I've been thinking too much

[washishu]

Earlier this year, after assistance and guidance from members here, I got SHIII up and running again on my MacBook. Playing the game again after a long absence revived my general interest and I have been re-reading Michael Gannon’s Operation Drumbeat and this has also revived something I’ve puzzled over in the past in reading this and the other sub-books.

It is accepted understanding that the WWII torpedo could be an unreliable weapon and so sub skippers of all navies involved did what they could to minimise these problems. The particular ‘problem’ that has always puzzled me concerns the angle of approach and attack and the consequent angle at which the torpedo strikes the target. In all ‘analytical’ explanations I have come across it’s stated that sub skippers would try to manoeuvre for a position at or close to a right angle to the target’s course, so that the torpedo gyro-angle was zero or close to zero and the hit would be at an angle of 90º or beam-on. Fine; that makes complete sense.

My puzzlement comes from the descriptions of the attacks in Drumbeat (and similar in Iron Coffins etc.) Even when, according to the description, there appears to be ample time for manoeuvring the target course, relative bearing and the AOB and the sub course etc. given in the description often appear to indicate a fairly flat angle, increasing the risk of the torpedo being deflected off the ship’s side.

In a sort of playful mood one Saturday morning, I used the Happy Times mission in standard SHIII to experiment. I chose it because the convoy course is an easy due east and the sub is in a perfect position from the start. So in a 45º approach, firing four torpedoes at gyro-angles of 355º, 358º, 000º and 005º, the first three all missed, passing ahead of the target, the fourth (005º) was a bow hit, but only just. Two of the misses went on to strike other ships in the convoy and were deflected. I assumed that this was due to the coding in the software being such that if the angle is beyond certain parameters the probability of deflection is greatly increased

I re-started and tried again. Same approach angle, 45º, three shots at 355º, 000º and 005º gyro angles. The first (355º) hit but forward of the aiming point. The other two passed ahead, but this was understandable as after the hit the target slowed and began a turn away.

My ‘experiments’ appear to suggest that SHIII more-or-less conforms to the accepted understanding. So how come there seem to be so many successful, much flatter-angled attacks in the books? Also in Drumbeat the accounts of attacks often include, for example, an ‘offset’—which I take to mean the gyro-angle—in the order of 15º or more and this appears to be by choice rather than forced.

Can anyone throw any light on these apparent contradictions?

[Nemo66]

Ahoy washishu,


my experiences in years of SH3 learned me, that there are two different approaches to a torpedo shot:

1. If you want to hit the target directly with a "direct hit ignition head" it is preferrable to hit the target mor or less rectangularly, otherwise the torp might just slip off.
This also happens if the torpedo is laimed to deep, because it slips off the ship's rounded structure near the keel
If you watch the impacts by free outside cam (F12) or with detected units cam ( the point or semicolon key) you can see it slip off which seems very close to real life physics to me. In fact, this is one of the best things about SH3 to make things realistic; in SH 2 every torpedo with a direct-hit-head that crossed the course of the target exploded no matter what angle.

2. If you use a "magnetic ignition head" things are totally different. The torp has to pass UNDER the ship at a depth of 1-2 m under the keel. If you do this in a rectangular way, the eel passes very fast under the ship, leaving the magnetic head not enough time to ignite, because you use only the width of the ship which is obviously much smaller that the length. The eel might not explode and just pass the target, or explode right behind the ship causing less damage. This happens especially when you use a T1 at 44knts in rough seas, because the ship goes up and down with the waves and it might happen, that it is going up right at the moment your torp passes, and the distance to the keel becomes to big to ignite. If it runs along with the keels direction, the ship goes down again while the torpedo is still underneath it and the eel will explode.
What i do to assure a clean magnetic hit is to shoot the eel in a very flat angle, almost paralell to the ships keel, say 15-30 degrees. The torp's way under the keel is a lot longer this way, so the magnetic head has a lot more time to ignite properly, as the eel runs more or less with the ships keel direction. Also i stay behind the ship and never fire when the ship is heading towards me, because this would also shorten the torpedos time under the keel as the two speeds of the target and the eel accumulate resulting on a smaller time-window for the collision.
If i let the ship pass and fire from the back this procedure gives the eel more time to ignite because the speeds diminish each other.

So a perfect attack (according to me) is to hit at first with a magnetic, flat angle attack form the back, then wait a little bit in order to give the target time to get flooded, and in the second approach i give him another one in a rectangular, direct hit way, and try to hit the ship at another compartment, not to close to the first hit, in order to create mximum destruction.
It's very hard to determine how the waterline of a ship changes after being hit and flooded to some extent, and therefore its very hard to hit with a second magnetic, as you don't know exactly how deep to fire. Especially with ships that sink to one side or sink via stern or bow this is very hard to do, so i always fire only one magnetic hit and do the rest with direct rectangular hits.

