Historical Firing Methods: Ausdampfverfahren and Auswanderungsverfahren

[derstosstrupp]

Hi All,
Introducing two firing/data acquisition methods which, after repeated tests using the torpedo tutorial in the academy, have proven to be successful and are 100% historically accurate, which ought to make other fellow “targeting realism” die-hards grin. I am using NYGM with Hitman’s GUI.
These methods are:

1. Ausdampfverfahren - (constant bearing to target)
a. Advantages/Requirements:
i. requires no estimate of target AOB or speed prior to firing
ii. requires only maintaining a constant bearing (collision course) and knowledge of own speed
iii. requires range estimate to correct for parallax prior to shot, but can be roughly estimated
iv. can use to derive target speed with solid knowledge of AOB
b. Disadvantages:
i. not optimal when target AOB is small when on collision course due to small target presented for the torpedo
ii. less accurate than plotting during the overhaul maneuver, and is thus best used when encountering the target forward of the beam (say at 45 deg AOB or so)
iii. should not be used for night surface attacks, as Hundekurve (dog’s course, keeping bow to target) should be followed to minimize sub silhouette.

2. Auswanderungsverfahren - (change in bearing of target over 1 minute)
a. Advantages/Requirements:
i. requires no estimate of target AOB or speed prior to firing
ii. requires one rough range estimate, own speed, and the bearing change of target over 1 minute
iii. requires final range estimate to correct for parallax prior to shot, but can be roughly estimated
iv. can be used at long distances during the overhaul maneuver to obtain rough speed with a rough idea of target AOB without slowing and thus losing time in overhauling
v. can be used to derive actual target speed with solid knowledge of AOB
vi. allows more freedom of maneuver than Ausdampfverfahren as no requirement to keep a constant target bearing, and thus can be used for night surface attacks
b. Disadvantages:
i. Less accurate than the Ausdampfverfahren and plotting during the overhaul maneuver, and is thus best used when encountering the target forward of the beam (say at 45 deg AOB or so)
ii. not optimal when target AOB is small due to small target presented for the torpedo and need for appreciable bearing change

Of course, the results of either method are only valid if the target maintains course and speed. For both methods, a scientific calculator with trig functions (otherwise known as your WO standing near you working the slide rules) is also necessary.

I will preface this by saying that by no means are these original ideas; these methods are historical and come from the Torpedo-Schießvorschrift (torpedo firing provisions) from 1930. I credit my knowledge of these methods to the gentleman who put together this site:

http://www.tvre.org/en/acquiring-torpedo-firing-data

This site outlines the ins and outs of the real-life Torpedo-Vorhaltrechner (German TDC) as well as other ancillary information and is a must-read for all who haven’t yet. The page linked above details the methods of acquiring firing data and includes the methods I will be demonstrating below. Thus, I am merely compiling these methods below in a thread for ease of reference and implementation into SH3.

I will discuss each method in a separate post to follow.

[derstosstrupp]

Step 1:
Gain position forward of enemy’s beam. Submerge once a position sufficiently forward of the target’s beam has been achieved. Otherwise, at larger AOBs, a constant bearing may not be possible due to the low underwater speed of the sub. Not too far forward, however, that the target presents too sharp of an AOB – your eels will then have little surface area of the target to impact.

Step 2:
Achieve a collision course to target by either adjusting own speed or turning to or away so that the target bearing does not change.

Step 3:
Ideally, maintain this constant bearing for a period of 10-15 minutes, preferably the 10-15 minutes up to firing. 10-15 minutes allows you be sure you are truly on a collision course, however in practice you could get by with much less, perhaps 3-4 minutes. Use this time to set up your eels for firing (depth, pistol, outer doors etc).

