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Originally Posted by neilbyrne
Ducimus, your eminence, I have been playing SH since the original and your TMO mod is just wonderful. You are indeed a talented guy.
I was just going to leave it at that because I did not want to alloy my praise with suggestions, but the detail of the mod and the enormous number of things that are rendered correctly indicated to me that you are most interested in accuracy and so would not mind the following. Some is just background with a couple of suggestions and maybe a question or two.
Just a little about my background so you don’t think that I’m pulling this stuff out of whole cloth. I’ve been a lifelong student of naval history and that was before I ever entered the navy. I am a retired Captain USN with 31years on active duty. Eighteen of those years were spent in ships, mostly destroyers. I was privileged to command a frigate, BRONSTEIN, and a destroyer, BRISCOE. So my actual experience of submarine warfare is on the ASW side. Or as it is jokingly called in the USN, Awfully Slow Warfare.
I was CIC and then ASW officer in BROWNSON and attended both of the associated schools in the early ‘70s. At that time, most of the US fleet was still not equipped with the Navy Tactical Data System (NTDS) which put many of our sailors at computer consoles and automated a lot of the detection and tracking functions. Ours was what was then called a “grease pencil CIC”. Even air tracks were plotted on large Plexiglas status boards called vertical plots (VPs). VPs came in two flavors, informational and tactical. The info VPs were for displaying all manner of data so the watch standers didn’t have to keep it in their heads. This was stuff like radio freqs and handset stations, call signs, threat emitter signatures, formation guide, speed and spacing, etc. These VPs were unattended and only updated as reqd. The air plot VP was only manned in exercise or real world situations when we cared about the air picture. It was manned by two radarmen (RDs), now called operations specialists (OSs). They would stand behind the plot to be out of the way and write backwards in white grease pencil. When we were training kids to do this, we would always tell them, “Don’t scrub off the whole tail.” That meant to leave enough track history on the plot’s tracks so anyone could glance up and see quickly what was going on. The marks were normally an arrow in the direction of movement and a connecting line to the last mark, like so: <-<.
ASW was never done on a VP, and to my knowledge was never done so in submarines either. We were equipped with two plotting tables. The older one was the Dead Reckoning Tracer (DRT); the newer was the NC2 which was stood for Navy Canadian plotter #2 after the inventing navy. The DRT was more reliable; the NC2 had more capability when it was working. Both used a moving “bug”, essentially a compass rose shining up from inside the table with a cross in its center representing own ship. The tops of both tables were glass and the RDs covered them with large sheets of tracing paper. In an ASW situation, the plot was manned by a minimum of four watch standers, the ASW evaluator (an officer) who was calling the shots. There was a TACOM, tactical communicator (junior officer or a petty officer). There were two plotters, north and south, junior petty officers or strikers. The south plotter was connected by sound powered phones to sonar and his job was to plot own ship (in black pencil) and own ship’s sonar contacts (in red pencil) at no more than one minute intervals. The north plotter was connected to the surface radar operator and the Anti-Submarine Air Controller (ASAC) if we were controlling an ASW aircraft. The north plotter’s job was to plot friendly ships (in blue) and their sub contacts (in red). Aircraft were not put on the plot except for helos when dipping their sonars, but any sonobouys dropped by a/c were plotted and all a/c symbols were plotted in green pencil.
A long explanation, for what is a relatively minor quibble. TMO replaced the unrealistic shp.dds red hull silhouettes with a black grease pencil mark. My experience in talking to submariners was that they also kept the tactical plot on the plotting table in the control room, not on a VP. So my vote for a shp.dds replacement symbol would be something like the “don’t scrub all the tails” VP symbology, two arrowheads connected by a line <-<. And since it’s the enemy, in red.
