Reading through this thread again, I notice the question, for example from Tom17, of how to compare the effects of hits by different torpedoes. One of the main issues is the comparison of Japanese Type 93 torpedoes with German, British and American torpedoes. My perhaps surprising take on this is that they may be roughly equivalent.
There is a thread which one can drop into the middle of at http://warships1discussionboards.yuku.c ... ce?page=10
which discusses particularly German torpedo warheads. http://www.navweaps.com/Weapons/WTGER_WWII.htm
has these made of “hexanite” but comments that the weight is very uncertain stating: “Warhead weight for these torpedoes confilicts in many references. I have seen numbers as low as 617 lbs. (280 kg) and as high as 948 lbs. (430 kg). It is possible that the lower numbers were for torpedoes issued early in the war and then heavier warheads were introduced during the war.”
The same site gives the explosive compositions of World War II Torpedoes as:
SW18: 50% TNT, 24% HND, 15% Aluminum
SW36: 67% TNT, 8% HND, 25% Aluminum
SW39: 45% TNT, 5% HND, 30% Amonium Nitrate, 20% Aluminum
SW39a: 50% TNT, 10% HND, 5% Amonium Nitrate, 35 % Aluminum
HND = Hexanitrodiphenylamine.
Thus we can be fairly confident that a German G7 warhead was between 280 kg and 430 kg and contained aluminium
Again according to Naval Weapons http://www.navweaps.com/Weapons/WTJAP_WWII.htm
Japanese Type 93 torpedoes contained 490 kg of Type 97 explosive, which was identical to German WW1 “hexanite” and was about 7% more powerful than TNT, until 1944 when larger charges entered service. The submarine launched Type 95 model 1 carried 405 kg of the Type 97 explosive but from 1944 the model 2 with a 550 kg warhead and shorter range entered service and that presumably sank Indianapolis.
Most American torpedoes that hit anything and exploded contained 600 lbs (air dropped) or 668 lbs (submarine launched) of Torpex, which is a mixture of 37-41% TNT, 41-45% RDX (cyclonite, cyclomethylene trinitramine) and 18% aluminum. Torpex is roughly 50% more powerful than TNT. USN destroyers seem to have used 801 lb TNT warheads until there were no more targets.
RN submarines changed from 722 lbs. (327 kg) of TNT to 805 lbs. (365 kg) of Torpex in 1943.
Thus the higher power of non-Japanese explosives would seem to compensate for their lower weight.