Modern electric heavyweight torpedoes

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There are a couple things that modern electric heavyweight torpedoes can do that other torpedo types cannot do, or not nearly as well. Western navies usually don't have a mix of heavyweight torpedo types; they use either one or another design, and but two designs when they transition from an older generation to a new type. This may be far from ideal, as I will show by pointing out the potential versatility of modern electric heavyweight torpedoes.

First, a description:
A modern heavyweight torpedo with electric propulsion has or can have

• a giant battery capacity relative to other torpedo categories (depends on torpedo length),
• an electric motor capable of accelerating the torpedo to higher speed than any ship, but not as high speed as some other torpedo engines,
• a fibre-optic cable that connects the torpedo with the launch platform (submarine) with a high data transmission rate (two way),
• a passive/active sonar (including the ability to sense active sonars and incoming hard kill torpedoes),
• wakehoming terminal approach mode with the necessary sensor,
• a fuse that detonates the torpedo below the target ship and
• processing capacity to identify ships by their acoustic profiles and choose promising target approaches including retargeting after falling for a decoy without fusing.

an example of a modern electric torpedo;
other examples are the Indian Varunastra and the Italian Black Shark

There's little published info on how exactly modern torpedoes would be employed other than most simple patterns, so I'll simply write about some ways that could be done with this combination of attributes.

1. short distance sprint attack (guided or unguided)
2. normal wide-guided torpedo attack; medium speed cruise on intercept course, user chooses target based on torpedo's sonar data and torpedo initiates terminal attack sprint
3. long range self-deployment to mission area, sinks to ground, becomes mine (long life due to large battery capacity), engages detected target in very short range sprint
4. entire salvo of torpedoes deploys at slow speed to a location in front of a predictable convoy (or into a narrow strait), uses just enough propulsion to avoid sinking too low, torpedoes act as mobile mines and initiate engagement when convoy comes close enough
5. multiple torpedoes launched at slow or medium speed, sonars and accurate navigation enable a accurate-enough triangulation of acoustic signatures even though the submarine's sonar couldn't determine the range to the target in passive mode on its own (at least not quickly and reliably).
6. torpedo used as mobile decoy, mimicking submarine behaviour and to some degree its acoustic signature. It could reproduce picked-up active sonar waves if its own sonar can cover the same frequency band. The fake contact could even be behind the torpedo as long as there's but one active sonar looking for it (and the torpedo's echo is too small to be picked up).
   
7. hard kill defence against incoming torpedo (that's inefficient with a heavyweight torpedo, but feasible)
8. torpedo launched in one direction, possibly left there for a while (as the sub rests at sea bottom as well) and finally tasked to simulate a threat from its axis in order to lure targets into the sub's no-escape kill zone as part of their evasive action
9. HWT as mobile and spaced active decoy, mimicking active sonar signals (if its own sonar can cover that frequency band) and thus faking a moving submarine

The important advantages of the electric HWT are in its endurance. This is visible in the mobile mine applications, including the torpedo salvo-in-ambush scenario (#4) and the self-deploying mobile mine scenario (#3).

A navy that limits itself to a torpedo such as Mk48ADCAP or Spearfish misses out on many of the above-listed scenarios in favour of a higher sprint speed.

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BTW, I still suppose that submarines could be well-served with a SSG approach; a dozen vertical launch silos for modern anti-ship missiles could enable a submarine to quickly engage distant audible contacts without reliable range estimate and without needing to replace torpedoes in the torpedo tubes (which would be a problem in a surprise contact with a hostile submarine). The launch could be from such long distances and the missiles could fly such a pre-programmed path that the attack wouldn't give the location of the sub away.

That in turn begs the question why one should go to such lengths (submarine operation, sub-launched anti-ship missiles) at all, since land-based air power is really good at deploying anti-ship missiles as well.

The answer is in my opinion that submarines are still platforms that make the most sense for underdog navies and navies that insist on attacking where their surface fleet and air power cannot routinely go. Submarines can go on missions even when and where hostile forces dominate the sky and the surface.

I see but one real justification for non-SSBN submarines in European service; the employment as aggressors in training of ASW units. The ship-killing and reconnaissance functions could be accomplished by much more versatile air power.

related

/2013/08/extra-long-range-torpedoes.html

/2013/02/serious-naval-mines-could-be-very-very.html

S O

defence_and_freedom@gmx.de

P.S.: I know there are hordes of SSN fans who read too many biased books, but I'm not going to convince any of those people about how unnecessary and redundant SSNs are anyway.

edit 2019:
There's also the theoretical option of letting a torpedo engage an ASW helicopter that's using a dipping sonar. It could triangulate the stationary dipping sonar (only minehunting dipping sonars are towed AFAIK), sprint towards it, jump out of the water and engage well within lethal radius to the helicopter IF the dipping sonar was deployed for a long-enough time (which is a truly big IF). So that's a 10th, hypothetical, employment option.

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