Magnesium Torpedo?

[richardphat]

Originally Posted by Tombow

Magnesium burning underwater is rubbish. The reaction goes the following way:

Mg+2H20->Mg(OH)2+H2.

The reaction generates a great amount of heat and hydrogen. If a magnesium chunk is trown into water, the reaction heat is enough to ignite the hydrogen released provided there is contact with air - for a fire, an oxidizer is needed (in this case air oxygen). Underwater, there is no oxygen, so no fire. Inside an U-boot there is oxygen, so magnesium coming in contact with water can start a formidable fire.

As for military application, magnesium charges might be useful for fooling a heat-seeking torpedoes (if any of that kind exist).

How fish can survive without oxygen?!?!?!?(No offense)
Or do you mean fire cannot ignite and then no explosion??!?!?!? They can still use black powder it can burn without O2, or they can compress a bit of O2 inside the torpedo. Its very dangerous i know, i always thought the army will use any dangerous way to destroy something?

[patonb]

Also, the amount of heat input would be huge to actually ignite the magnesium of the size required.

[Sag75]

Hi, the oxygen is soluble in water, so fishes can survive into! The amount of oxygen solubilized is proportional to water temperature (higher temp->lower O2).
Anyway, in this medium oxygen is just mixed so isn't in a properly gaseous form to ignite an explosion..

[richardphat]

Originally Posted by Sag75

Hi, the oxygen is soluble in water, so fishes can survive into! The amount of oxygen solubilized is proportional to water temperature (higher temp->lower O2).
Anyway, in this medium oxygen is just mixed so isn't in a properly gaseous form to ignite an explosion..

Ah !! thx for the info!

[Cohaagen]

Richardphat - I take it you've just had a chemistry lesson? Because that's exactly what I thought of the first time I saw an alkali metal/water reaction many years ago.

As has been said, if you want a rapid oxidising reaction underwater usually you have to provide your own oxygen, such as in an oxy/acetylene torch. The only underwater application for magnesium I can recall, outside of sub/torpedo batteries, was in the old XCOM: TFTD game where they powered the dart gun ammo!

High explosives are actually very safe when stored correctly. They need an enormous shock to detonate - dropping on the floor just won't do. Even when set alight, they'll just burn like a block of hexamine instead of exploding. Something like lithium, on the other hand, is so unstable you need to store it in mineral oil to prevent it from reacting with the moisture in the air - not great for underwater use.