Two Historical Firing Methods (Hit What You Are Aiming At Without AOB or Speed)

[palmic]

Hi derstosstrupp:

I have one question about Ausdampfverfahren (Constant Bearing to Target)

At tvre.org i red the article you referred (awesome, thanks ) and found that this method is there described a little more simple.
It says they actually used (own heading - current target bearing) for target AoB and own speed for its speed. This way you dont need to calculate law of sine for 90 degrees AoB as you described.

Does your solution here have some advantage? For instance - you dont need to set accurate distance to TDC? Thanks

[siege00]

Here's a whole bunch of theorizing about why both methods would work.

I don't have all the maths behind it but from calculating and sketching these are my theories (not proofs).

1) Derstosstrupp's implementation of the (ausdampfverfahren) method works by simulating that the target is at a 90° angle on the bow. If you draw the triangle from yourself to where the target would be at 90° AoB, the torpedo path passes through where the target actually is so you've shortened the distance that the torpedo has to travel but still along the same path and intersecting the target's path in the process. If that's accurate then the torpedo run times projected by SH should be wrong since the target isn't actually making the triangle that the TDC thinks it is. It's being shorted.

2) With what the article says about how it was in practice, it's the same methodology but for an isoceles triangle instead of a right triangle. Entering that the target is running at the same speed sets a factor of the triangle. If ownship and target truly had the same speed then ownship and target should also have the same AoB (ie. forming an isoceles triangle), but since you're setting the target bearing as AoB, then the triangle is adjusted accordingly either shortening or elongating the shot.

Method 1 above uses the math directly while method 2 is a natural implementation of the math. Both still use the basic formula.

Does that make sense or did I just go too geeky? lol -- Again, I haven't proved it out on paper... just theory as to why both methods work.

[derstosstrupp]

Originally Posted by palmic

Hi derstosstrupp:

I have one question about Ausdampfverfahren (Constant Bearing to Target)

At tvre.org i red the article you referred (awesome, thanks ) and found that this method is there described a little more simple.
It says they actually used (own heading - current target bearing) for target AoB and own speed for its speed. This way you dont need to calculate law of sine for 90 degrees AoB as you described.

Does your solution here have some advantage? For instance - you dont need to set accurate distance to TDC? Thanks

Hi palmic,

You're right, the article doesn't expressly mention using 90 deg AOB for the Ausdampfverfahren method. It's really a matter of taste - you can either use the collision bearing as a proxy for AOB, which eliminates the need to compute "target speed" using sines (I.e. own speed x sin(target bearing)), or use 90 deg AOB, in which case the above formula would be necessary.

To answer your question about advantages: What may prove difficult with just using the bearing as AOB is the relative difficulty of entering the exact bearing into the AOB dial of the German TDC, as it only displays in 10s of degrees. 90 deg is easier to input exactly on the dial.

[palmic]

Originally Posted by derstosstrupp

Hi palmic,

You're right, the article doesn't expressly mention using 90 deg AOB for the Ausdampfverfahren method. It's really a matter of taste - you can either use the collision bearing as a proxy for AOB, which eliminates the need to compute "target speed" using sines (I.e. own speed x sin(target bearing)), or use 90 deg AOB, in which case the above formula would be necessary.

To answer your question about advantages: What may prove difficult with just using the bearing as AOB is the relative difficulty of entering the exact bearing into the AOB dial of the German TDC, as it only displays in 10s of degrees. 90 deg is easier to input exactly on the dial.

You can use any AoB into TDC exactly, just set it to 90, lock and move periscope by (90 - your_wanted_AoB) degrees.

Its because of all triangle inner angles sums into 180.
So if you watch target moving 1 degree to the side, his AoB is changing also by 1 degree in virtual triangle solution.

[palmic]

I was thinking about how to use it immersively just on paper, or even in head and found easy helper for Auswanderungsverfahren.

When you calculate distance with bearing change into resulted speed modification where author of tutorial video is converting from metric system into speed (knots), just use 10 for every 300m of distance.

His distance was 1000m and he calculated in calculator result of 33.
By this hint 1000m is 300m * 3.3, so 3.3 * 10 as i said is the same

Sinus is 0.1 for every 6 angles from zero to about 30 then its a little different, you can print sin table from internet.
- sin(6) = 0.1, sin(12) = 0.2, sin(30) = 0.5.

In his example sin(10.5) = 0.18, so his example can be simply calculated in head like 33 * 2 / 10 minus some little portion -> 6.6 minus lets say 0.2 = 6.4.

Good enough for my TDC