Next, I’d like to go into sub detection by escorts with sonar, visually and later with radar. Here I have a lot of experience, and it is very difficult. This is why between us and the Brits, we built 1600+ destroyers/escort vessels in WWII. There is strength in numbers, because the individual capability just sucks. In ASW School, we were taught the capabilities of all the sonars then in the US surface fleet. There were still some WWII ships active, mostly old FLETCHERs and SUMNERs, that hadn’t been through the FRAM (Fleet Rehabilitation and Modernization) refit that installed newer systems. As I recall, these old girls had the SQS-46V sonar. We did a day or two in the attack trainer using this system. In absolutely beautiful water, isothermal (no layer) to 400ft, it had a reliable detection range of 2000-2500yds. Now remember this was the best sonar we had toward the end of WWII. In worse water, it was less. And a good rule of thumb about subs below the layer is that range across the layer is no better than 33-25% of range above the layer. The IJN had nothing better than this, and in my research in Morison’s 15 volumes History of USN Ops in WWII and Roscoe’s histories of US Sub & DD ops, I never found a sub detection at greater than 2,500 yds on active sonar, and most IJN detections were at 2,000 or less. On passive sonar, those sonars could detect thermal (steam) powered torpedoes pretty well but close. The only condition when a sub on her battery would be vulnerable to passive detection though was if she were cavitating her screws, normally at 7kts or more and only above 150ft, or at 15kts or more above 300ft. Deeper than 300ft, water pressure keeps the cavitation bubbles from forming.
Max sonar speed for WWII ships was 12 knots and it was not graceful degradation above that. Go faster, and you were deaf as a post in both active and passive.
OK, so that’s sonar detections. How about visual? Very hard and you get lots of false contacts. For most of my time as a junior officer, seniors kept telling me that periscope detections by lookouts were a training problem. Then I got a look at about 30 years of exercise results and the opportunities vs. detection numbers were just dismal. Obviously, I can’t put classified numbers out here, but suffice it to say that the US Navy has finally decided that this is a job for a machine.
A warship has about seven folks looking out full and part time. Three are full time lookouts, port, stbd and aft. Then you have the OOD and JOOD who look out when they can. Last you have the two signalmen who are supposed to be looking out when not signaling; although, in fact, they hardly do. The lookouts have 120 degree sectors that do not overlap. The officers, when they are looking, normally search the forward 180 degrees. The aft lookout has no one else looking where he searches and his primary responsibility is to be the last line of defense for a man who falls overboard, so often he is searching in the near field which the others are not.
In eighteen years of sea duty, I saw three visual periscope detections that actually turned out to be submarines. Now admittedly, we weren’t worried about being torpedoed, and so our attention was less focused than that of our WWII brethren, but still, not great. That doesn't mean I only saw three periscopes in 18 years; I saw a lot more than that, but only three or so were initial detections. Whenever you get a sonar contact, sonar calls CIC and the bridge. The bridge watchstanders immediately look down the bearing of the contact. Sometimes, there's a periscope there, but these are cued not initial detections. If I had to attach an unclassified number to uncued detections, I’d say a ship had no better than a 10% chance, maybe less, of detecting a periscope that wasn’t way high out of the water and then only in daylight within 4000 yds. At night, or in low visibility, or high seas, forget it; zero percent.
Surface search radar, until the relatively recent advent of one and two second scan rates in systems like SPQ-9, was only a little better than visual. This was mostly because with six to ten second scan rates, everything as small as a periscope looks to the operator like sea clutter. And we didn’t get good at sea clutter rejection features until after the war. Plus radar sea return clutter is worst right where you’re wanting to look, within 6kyds of own ship.
So there I was last night in my S-40, west of the Ryukus, in February ’42. I was at periscope depth closing on a firing position, ahead standard, for a lone SHIRATSUYU Class DD who was off my port bow at 5000yds. He was doing 12kts on a course of about 340. The sun was setting behind his port quarter; time was like 1700. The thermal layer was at 150ft. He had been tracking right down his DRM (Direction of Relative Movement vector) and then at 5000 yds, he suddenly altered course right at me. At that range, I have no idea what he could have detected.
I'm running the U-boat missions add-on and TMO v1.5.
Along this line, do we know what the sonar/visual detection ranges are for the various settings in data/sim/cfg that you refer to in your FAQ?
Once again, I want to say, you’ve done a spectacular job with TMO. These are admittedly little things, and I thought you might enjoy the background. Bravo Zulu is the navy signal flag combination that means Well Done; in your case exceptionally so.
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