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This related to, but not the same as, the mechanism by which modern torpedoes kill warships. Historically torpedoes used to hit the sides of ships, punching bi

This related to, but not the same as, the mechanism by which modern torpedoes kill warships. Historically torpedoes used to hit the sides of ships, punching big holes. The response by ship builders was to build empty “torpedo bulges” on the sides of ships to trigger the torpedo early, preventing structural damage. Modern torpedoes instead detonate under the ship. The explosion creates a massive bubble (most explosives being nothing more than a solid that’s itching to turn into a hot cloud of nitrogen). This bubble ends up under the ship, resulting in a ship that’s supported at the ends and not the middle. It turns out modern ships aren’t strong enough to support their own weight in this way, and the ship breaks in two. Obviously this lacks the grinding mechanism described here, but the similarity is in the application of a huge amount of force in the middle of a ship to break it.

sandworm101 6y ago
>> huge amount of force in the middle of a ship to break it. But that isn't what they are doing. This isn't cracking the ship into halves. This is very slowly grinding a hole through the structure. Look to the edges of the cut line and you will see the failure mode of the metal is very different. No sharp/jagged fractures, more round peeling off of metal. It is the difference between using an axe and using a saw.
- ashtonkem 6y ago
  It’s almost as if I put a disclaimer at the top of my post about how these two concepts were related, but not the same....
  - gist 6y ago
    I found what you said interesting (my other comment) and noted if you had said 'this reminds me of' probably others would not have jumped on you for the phrasing. (I thought it was fine and I learned something I hadn't known or thought of.)
throwaway0a5e 6y ago
This is a great example of a generalization gone well beyond the end of its usefulness. This has no relation to a torpedo at all except that the localized mechanical force exceeds what the material can handle. But that's how every, cutting bending shearing, swaging, grinding, etc, etc operation works.
- NikolaeVarius 6y ago
  Hah. "They both break things by applying force. Amazing coincidence"
  - tim333 6y ago
    Both breaking ships though.
    - meowface 6y ago
      And by applying upward force to a localized point beneath the ships. I actually found the comparison fairly helpful.
- Spivak 6y ago
  I think it's more that "hey you might assume that ships are these big strong things that you can't just cut through but that's a misconception; they're actually weak enough they can't even support their own weight -- a fact that was exploited by torpedo designers."
  - Accujack 6y ago
    It's also not true for some ships, depending on exactly what you're talking about. It isn't just being forced to support its own weight by a bubble that sinks ships... it's the force applied in the direction it's applied by the explosion of the torpedo. Most hulls aren't designed to handle a sudden non uniform upward moving force in their middle accompanied by a shock wave.
- Accujack 6y ago
wedn3sday 6y ago
Other people here are shitting on your comment, but I appreciate your random torpedo facts!
- treis 6y ago
  Unfortunately, that is wrong as well. Ships generally can support their own weight if only supported at the ends. Because waves exist a ship can find itself with the stern on one crest and the bow on the next with little or nothing supporting the middle. The under keel explosion works better because: (1) The weight of the ship acts against the explosion increasing the initial stress (2) The gas bubble created can vent straight up on a side explosion. Under the keel means it has to go through/around the ship increasing the stress. (3) Since the explosion lifts the ship you're going to get significant additional damage when it crashes back down into the water. (4) Like (2) as the gas bubble disperses water rushes back into the vacuum. All of this water coming back in will collide in the middle resulting in a geyser going straight up into the ship.
  - tim333 6y ago
    I was thinking the support it at the ends and it will break explanation is lacking. Thinking about it is you detonate an explosive under a boat it's going to create a shock wave that will hit the boat like a hammer and probably do a fair bit of damage to the hull before maybe the support at the ends thing happens.

sandworm101 6y ago

>> huge amount of force in the middle of a ship to break it. But that isn't what they are doing. This isn't cracking the ship into halves. This is very slowly grinding a hole through the structure. Look to the edges of the cut line and you will see the failure mode of the metal is very different. No sharp/jagged fractures, more round peeling off of metal. It is the difference between using an axe and using a saw.

ashtonkem 6y ago
It’s almost as if I put a disclaimer at the top of my post about how these two concepts were related, but not the same....
- gist 6y ago
  I found what you said interesting (my other comment) and noted if you had said 'this reminds me of' probably others would not have jumped on you for the phrasing. (I thought it was fine and I learned something I hadn't known or thought of.)

throwaway0a5e 6y ago

This is a great example of a generalization gone well beyond the end of its usefulness. This has no relation to a torpedo at all except that the localized mechanical force exceeds what the material can handle. But that's how every, cutting bending shearing, swaging, grinding, etc, etc operation works.

NikolaeVarius 6y ago
Hah. "They both break things by applying force. Amazing coincidence"
- tim333 6y ago
  Both breaking ships though.
  - meowface 6y ago
    And by applying upward force to a localized point beneath the ships. I actually found the comparison fairly helpful.
Spivak 6y ago
I think it's more that "hey you might assume that ships are these big strong things that you can't just cut through but that's a misconception; they're actually weak enough they can't even support their own weight -- a fact that was exploited by torpedo designers."
- Accujack 6y ago
  It's also not true for some ships, depending on exactly what you're talking about. It isn't just being forced to support its own weight by a bubble that sinks ships... it's the force applied in the direction it's applied by the explosion of the torpedo. Most hulls aren't designed to handle a sudden non uniform upward moving force in their middle accompanied by a shock wave.
Accujack 6y ago

wedn3sday 6y ago

Other people here are shitting on your comment, but I appreciate your random torpedo facts!

treis 6y ago
Unfortunately, that is wrong as well. Ships generally can support their own weight if only supported at the ends. Because waves exist a ship can find itself with the stern on one crest and the bow on the next with little or nothing supporting the middle. The under keel explosion works better because: (1) The weight of the ship acts against the explosion increasing the initial stress (2) The gas bubble created can vent straight up on a side explosion. Under the keel means it has to go through/around the ship increasing the stress. (3) Since the explosion lifts the ship you're going to get significant additional damage when it crashes back down into the water. (4) Like (2) as the gas bubble disperses water rushes back into the vacuum. All of this water coming back in will collide in the middle resulting in a geyser going straight up into the ship.
- tim333 6y ago
  I was thinking the support it at the ends and it will break explanation is lacking. Thinking about it is you detonate an explosive under a boat it's going to create a shock wave that will hit the boat like a hammer and probably do a fair bit of damage to the hull before maybe the support at the ends thing happens.