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Japan's Silent Submarines Extend Range With Lithium-Ion Batteries (nikkei.com)
AmiMoJo shares a report from Nikkei Asian Review: Japan's first submarine powered by lithium-ion batteries was launched on Thursday. The [Soryu-class diesel-electric] submarine can reach speeds of roughly 20 knots and displaces 2,950 tons. It will be delivered to the Japan Maritime Self-Defense Force in March 2020. Batteries are recharged by the energy generated by Oryu's diesel engines. The vessel switches to batteries during operations and actual combat in order to silence the engines and become harder to detect. The lithium-ion batteries radically extend the sub's range and time it can spend underwater.
... out on the Big Pond.
Aviation Anti-Submarine Warfare Technician 2nd class.
The other side of the story is using hydrophones (waterproof microphones) to listen to the deep.
Every major country has these permanent stations anchored out across the oceans.
An audio spectrum analyzer sweeps the apparently random noise with tones from near zero up to the khz.
Obviously, when noise from the sea is the same frequency as the artificial pure tone, they are added together.
Rinse, repeat.
The results are charted with frequency on the X axis and amplitude on the Y.
A computer alerts when it sees a straight line, created over time.
That's the tone and sea noise agreeing when they coincide with the sounds of reefers (ice boxes), generators, prop cavitation, screw bearings, engine noises, and miscellaneous unwanted fingerprints.
We could tell you the fucking captain's name by the signature.
Aircraft drop sonobouys to do the same.
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Then there's this:
Submarines, to date, have a lot of fucking metal that distorts the Earth's magnetic field locally.
Permanent or airborne magnetometers can pick up these small anomalies.
Sunken ships have long been logged and they don't move.
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Then, there are active sonar devices, permanent or airborne (tethered from helicopters) that map the surroundings and alarm on novel or moving objects.
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The submarine/anti-submarine balance of technology is similar to the battle of virus/antivirus one.
This latest improvement by the Japanese may or may not be better than existing or future state of the art detection.
It little behooves the best of us to comment on the rest of us.
WW II era submarines were not diesel-electric. They were electric underwater, diesel on the surface. A real diesel-electric uses a diesel to drive a generator that in turn drives electric motors. Obviously, this isn't possible when submerged.
When all you have is a hammer, every problem starts to look like a thumb.
I could have written "submerged below snorkel depth" but I assumed an intelligent reader. More to the point, I erred in claiming that WW II submarines were not actually diesel-electric. They actually were.
When all you have is a hammer, every problem starts to look like a thumb.
Kamikaze tactics had nothing to do with submarines.
Yes they did: Kaiten suicide subs.
Nuclear also has it's issues. A diesel electric sub is much quieter, and therefore harder to detect, than a nuclear as long as the diesel electric is running in electric mode. The trade-off is that when running the diesel it's much, much, louder, and the all electric range tends to be limited. Nuclear allows longer range and relative quiet, but not as quiet as electric.
This is interesting because it extends that electric range, and therefore extends the advantage over nuclear in short term engagements.
Noise isn't necessarily the problem with nuclear reactors, it's the heat. They dump a bunch of heat into the water, which can be picked up by satellites. They have to go *deep* to evade detection this way, which limits where they can go. You won't be able to tell *exactly* where the sub is, but you get the idea that one is in the area, and it's general direction.
My Other Computer Is A Data General Nova III.