Long lance torpedoes

[Mark V]

However if one had the choice of smaller weapons with say a similar speed and a range of 30,000 yards or less then in most cases the answer would be no. Especially if said smaller weapons were not oxygen powered.

Hi.

53cm envelope. Range 30.000 yards or less with 40 knot ?? speed.

That kind of range would require substantially enriched air (oxygen wise), 100% oxygen, or hydrogen peroxide as an oxidant. With plain air that is clearly impossible, even with todays technology.

Over 40% oxygen content in "air" is quite nasty. So is H2O2.

There is no way around it. Every time you want to squeeze SERIOUS performance from torpedo, you need lots of chemical energy. And every torp carrying significant amount of potential chemical energy is bound to be an dangerous device, atleast aboard when there is damage and fire on own naval asset.


Regards, Mark V

[LWD]

My thought here was that with a smaller torpedo the DD's could carry more. Perhaps the best bet would have been to have had two torpedos with as many parts in common as possible and use O2 for one and air or enriched air for the other. Then when you really need the range (vs the BBs) use the O2 model other wise use the air or enriched air version. In those cases you could probably make do with ranges of under 20,000 yards. Hit probabilites go way down after that anyway.

[caramut]

My thought here was that with a smaller torpedo the DD's could carry more. Perhaps the best bet would have been to have had two torpedos with as many parts in common as possible and use O2 for one and air or enriched air for the other. Then when you really need the range (vs the BBs) use the O2 model other wise use the air or enriched air version. In those cases you could probably make do with ranges of under 20,000 yards. Hit probabilites go way down after that anyway.

And today's dumb question from someone who knows nothing about the details is:

At 4 miles range, in submerged daylight attack with a target ship following normal patterns to avoid the risk of torpedo attack and all the variables of current and thermal layers causing fluctuations in torpedo speed and accuracy, and the sub being just a poofteenth off in sighting when firing, what were the chances of hitting a ship a few hundred feet long?

[Mark V]

And today's dumb question from someone who knows nothing about the details is:

At 4 miles range, in submerged daylight attack with a target ship following normal patterns to avoid the risk of torpedo attack and all the variables of current and thermal layers causing fluctuations in torpedo speed and accuracy, and the sub being just a poofteenth off in sighting when firing, what were the chances of hitting a ship a few hundred feet long?

No dumb at all. That is real hard one

The U-boatwaffe would knew it to few percentages. The knowledge from them is somewhere deep in Norfolk, St. Petersburg, and London archives.

I take the bull by the hornes and try. Don't laugh at me.

My guesses:

- That is very long firing distance for WW2-era submarine. Around 7 minutes torpedo run even with the latest, warmed up late-war electric torpedoes, almost at their max range.
- U-boat captain would surely seek better firing position, if escorts or speed of target would not prevent it. Only high value target would had been tried with that kind of firing situation in early/mid-war.
- Only diminutive proportion of U-boat launches would be made from distance like that before 1943.
- Even 1000m mistake in estimation of range would mean that even slow 11 knot freighter cover around 3 times its waterline lenght at same time torpedo needs to cover that 1000 metres.

With very, very good crew and captain:

My guess is that with 1 torpedo theoretically 33%, cut that half in real world.

With 4 torpedo spread, if the target is not making its turn right during the torpedoes running time 1 hit with 2/3 propability

- but because all ships did zig-zag - cut that in half.

4 torpedoes launched. 1 hit every third attempt in such scenario.

4 miles is very much for submarine without true range finding equipment and firing 30kn electric torpedoes. One quarter / one half of the range asked would be much more representative of firing solutions U-boats took, when they had the opportunity to manouvre.


Mark V


Disclaimer: I did not want to dwell on this calculation several days. So this is what 10 minutes of thinking got me - and i don't even dream to claim it is somewhere near the truth.

[Wargames]

And today's dumb question from someone who knows nothing about the details is:

At 4 miles range, in submerged daylight attack with a target ship following normal patterns to avoid the risk of torpedo attack and all the variables of current and thermal layers causing fluctuations in torpedo speed and accuracy, and the sub being just a poofteenth off in sighting when firing, what were the chances of hitting a ship a few hundred feet long?

