DW makes me wonder: How did WW2 subs find anything?

[Wisq]

Hi all,

I was playing some DW again today, taking on some of the missions for the first time. In the San Diego Breakout mission, I was happily TMAing the FFG via its active pings. Easy peasy when they give you such a regular, crisp signal, eh? But aside from the actives, I wasn't picking anything up whatsoever on passive, even the towed array, for the entire mission.

(I don't know how close we got, but the truth layer says we started at 8 NM apart. That's a tiny tiny portion of the whole US West Coast map, which is basically just California anyway. Oh, and there was no layer to speak of.)

Now, I've also played a lot of Silent Hunter, particularly SH4. And while some of my intercepts were convoy reports supplied by HQ, a lot of them were just "hey, I'm puttering along and I pick up a ship on the hydrophone". I don't recall the exact distances I could hear them at (and I don't have a truth layer to check), but it always seemed pretty darn far. Plus, the ocean is a huge place, so for me to be picking up ships on a regular basis, the detection distance must be pretty high.

So, long story short, this got me wondering — if modern, high-tech, computer-aided super-multi-frequency passive sonar can't pick up a surface ship chugging along at 5 to 8 knots only 8 NM away, how the heck did anyone ever find anyone else in WW2 (and in SH3/4)?

I've got a bunch of theories — and I imagine it's some combination of these — but I'm curious if anyone happens to know what exact combination it is:

1. Maybe detection range is just unrealistically long in SH. (But I've played with lots of realism-enhancing mods, and I can't imagine they would let this slide, unless the gameplay was just broken without it.)

1(b). Maybe it's the thermal layer — I know there are situations where you can hear things at huge distances due to thermocline refraction. I believe this would be a transient thing and would come and go, which is not what actually happens in SH, but maybe SH can't model that and so they just gave the hydrophones longer ranges to emulate it.

2. Maybe surface ships, particularly military ones, are just a lot quieter now. This certainly makes some sense to me — it always seemed like I was mostly picking up ships by their engine and propeller noises, and we have much better engine and propeller designs today.

3. Maybe it was just that everything was so shallow. Most of the mission, I was cruising in depths of only 50m or less. I seem to recall that shallow water makes sonar trickier, mainly because of its acoustic properties but also because you can't stream the array very far.

4. Maybe it's just time compression — with DW only doing a few levels of it, whereas SH goes up to 8192x compression and missions span months of travelling at max speed, it's just inevitable that I would encounter something on a regular basis, even if it takes days between encounters. Whereas my DW missions take a few hours, max.

5. Maybe there's just a ton of traffic in SH, or they intentionally spawn stuff near you. I think I recall someone (Ubisoft?) mentioning that the campaigns were reasonably realistic except that you would see a lot more action than was truly realistic. But I might be thinking of Falcon 4.0 instead …

6. Maybe it's all in my head. Maybe the SH distances just seem longer because the subs are so bloody slow. Maybe the DW distances just seem shorter because I'm looking at the entire US west coast. (But, I pulled up Japan on Google Maps, and the distances I seem to recall detecting ships at are still pretty large.)

7. Shipping lanes. If they're used heavily and I pass through them regularly, maybe there's just a good chance of inevitably encountering something on a semi-regular basis.

8. Maybe there was just a heck of a lot more shipping back then. I mean, nowadays so much stuff goes by plane, and shipping is just for bulk cargo. (But then, there's so much economy today that I would imagine this balances out and then some …)

… and possibly more aspects I haven't thought of.

So. Any insights? Just curious. I'm actually thinking it's probably mostly #4, time compression — just the sheer luck of running into things when your missions span months of travel, rather than hours.

[Aktungbby]

Wisq! After a three year silent run!

[SilentPrey]

It doesn't sound to me like that mission has any civilian traffic modeled. According to marinetraffic.com there are at least a dozen vessels between San Diego and San Clemente Island right now; 74,167 ships live now worldwide. I don't know what percentage of shipping they actually track but I doubt very highly that it's one hundred. So, you should have run into merchant shipping but didn't.