Step 4:
Set up TDC for the shot.
1. With scope pointed at the target (collision bearing you’ve been hopefully maintaining), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.
2. Compute speed for the TDC as follows:
a. Own speed x sin(target bearing) = target speed to input into TDC. Remember, this is degrees from the bow, so if she’s constant at bearing of 330, the target bearing for this formula is 30!
3. Immediately prior to firing, obtain a range estimate and input into the TDC. Now toggle TDC to auto. This is a must to correct for parallax, or the error caused by the fact that you are not shooting torpedoes out of the lens of your periscope, unless of course the gyro angle is within 10 degrees or so of your bow, in which case parallax error is moot. Use whatever your GUI offers. I use Hitman’s top-notch GUI and thus only estimate using the scope reticles. This is more than sufficient. Just know that errors due to inaccurate range will be more pronounced the closer you are and the larger the gyro angle. Alternatively, you could start a turn toward the target once you obtain the gyro angle for the shot and pull the trigger once your bow crosses the zero gyro angle bearing, thus eliminating the need for the torpedo to turn and the need for a range estimate, but I have found this a bit unwieldy in practice.

Step 5:
Once at a good firing range, fire!

Nary was a mark or line or angle drawn on the map throughout this whole process. No information was needed from the rec manual either, although a rough knowledge of the target’s mast height is needed for a range estimate if at large gyro angles.

Below is a video demonstration of this method:

[derstosstrupp]

A note to modders/tech-savvy folks: The tvre.org site I linked above in the first post has an example of the slide rule for this method (see part about Auswanderungsverfahren “B”, toward bottom of page). It is relatively self-explanatory how this slide rule is used once you understand the guts of the calculation. Makman had mentioned in a post I’d seen about the desire to implement this slide rule in-game. I second that!

Step 1:
Gain position forward of enemy’s beam. Submerge once a position sufficiently forward of the target’s beam has been achieved. Otherwise, at larger AOBs, approach may not be possible due to the low underwater speed of the sub. Not too far forward, however, that the target presents too sharp of an AOB – your eels will then have little surface area of the target to impact.

Step 2:
Once you’ve nearly closed to firing distance, jot down your own speed (Ve), estimate range to target (E) and note the target’s bearing (b1). Start stopwatch. Do not alter own speed! The rest of this method only takes a couple minutes before firing, and so keep that in mind with respect to “nearly closed to firing distance”.

Step 3:
Once exactly one minute has passed, stop the stopwatch and note the new target bearing (b2). Do not move scope from this bearing until you fire for the rest of the method!

Step 4:
With scope pointed at (b2), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.

You now have 4 pieces of information noted: own speed (Ve), first bearing (b1), range at first bearing (E) in hectometers (this is important – take your range and divide by 100 and use this figure in the calculations), and second bearing (b2). Remember, this is degrees from the bow, so if she’s at bearing of 330, (b2) for this formula is 30! The change in bearing (b2-b1) we will call (w). Time to crunch numbers (in other words, time for your trusty WO to start spinning those slide rules, and thus pause is fine until you become proficient). Items in parentheses above are used to denote items in the formulas below.

Step 5:
Compute speed for TDC.
1. (Ve) x sin(b2) = (Vk). This represents the speed to input to the TDC IF WE WERE ON A COLLISION COURSE. We are not – the bearing is changing and thus we need to apply a correction:
2. (E) x 3.2967 x sin(w) = (d). Remember to convert your range (E) to hectometers by dividing by 100! The 3.2967 factor is to correct from metric to nautical miles since the correction (d) is in knots.
3. (Vk) +/- (d) = speed to input into TDC. If sub and target bows going in the same direction and the bearing change showed the target pulling ahead, you will ADD correction (d) to (Vk). SUBTRACT if sub and target bows are going the opposite directions, or if you are gaining on target (bows in same direction).