As the german torpedo crisis in 1942 when operation drumbeat took place was over, and the magnetic heads worked properly in this latitude, (and made much bigger damage , too), i could imagine that U-Boat captains did it pretty much the same, so i think that might be the answer to your question.

I hope i could "enlighten" you a bit :salute:

[sublynx]

Usually we tend to go for the straight torpedo run attacks as if the torpedo was a bullet or an arrow. The torpedo can however change its course after the initial launch, a bit like a tennis ball or a soccer ball can be hit with a curve. One can for example run alongside a ship and shoot the torpedo towards a ship that you see exactly to your right or left while moving to the same direction it is travelling. The reason we don't often do that is the need for accurate estimations and the fact that the eels fail us with the depth keeping and pistol already. The turning of the torpedo is yet another aspect that might fail. But if a launch like that succeeds the torpedo will hit the ship's hull at a 90 degree angle, even if the u-boat is not at a 90 degree angle.

[washishu]

I wasn’t questioning the real-world physics of torpedoes; I understand that with a small, curved surface striking a large, curved surface it would be surprising if the torpedo wasn’t deflected when hitting at a shallow angle. The purpose of my idle, Saturday morning experiment was to see if/how that was modelled in SHIII and it seems that it is modelled but how accurately I’m not sure. (I should maybe say here that on that particular Saturday morning I had nothing better to do and it was raining hard outside. I had thought to carry out a number of experiments at differing angles to see if there might be a span within which detonation was certain, another span beyond the first where probability of deflection increased and another span beyond both of these where deflection was certain. But after two or three trials I got bored and gave up thinking surely you can find something better to do with what remains of your life).

I also understand the reasons for the zero gyro-angle shot sublynx; the fewer variables there are, the greater the chance of success and so I also almost always try to get into that perfect position. The crux of my post—maybe I didn’t explain it well—was that, in reading the accounts in the books (on the occasion that prompted this it was Drumbeat but it applies to the other books too), the attack position appears to be a long way from perfect even when the attack was not a forced snatch-shot. Eg. “At 1244 Hoffmann had Malay where he wanted her: speed a surprising eleven knots, range 400, angle on the bow Green 21. Los! The last G7e left for a twenty-eight second voyage. . . “ and so on. My point is that I would have thought that an AOB of 21º at 400 metres was a far from perfect solution, but the preamble to this and the “. . . had Malay where he wanted her . . .” suggests that this was not a snatch-shot under difficult circumstances.

I hadn’t considered Nemo66, your very pertinent observations on the magnetic detonator characteristics, but I’d still maintain that, with all the uncertainties that you outline, it’s easy to be daring in a game when, if it goes wrong you can just shrug and have another cup of tea; it’s another thing entirely when your life depends on getting it right.

Towards the end of the book Gannon details an attack by U-123. Hardegen has only two torpedoes left, he’s stern-chasing a tanker but it’s fast and he struggling to catch it. So he takes a stern shot (“. . . U-boat’s speed at time of launch nine knots; own course 307 degrees; target’s course 350.5 degrees; torpedo’s course 318 degrees . . “) The expected explosion doesn’t come . . . but then, “. . . just as he bent to give a new course to the pipe the western sky suddenly erupted in a blinding red-and-yellow explosion”. Quite possibly this was just such a case as you outline sublynx (the set depth of the torpedo is given as only three metres but given the uncertainties . . .) Also, a course of 307º and torpedo course 318º suggests a gyro angle of around 10º and I wonder why, after over an hour of pursuit he didn’t come to 318º and have a zero gyro-angle to further minimise the variables of what he recognises is a risky shot. As much of the detail of these attacks is claimed to be taken from logs and war-diaries, it can’t easily be dismissed as author’s error or artistic license.

[sublynx]

I'm not enough of a mathematical wizard to tell from those values, but would it be possible that some of the attacks that are described in books and war diaries actually were calculated to achieve a 90 degree contact when the torpedo hit the ship - after the torpedo's gyro changed its initial heading?

I have played SH3 for a long time, intermittently though, and to me the fact that you can set the launch in a way that ends up in a 90 degree pistol - keel contact, even though the u-boat's course is far from perpendicular, is still new and hard to grasp.