Manual sonar operation in SH4 gives you best set, best conditions performance no matter what. Basically, if it's in render range you can hear it. That said; that range figure does seem to be pretty accurate for the gear installed on the fleetboats at the end of the war. I didn't look into it myself but recall reading somewhere that they did a decent job of that.

Modern warships probably are MUCH quieter than WWII merchants. However, DW has a hardcap on passive detection range. LwAmi removes it but I don't know about any of the other mods. The LwAmi manual doesn't say what the hardcap was but it's very possible that eight miles is outside of it.

Also, in SH4 you're not looking for any particular ship; pretty much anything displaying a meatball is acceptable while hardly anyone puts any 'extra' enemy ships into a DW mission. I play SH4 with RSRDC (historical traffic) and still run into plenty of victims.

So, I'd say it's a function of time compression and inaccurately low amounts of traffic in DW missions that's got you thinking that.

[Mike Abberton]

Hello,

Sub warfare in World War 2 was a whole different ball game than modern day sub warfare.

Primary sensors to locate targets were generally lookouts (esp. German and Japanese) and Radar (US). They traveled known shipping lanes/hunting zones and received steering guidance from other sources.

For the US, radar was key because Japanese merchant traffic was not generally escorted and even when it was, the Japanese had very few radar warning receivers on its ships or airplanes. You could spend most (all?) of your time on the surface illuminating and noone was going to counterdetect you.

Of course the game distorts our perception of modern warfare a bit by generally starting us off semi-near (close to or in sonar range) our targets/opponents. There is no open campaign mode like in Silent Hunter 3 or 4.

I think even in the modern warfare, there would be a lot of steering guidance given to subs either in mission orders or on the fly through satellite communications on where the targets are. In a conventional WWIII scenario (like Red Storm Rising), a Russian nuke boat is probably going to find convoys through external means (communications), not drive around solely looking on their sonar displays.

Mike

[Wisq]

Originally Posted by Aktungbby

Wisq! After a three year silent run!

Haha, yeah, I've been lurking now and then but haven't had much to post. Sub/naval sims aren't getting the love they deserve these days.

Originally Posted by banryu79

For DW, there is an old thread by Dr.Sid that examine the whole thing, here: DW sound propagation model measurements

EDIT: I think you could find very intresting this thread too: Underwater acoustics for dummies

The modeling of the sensors/acoustic environment in SHx is crude at best if confronted with DW... But that's fair, IMO.

Even so, after a year playing SH3 I recently starded the desire to improve a little the "hydrophones aspect" in SH3. I installed the "New Sh3 Hyprophones layers by Rubini v2.0" mod and that made the trick for me. Nothing revolutionary, mind you, but something very worthwhile IMO that give the game more substance

Nice, thanks for the links! I'll have to check out the current mod situation for the SH games … I imagine it's changed some in the years I've been gone, especially since there hasn't really been a worthy successor.

Originally Posted by SilentPrey

It doesn't sound to me like that mission has any civilian traffic modeled.

Oh, yeah. Sorry, I should've clarified: My confusion was that 8 NM seemed like a short distance to not be able to hear a surface ship (even a military one), not just "where are all the contacts?"

Personally, I suspect they said "you're trying to escape, civilian traffic will just make your life easier, we'll say it's a quiet day and/or they already told the civ traffic to scram". Or they just forgot.

Modern warships probably are MUCH quieter than WWII merchants. However, DW has a hardcap on passive detection range. LwAmi removes it but I don't know about any of the other mods. The LwAmi manual doesn't say what the hardcap was but it's very possible that eight miles is outside of it.

Oo, good point. I forgot that I was running vanilla, not LwAmi. I was so excited just to finally be able to run it again (having discovered the Direct3D hack that lets it run on Win8).

Originally Posted by Mike Abberton

Primary sensors to locate targets were generally lookouts (esp. German and Japanese) and Radar (US). They traveled known shipping lanes/hunting zones and received steering guidance from other sources.