Step 6:
Obtain a final range estimate and input into the TDC (easily estimable since you got (E) already, just use judgment as to what the firing range would now be a minute or so later). After inputting, you should still be on (b2). This is a must to correct for parallax, or the error caused by the fact that you are not shooting torpedoes out of the lens of your periscope, unless of course the gyro angle is within 10 degrees or so of your bow, in which case parallax error is moot. Use whatever your GUI offers. I use Hitman’s top-notch GUI and thus only estimate using the scope reticles. This is more than sufficient. Just know that errors due to inaccurate range will be more pronounced the closer you are and the larger the gyro angle. Alternatively, you could start a turn toward the target once you obtain the gyro angle for the shot and pull the trigger once your bow crosses the zero gyro angle bearing, thus eliminating the need for the torpedo to turn and the need for a range estimate, but I have found this a bit unwieldy in practice.

Step 7:
While still on (b2), toggle TDC to auto, reacquire target and fire! You’re already at a good firing range. That is a benefit of this method – it is very quick once you get the hang of the calcs, all done immediately prior to firing.

There are also other handy uses for the Auswanderungsverfahren method, such as at long distances during the overhaul maneuver to obtain rough speed with a rough idea of target AOB without slowing and thus losing time in overhauling. In time, and if interest is shown by the community, I will post.

Below is a video demonstration of this method:


Enjoy and gute Jagd!

[Aktungbby]

derstosstrupp! After a two year silent run... Ausdampfverfahren und Auswanderungsverfahren! Jawohl!

[CybrSlydr]

Great post!!!

[sublynx]

I hail thee, Sir

I'll make a TGA or two about these methods, edit them into my SH3, and wait for the lucky day when the kids are old enough to hang around with their friends all the time - and then I'll have a blast learning these new - I mean old, but authentic - techniques

[scott_c2911]

Its a good post but I feel once the game is up and they start zig-zagging these methods will throw a few errors in. Educated guessing at that point is still a good method lol.

[danasan]

Tutorial of the year! Thanks a lot, mate.

[derstosstrupp]

Originally Posted by scott_c2911

Its a good post but I feel once the game is up and they start zig-zagging these methods will throw a few errors in. Educated guessing at that point is still a good method lol.

Absolutely valid point, Scott. For the Ausdampfverfahren in particular, as that requires a steady target course and speed over time to establish a collision course. These methods are really best suited against loner merchants that infrequently zig while you are undetected, however Auswanderungsverfahren could be suitable for convoys as the procedure is done immediately prior to firing. That said, hopefully one would already have convoy speed from the overhaul maneuver or contact reports!

[Aktungbby]

Originally Posted by scott_c2911

Educated guessing at that point is still a good method lol.

AuswanderungsverfeuernaufdemFlügel

[Magic1111]

@ derstosstrupp

Is it possible that you post all three posts in german words too? You are a german speaker, or?

For me it's too much English text to understand....

[derstosstrupp]

Originally Posted by Magic1111

@ derstosstrupp

Is it possible that you post all three posts in german words too? You are a german speaker, or?

For me it's too much English text to understand....

Gruß Magic,

Kann ich! Deutsch ist für mich Zweitsprache, habe ich als Kind gelernt. Das sollte mich aber nicht daran hindern, das alles zu übersetzen. Wird flott gehen, wenn ich mal Zeit habe. Das kann ich auf jeden Fall diese Woche machen.

Gute Idee! Würde doch ein Verbrechen sein, diese Methoden deutschen Gehirnen geheim zu halten, da sie schließlich auf deutsche Gehirne zurückzuführen sind!

[Magic1111]

Originally Posted by derstosstrupp

...
Gute Idee! Würde doch ein Verbrechen sein, diese Methoden deutschen Gehirnen geheim zu halten, da sie schließlich auf deutsche Gehirne zurückzuführen sind!

Vielen Dank, freue mich sehr!

[Magic1111]

Again @ derstosstrupp

Maybe you can post the german words manual here in the german subforum:

http://www.subsim.com/radioroom/forumdisplay.php?f=252

[derstosstrupp]

Auf Deutsch stehen die obigen Verfahren jetzt auch zur Verfügung!

http://www.subsim.com/radioroom/showthread.php?t=222400