A sunken WWII-era Japanese 'mega sub' has been found near Hawaii

Illustration for article titled A sunken WWII-era Japanese mega sub has been found near Hawaii

Researchers diving off the coast of Hawaii have found a sunken 400-foot (122 meter) "Sen-Toku" class submarine. One of the largest pre-nuclear subs ever built, the "mega sub" was torpedoed by the U.S. shortly after the Second World War to prevent the Soviet Union from getting their hands on the super-advanced technology.

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Longer than a football field, and only one of three ever built, the I-400 disappeared from the radar (so to speak) in 1946. It has been missing ever since.

Illustration for article titled A sunken WWII-era Japanese mega sub has been found near Hawaii
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The sub has now been rediscovered off the southwest coast of O'ahu by researchers from the University of Hawaii and Manoa and a National Oceanic and Atmospheric Administration (NOAA) Maritime Heritage research team. The sub was resting in 2,300 feet of water.

The sub was scuttled by U.S. forces after the Soviet Union demanded the ship be returned to Japan. The divers say it was torpedoed, partially collapsed, and had sunk at a steep angle.

Illustration for article titled A sunken WWII-era Japanese mega sub has been found near Hawaii

The I-400 was one of the most advanced submarine of its time. Along with its sister ship, the I-401 (which was found off O'ahu in 2005), it could travel one and a half times around the world (37,500 miles) without refueling, and it could hold up to three folding-wing bombers (also known as float plane bombers) which could be launched just minutes after resurfacing. Each plane was capable of carrying a 1,800-pound (816-kilogram) bomb that could have potentially been dropped on the U.S. mainland. And in fact, as part of the Japanese master-plan to control the entire Pacific Ocean, the I-400 was to be used in an attack on the Panama Canal.

"The innovation of air strike capability from long-range submarines represented a tactical change in submarine doctrine," added James Delgado, the director of NOAA's Maritime Heritage program, in a statement. "The large I-400, with its extended range and ability to launch three M6A1 Seiran strike aircraft, was clearly an important step in the evolution of submarine design."

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In addition, the ship's giant watertight hangar was a step towards the ultimate development of ballistic missile launching capabilities for U.S. submarines at the dawn of the nuclear era.

One Sen-Toku class submarine remains missing.

The discovery was announced earlier this week after NOAA had reviewed its findings with the U.S. State Department and Japanese government officials.

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Related: Sunken Nazi sub found in Indonesia | Nearly intact Kittyhawk found in the Sahara.

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Images: NOAA/University of Hawaii at Manoa

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DISCUSSION

"The I-400 was the most advanced submarine of its time."

I am sorry, but thats a very big NO. Why is it, that the language on Io9 has been so thoroughly corrupted by superlatives in describing everything?! Do the writers think, articles such as this would not be worth reading if not making such assertions?

As others will undoubtedly point out, the German Type XXI and XXIII were in many regards much more advanced designs, most notably being true submarines instead of surface vessels diving for a very limited time and in a very limited area.

The I-400 was an impressive achievement of engineering and can claim to be the largest submarine of WW2, but it was also just a submersible really, a vehicle, that by far and large was meant to operate on the surface. In many aspects it was the opposite of innovation, making the most of established technology instead of introducing truly new concepts (very much like the largest battleship of all times, probably not a coincidence). It certainly did not contribute anything to submarine design, that was taken up after the war in designing new types. Delgado's assertion is blatantly wrong, unless he can point to a single submarine after WW2, that actually took up any of these features (most notably the airplanes), the watertight hangar was an interesting feature, but not a drastic innovation, as the older French Surcouf had exactly the same feature. Type XXI and XXIII are basically the grandfather of every modern diesel-electric submarine design, be it for battery capacity, hydrodynamic hull, lack of surface weaponry and emphasis on pure torpedo-warfare, an advanced combat management system, that could quickly calculate firing solutions, sophisticated automation, that enabled rapid ordinance reloading, and last but not least crew comforts, such as a shower, refrigerator, decent berthing etc. All these issues do not stack up well for the I-400 being innovative at anything really.

The US still sank it to prevent the Soviets from getting their hands on it, because they did so with everything they faced and which had unique qualities, whose potential use by the Soviet Union was hard to gauge. Nevertheless the Soviet Union, just as the rest of the Allies, gained much more insights from XXI, to the extent, that all their initial post-war designs were effectively based on that and a fair bit of other German kit, such as the Walter-engine (so dangerous to operate, that it was essentially a failure and rendered obsolete by nuclear power, but nevertheless at the time one way forward).