Magnesium Torpedo?

[richardphat]

Hello all, just wondering people say if magnesium is ignited and plunged into water, it would make a nice explosion. So how do you think it could be real if the germany have used magnesium torpedo?
Or they could have used Rubidium or Cesium?~?~?

[the.terrabyte.pirate]

Kinda dangerous to store it in a ship that's designed to go under water. I've never heard of a magnesium torpedo. I guess the risks would have outweighed any benefits... and I think that explosives detonate faster than magnesium's reaction to water.

Smarter people than me will have a better answer.

[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).

[siber]

The whole 'raison d'etre' for torpedoes is that water is a very effective absorber of thermal energy. An explosion is effectively cushioned by the water if the detonation occurs at a distance. This is why depth charges needed to be quite close to a sub to cause damage, the Dambusters raid needed to place the bouncing bombs right next to the dam, and why torpedoes need to explode either in contact with the side of a ship or immediately below it.

However, if the explosion IS in contact with the target, the damage is magnified as MORE explosive energy is directed into the target rather than the water...

As mentioned above, magnesium simply reacts with water without actually exploding. Therefore the release of energy is too slow to cause damage, but its energetic enough to cause a fire...

[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.