4 miles is only 7,000 yards in range (Although most submarines used their stealth to close to 4,000 yards.). I would guess/estimate a probability of a hit from luanching a single torpedo to be 50%.

The higher the speed of the torpedo, the greater the chances of a hit.

Most statistics for hits would probably be based on German and Italian torpedoes first, followed by British and American, followed by Japanese (They didn't get many opportunities.).

[Mark V]

4 miles is only 7,000 yards in range (Although most submarines used their stealth to close to 4,000 yards.). I would guess/estimate a probability of a hit from luanching a single torpedo to be 50%.

Our guessimates are really far of each other

Mark V

[Wargames]

Mark V, we both saw the same problem - Why would a submarine launch at 7,000 yards instead of 3-4,000 (or les)? It would be hard to find statistics for submarine torpedoes launched at that range because so few would have been. I doubt that, at 7,000 yards, a single torpedo would even be tried.

Factors affecting the chances of getting a torpedo hit on a ship are:

1. The torpedo crew's skill in setting torpedo solutions,

2. The relative speed of the torpedoes,

3. The number of torpedoes fired,

4. The range to the target,

5. The relative direction of the target's movement,

6. The velocity of the target's movement.

I assumed a perfect beam shot with no zig-zag, target speed of 9-11 knots, and good torpedoes and optics to get maximum probability. But "real world" is much different. It would appear from my review the chances of a torpedo hit at 4,000 yards under war time conditions from a submarine were about 65% (My estimate - no cite). So I suppose 7,000 yards would be about 30% and not the 50% I originally offered.

And, as the quality of the torpedo drops, so does the 30% figure. For example, US aerial torpedoes dropped at just 800 yards only had about a 7% hit rate!

[caramut]

The reason I picked four miles is, embarrassingly, because I'm used to metrics and my rusty memory confused the 5,280 feet in a mile with the 1,760 yards. So I divided 20,000 yards by 5,000 and came up with 4 miles.

Anyway, the point of my enquiry was why build a torpedo with such a long range, be it 4 or 10 miles as I assumed that accuracy would drop off exponentially with greater ranges?

As I don't know how much space or weight was taken up by propellant, I'm not sure if it made much difference to the size and weight of the torpedo but if it did then wouldn't it have been better to build smaller ones with shorter and more realistic ranges?

[Wargames]

The reason I picked four miles is, embarrassingly, because I'm used to metrics and my rusty memory confused the 5,280 feet in a mile with the 1,760 yards. So I divided 20,000 yards by 5,000 and came up with 4 miles.

Anyway, the point of my enquiry was why build a torpedo with such a long range, be it 4 or 10 miles as I assumed that accuracy would drop off exponentially with greater ranges?

As I don't know how much space or weight was taken up by propellant, I'm not sure if it made much difference to the size and weight of the torpedo but if it did then wouldn't it have been better to build smaller ones with shorter and more realistic ranges?

Okay. First, I don't think any submarines in WWII had torpedoes with 20,000 yard range. The Japanes "Long Lance" was carried by surface ships.

At 20,000 yards, you actually had a chance of a hit with these weapons for three reasons:

1) The Japanese ships were launching 12 torpedoes each with reloads. Put 144 in the water and a 5% hit probability becomes 7 hits.
2) The torpedoes were very high speed for that range which improved accuracy.
3) US battleships could be expected to be "in line" and not evading torpedoes they felt they were out of range of (zig-zagging interfered with their own gunnery). Launching from an angle (closwer "bow on" versus "beam on"), if you aimed for the second ship in line and missed, you might still hit the first ship ahead of it or the third behind. Thus, 5% odds became 15% odds. Now we have 21 hits and that's a lot of damage.

[caramut]

Okay. First, I don't think any submarines in WWII had torpedoes with 20,000 yard range. The Japanes "Long Lance" was carried by surface ships.

