Contact detonation
When a torpedo with a contact fuze strikes the side of the target hull, the resulting explosion creates a bubble of expanding gas, the walls of which move faster than the
speed of sound in water, thus creating a
shock wave. The side of the bubble which is against the hull rips away the external plating creating a large breach. The bubble then collapses in on itself, forcing a high-speed stream of water into the breach which can destroy
bulkheads and machinery in its path.
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Proximity detonation
A torpedo fitted with a proximity fuze can be detonated directly under the
keel of a target ship. The explosion creates a gas bubble which may damage the keel or underside plating of the target. However, the most destructive part of the explosion is the upthrust of the gas bubble, which will bodily lift the hull in the water. The structure of the hull is designed to resist downward rather than upward pressure, causing severe strain in this phase of the explosion. When the gas bubble collapses, the hull will tend to fall into the void in the water, creating a sagging effect. Finally, the weakened hull will be hit by the uprush of water caused by the collapsing gas bubble, causing structural failure. On vessels up to the size of a modern
frigate, this can result in the ship breaking in two and sinking. This effect is likely to prove less catastrophic on a much larger hull, for instance, that of an
aircraft carrier.
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Damage
The damage that may be caused by a torpedo depends on the "
shock factor value", a combination of the initial strength of the explosion and the distance between the target and the detonation. When taken about ship hull plating, the term "hull shock factor" (HSF) is used, while keel damage is termed "keel shock factor" (KSF). If the explosion is directly underneath the keel, then HSF is equal to KSF, but explosions that are not directly underneath the ship will have a lower value of KSF.
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