I do recall that standard (game) procedure (once you reached your patrol area) was to putter along for <x> hours on the surface, then dive and check for contacts, then surface and repeat. Particularly in bad-weather situations. But yeah, being unable to stay submerged for too long — or be in any condition to fight if you did stay submerged for long and then picked something up — certainly made the eyeball, radar, and radio the primary methods of acquisition.

Of course the game distorts our perception of modern warfare a bit by generally starting us off semi-near (close to or in sonar range) our targets/opponents. There is no open campaign mode like in Silent Hunter 3 or 4.

I think even in the modern warfare, there would be a lot of steering guidance given to subs either in mission orders or on the fly through satellite communications on where the targets are. In a conventional WWIII scenario (like Red Storm Rising), a Russian nuke boat is probably going to find convoys through external means (communications), not drive around solely looking on their sonar displays.

Makes sense. Certainly today, I'm guessing we'd have planes and satellites doing the target-finding, and subs would just be treated as a strategic and tactical support resource rather than the primary hunters.

[tmccarthy]

Originally Posted by Wisq

So, long story short, this got me wondering — if modern, high-tech, computer-aided super-multi-frequency passive sonar can't pick up a surface ship chugging along at 5 to 8 knots only 8 NM away, how the heck did anyone ever find anyone else in WW2 (and in SH3/4)?

Hi,

It seems that "Ultra" code breaking and radio interception played a massive part in the Submarine war during WW2 in the Pacific.

I'm reading "Silent Victory: The U.S. Submarine War against Japan" by Clay Blair. It appears to cover every noteworthy US Submarine war patrol for the entire war.

I was very surprised at how often, a majority of the time in patrols covered, US subs received intelligence on Japanese convoys, ship movements and warship activity. US code-breakers were able to read the Japanese maritime codes and military codes from the very beginning of the war, with information like ships "noon position" and destinations. Sub Captains would sometimes report something like "contact one hour early or late". But many warships and hundreds of transports were sunk with the use of Ultra intelligence.

Also by the time Submarine Captains returned to base the Admirals in charge would often have radio intercepts verifying sinkings and often would know more about the patrol's success than the Sub Captains themselves.

At least two German U boats bringing supplies and technology to Japan were also sunk by US subs with Ultra intelligence.

-It's a good book...

-Tim

[banryu79]

I vote for the following points:

Originally Posted by Wisq

1(b). Maybe it's the thermal layer — I know there are situations where you can hear things at huge distances due to thermocline refraction. I believe this would be a transient thing and would come and go, which is not what actually happens in SH, but maybe SH can't model that and so they just gave the hydrophones longer ranges to emulate it.

2. Maybe surface ships, particularly military ones, are just a lot quieter now. This certainly makes some sense to me — it always seemed like I was mostly picking up ships by their engine and propeller noises, and we have much better engine and propeller designs today.

3. Maybe it was just that everything was so shallow. Most of the mission, I was cruising in depths of only 50m or less. I seem to recall that shallow water makes sonar trickier, mainly because of its acoustic properties but also because you can't stream the array very far.

About #2
True, back at that time they didn't have the know-how and the technology to perform DSP on the acoustic signals... The signal was processed by a pair of human ears.

But on the other side the ships, even military ones, did a lot more noise (orders of magnitude).

And then there is the difference in how the two different games (I dond't know directly SH4 but I assume it is identical to SH3, the one that I know) model the sensors/acoustic environment aspect... And it is here that we find the greatest difference.

For DW, there is an old thread by Dr.Sid that examine the whole thing, here: DW sound propagation model measurements

EDIT: I think you could find very intresting this thread too: Underwater acoustics for dummies

The modeling of the sensors/acoustic environment in SHx is crude at best if confronted with DW... But that's fair, IMO.

Even so, after a year playing SH3 I recently starded the desire to improve a little the "hydrophones aspect" in SH3. I installed the "New Sh3 Hyprophones layers by Rubini v2.0" mod and that made the trick for me. Nothing revolutionary, mind you, but something very worthwhile IMO that give the game more substance (now, every time a get a contact in the hydrophones I can get away with a rough estimation of its range and in some tactical situations I have to choose between going down and listen better VS staying at PD but with a limited detection area).