At 20,000 yards, you actually had a chance of a hit with these weapons for three reasons:

1) The Japanese ships were launching 12 torpedoes each with reloads. Put 144 in the water and a 5% hit probability becomes 7 hits.
2) The torpedoes were very high speed for that range which improved accuracy.
3) US battleships could be expected to be "in line" and not evading torpedoes they felt they were out of range of (zig-zagging interfered with their own gunnery). Launching from an angle (closwer "bow on" versus "beam on"), if you aimed for the second ship in line and missed, you might still hit the first ship ahead of it or the third behind. Thus, 5% odds became 15% odds. Now we have 21 hits and that's a lot of damage.

Thanks for that.

Now it becomes clear.

I suppose the extra range helped a bit if there were two lines of ships, as a torpedo that missed the first line might get lucky on the second.

[LWD]

In surface engagements their was also a tendency to fire much larger spreads of torpedos. Also in most cases torpedos had two speed settings. If one was used on DDs and subs the subs probably would have used only the high speed setting. I recall reading somewhere (on this forum I think) that U-boat captains tried to get withing 1,00 yards (or perhaps meters) of their target. My impression is that even at this range they didn't have a 50% p(H) but I don't have any mumbers to back that up. Starting a thread on sub torp hits, misses, and ranges might be v ery illuminating.

[Mark V]

Hi.

Mark V, we both saw the same problem - Why would a submarine launch at 7,000 yards instead of 3-4,000 (or les)?

I would say that typical warshot in early/mid war was around 1000-1500 metres. If possible, subs gladly closed to well under 1000 metres.

2000-3000m range shots were taken, with some success. Beyond that, any success would be stroke of good luck.

Starting 1943 the Allied ASW forces made closing targets extremely difficult, and Germans were forced to launch from poor firing positions.


Mark V

[Mark V]

In surface engagements their was also a tendency to fire much larger spreads of torpedos. Also in most cases torpedos had two speed settings. If one was used on DDs and subs the subs probably would have used only the high speed setting.

Hi.

Also atleast RN and USN used shorter - around 6-6.5m lenght torpedoes in their subs, and longer in destroyers and cruisers, even if they shared the common 21in diameter.

Submarine torpedo tubes were designed accordingly, and could not use the longer models.

Germans, USSR, Italians, Dutch and Poles atleast used common lenght (mostly 7.2 metres) between their submarine and surface fleet torpedoes, with atleast 2 speed settings available. Subs used shorter range, higher speed setting, because with their limited fire control equipment, the longer range offered by lower speed setting would be an waste anyway (German G7e electric torpedo was not used by surface forces, but wet-heater G7a was used by both, surface vessels and U-boats).

Ofcouse for example Brit torpedoes shared large percentage of their components even if they had different overall lenght. The extra lenght gave more room for air vessel, and longer range.

That also in part answers caramuts question: Why torpedoes with range from where submarine would not hope to archieve an hit were fielded ?? Some countries shortened the sub torpedoes by a little for gains in saved space and weight, but with penalties in complicated logistics.

Some countries used basically the same torps for all their naval assets, and destroyers really needed minimum 8.000-10.000 metres range for their torps to have any realistic chance of firing opportunity against enemy cruiser or BB, those having good optical systems and steady gun platform.


Regards, Mark V

[Mark V]

Now it becomes clear.

I suppose the extra range helped a bit if there were two lines of ships, as a torpedo that missed the first line might get lucky on the second.

You can see carrier Wasp burning in distance. The closer vessel is destroyer O'Brien.

This is an extreme example. Wasp, and North Carolina plus O'Brien could not be said to sailed in "battle-line". They were far away of each other.



One carrier, one battleship and one destroyer all hit with one submarine 6 torpedo salvo. I-19 almost got 2 carriers, as also Hornet was almost hit.

OK. That was one REALLY lucky shot.

http://www.battleshipnc.com/history/bb5 ... subi19.php
http://www.chinfo.navy.mil/navpalib/shi ... ploss.html
http://www.combinedfleet.com/I-19.htm

picture: http://www.wlb-stuttgart.de