Here's a link to those of you who like me are in the learning process in this kind of torpedo firing:

http://helmut.saueregger.at/gameresources/SH3/Contact%20Approach%20Attack.pdf

[washishu]

I haven’t seen that link before; thanks. I’m no mathematician either, in fact I get a bit nervous when confronted with too many numbers. I usually use what I refer to as the 90º method; establish target course (usually by just paralleling from first sighting); get ahead; come to a course at 90º to that course; set AoB to 90º when ‘scope/UZO at 000 (or 180); wait; shoot. It’s an almost guaranteed success; so much so that it can be a bit boring. I’d like to be more ‘hands-on’ about it but I’ve read that link three times and I understand only a fraction of it. I probably need to print it and just use it like a trained monkey a couple of times and maybe then it will start to sink in.

However it does go some way to explaining what was going on in the real world when the target course/position/speed etc had to be estimated without a computer to show you the target’s exact position on the chart.

[TorpX]

The crux of my post—maybe I didn’t explain it well—was that, in reading the accounts in the books (on the occasion that prompted this it was Drumbeat but it applies to the other books too), the attack position appears to be a long way from perfect even when the attack was not a forced snatch-shot. Eg. “At 1244 Hoffmann had Malay where he wanted her: speed a surprising eleven knots, range 400, angle on the bow Green 21. Los! The last G7e left for a twenty-eight second voyage. . . “ and so on. My point is that I would have thought that an AOB of 21º at 400 metres was a far from perfect solution, but the preamble to this and the “. . . had Malay where he wanted her . . .” suggests that this was not a snatch-shot under difficult circumstances.

...

Also, a course of 307º and torpedo course 318º suggests a gyro angle of around 10º and I wonder why, after over an hour of pursuit he didn’t come to 318º and have a zero gyro-angle to further minimise the variables of what he recognises is a risky shot. As much of the detail of these attacks is claimed to be taken from logs and war-diaries, it can’t easily be dismissed as author’s error or artistic license.

I think this is a matter of the real war being different than the game. In the game, target ships go straight, and do not zig, until they detect you. In the game, it is a simple matter to determine the AoB and range (at least if you are using map-contacts). In real-life, targets usually zigged frequently, and the AoB, and range had to be estimated on a hasty basis.

It is often easy to run ahead and maneuver for a 'perfect' set-up in SH, but in reality, the prospects of obtaining an ideal set-up were probably not nearly as good.

Moreover, the USN found during the war, that the gyro angle was not an important factor in hit percentages, for gyro angles of 40 degrees or less. I don't what the equivalent KM stats or conclusions were, but suspect they were not too much different.

[washishu]

You're probably right; and there's always the 'writer's license' angle too; Gannon does seem to make generous use of this.

I can't remember where I picked it up from, various sources I imagine, but I seem, over the years to have 'absorbed' the notion that the torpedo gyros of all participants were unreliable and so the angle was kept to a minimum. But maybe I just interpreted 'minimum' as zero when in fact it might have meant (say) 40º.

[sublynx]

I also think that SH3 might overestimate the pistol failures caused by the torpedo hitting at a non-90 degree angle.

[Tupolev]

I've never read the book, but I spend a lotof ttime reading KTBs on uboatarchive.net. They're incredibly interesting and helpful in playing realistically. It also gives you some insight into why some Commanders were hugely successful and some weren't. Hardegen's actions during his 2 East Coast patrols are incredibly gutsy. He'd usually close to 500m surfaced; as a result he only missed twice on his Drumbeat patrol!

http://uboatarchive.net/KTB123-7.htm

BTW that shot at Malay happened at dawn, Malay had spotlights on U-123, another steamerffiring starshells, and there was only 10m depth under keel. He had to fire and get the hell out of Dodge.

T

[TorpX]

I can't remember where I picked it up from, various sources I imagine, but I seem, over the years to have 'absorbed' the notion that the torpedo gyros of all participants were unreliable and so the angle was kept to a minimum. But maybe I just interpreted 'minimum' as zero when in fact it might have meant (say) 40º.

I dare say, if you made a survey of posts in this forum, you would come to that conclusion. SH players do seem to have that idea. It may be a matter of people thinking that because a certain set-up is ideal, that it was typical.




BTW that shot at Malay happened at dawn, Malay had spotlights on U-123, another steamerffiring starshells, and there was only 10m depth under keel. He had to fire and get the hell out of Dodge.

T

Yes, sometimes it is 'now or never'.



There is possibly one other thing to consider in this. That is human psychology. If your subs were having (or had recently) a large number of torpedo failures, it would stand to reason that skippers might be extra conservative in making attacks. Most of the time they would not know why their torpedoes were failing; only that they did. They might try to get 'perfect' set-ups to compensate for the shortfalls in the torps.