Question for Sid...

[DuckofTindalos]

Do you know if the IJN ever developed and deployed a torpedo tube-launched mine?

[el cid again]

Yes. This is the reason that their minelaying submarines (modified copies of a WWI German sub minelayer) were not produced after the first set. [USN also had a dedicated minelayer - but she never did lay mines - although they probably were technically superior: her gear was stripped out so she could carry almost a company of troops and she did many special operations of supply and raiding.] The Japanese adopted the practice, long before WWII, of laying most of their mines via tube from any available submarine - although unlike us they did also use their dedicated sub minelayers with their specialized mines. In fact, only one type of Japanese sub laid mine was NOT suitable for TT use - and that was the kind for the minelayers after tubes. They could ALSO lay mines via their forward (regular torpedo) tubes - so their minelaying mission capability actually grew after the introduction of TT mines. If you want specific data, I can provide it, or you can look in Naval Weapons of the Second World War (John Campbell) - who tries to list them all for every nation.

[DuckofTindalos]

Please provide specifics. I can't find a single reference to a non-KRS submarine laying torpedo tube-launched mines, except for the I-6 laying German TMC mines off Australia.

[el cid again]

The Type 1 (which inspired a major family of post war USN mines) was a swimmer from I type submarines - they swim into an enemy harbor without requiring the submarine to enter it. It used 88 kg (165 lb) of Type 88 explosive which was 66% ammonium perchlorate, 16% ferro-silicon, 12% wood pulp, 6% oil.

The Type 2 was a copy of the US Mark 10 submarine mine, but it used Japanese explosives: 130 kg (287 lb) of Type 97 which was 60% TNT, 40% hexanitrodiphenylamine. Later a "Type B" variant of it used 16% aluminum and 24% hex.

The Type 3 Model 1 was a copy of a German submarine laid mine - the TMC. It was a magnetic influence mine.

The Type 3 Model 2 was a copy of a German submarine laid mine - but it used acoustic influence for detonation.

Both of these used 890 kg (1962 lb) of Type 97 explosive.

[DuckofTindalos]

Okay. Do you know how widely they were used?

As far as I could find, the Type 3 Model 1 was an air-dropped mine with only about 180lbs of explosive. That's at least what NavWeaps.com says, and it's source is supposedly "Naval Weapons of World War II" by Campbell.

[el cid again]

Well - the types I just listed should have entered service in 1941, 1942 and 1943 respectively - because that is what Type numbers signify in this era. It is an accident they correlate to our calendar - they actually correlate to Japanese dating systems with the same final digit and the leading digits surpressed. I have not found immediately a listing for an earlier mine, but there should be one - because in the world of submarine design it was not regarded as necessary to build more minelayers. The minelayers used the Type 88 - as you probably know.

None of the Type 1, 2 or 3 were made in great numbers. OTH, submarines cannot carry great numbers of mines - compared to surface minelayers that carry hundreds - or aircraft - which can fly many times.

[spence]

(Coincidentally) Would not Type 3 indicate first design approval or maybe production in 1943?

Oh Cid beat me to the "OK"

[DuckofTindalos]

Yeah. That's just about the only thing, mine-wise, that the stock game has right with regards to the IJN subs. Assigning the Type 88 to torpedo tubes is certainly incorrect.

[DuckofTindalos]

The Germans did their torpedo tube-launched mines well; they designed their TMA/B/C mines so that multiple examples could fit in a standard tube and be launched at once. The TMA and TMC (which was a development of the TMA) could fit two in a tube, and the TMB three in a tube.