2009/05/15

Semi-submersibles

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The German submarines of WW2 were not what people expected them to be (and what many still think they were).
As someone has put it, they were no real submarines, Unterseeboote (undersea boat) yet, but mere Tauchboote (diving boats).

Even the introduction of snorkels didn't change that much, as submarines at that time were still dependent on fresh air from above surface till the first nuclear-powered submarine.
The Germans of WW2 turned this insufficiency of submarines of their time into a strength. Their tactic against convoys was not an underwater attack, but a surface torpedo attack - only the withdrawal was under water.


This worked quite well at night when detection was possible, but the Allies spent enormous efforts on solving the problem and forced the Germans to develop some of the first SSK - high-speed submarines that were much more able to fight under water.
The Japanese actually did the same with the a bit less sophisticated Sen-Taka and Sen-Taka Sho, btw.

The key to the German type VII submarines' success in early WW2 design laid on the surface, though: They were able to sneak past the few escorts at nighttime thanks to a small bridge/superstructures silhouette. The detection of such a small object was very tough in 1939-1942, radars were still in their infancy.

Back to the present...

Latin American drug smugglers use many techniques to smuggle their freight, and one of their latest success stories are semi-submersible boats that move at the surface, but with a minimal signature above water. Just like Type VII. More here.

Their success is a harsh kick of reality into the balls of those who trust sensors and modern technology.


The boats should be easy to detect, but were in fact not - even today a semi-submersible could slip past the Coast Guard.

Coast Guard and USN already fear that the Latin American drug smugglers could learn how to make real submarines that would be invisible to radar.
So we spent decades of the Cold War preparing for all-out warfare at sea and a couple of improvised submarines in relatively confined areas would be a huge challenge?



Anyway - the relevant part of this all is the low observable and low freeboard of such designs. It's risky, but could pay off in certain niche applications.

The minimal freeboard offers a tiny radar signature and target area to sea skimmer missiles. This design could possibly be used to build relatively missile-resistant boats.
The low signature could also help to enhance their overall survivability against radar-based threats.

Later more about that...

Sven Ortmann
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1 comment:

  1. Interesting analysis. I've wondered recently if a modern Tauchboote wouldn't solve some of the littoral warfare problems we see today. Operating any surface vessel within visual range of a defended shore is a dangerous proposition (as the Hanit found out).

    And yet true SSKs suffer from their painfully slow transit speed and lack of utility in peacetime (compared to a surface ship).

    I wonder if one could buld a Tauchboote that could keep up with a task force on the surface, and provide surfaced capability (perhaps even a help hangar and pad). But when the situation dictates, it could dive to avoid surface threats.

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