# What Happens When a Submarine Hits Crush Depth? **URL:** \ **Category:** Factual Questions\ **Created:** [February 24, 2010, 6:49am UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245 "2010-02-24T06:49:04Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![Fir\_na\_tine](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Fir\_na\_tine](https://boards.straightdope.com/u/Fir_na_tine)\ **Post date:** [August 16, 2016, 7:34pm UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/21 "2016-08-16T19:34:34Z")
> [@Snnipe\_70E](#): > > WWII fleet boats max designed depth was 400 feet. Keth O’Kane on the Tang went deeper. On trials he took the boat deeper until he blew a gasket in a flange. Brought the Tang back up, repaired the flange installed stronger bolts. Went deeper the next time until another leak developed, had that repaired and strenghtened. He kept it up until he could take the Tang down to 600 feet with no leaks. > > He used going to 600 feet to escape depth charging because the Japanese knew the max operating depth of a US fleet boat was 400 feet. I an not absolutely sure but I believe he learned this trick from Mush Morton. All I can say is that crew had balls, enormously big balls! ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [October 3, 2016, 8:22pm UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/22 "2016-10-03T20:22:32Z")
> [@Rick](#): > > Based on what I have read in several books once you get a couple of hundred feet down you don’t feel any surface wave action regardless of what is going up upstairs. > Maybe **Robby** can comment. Just saw this post… Anyway, this is a true statement, more or less. Once we submerged, we generally never felt any wave action. However…there was this one time that we were out in the North Atlantic with this huge storm going on above us, and the sonar operators were telling us that based on the noise they were hearing on the surface, the predicted sea state was 9+. (The [sea state](https://en.wikipedia.org/wiki/Sea_state) scale only goes up to 9.) Anyway, we were due to go to periscope depth for communications, so the CO decided to go up slowly to see if would be possible or not. At 400 feet deep, we didn’t really feel anything. At 250 feet, the boat started rolling, and by 150 feet, we were doing some pretty dramatic rolls that were getting progressively worse. At that point, the CO decided to bail on going to periscope depth and that we would try again after the storm had passed. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [October 3, 2016, 8:24pm UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/23 "2016-10-03T20:24:13Z")
> [@Snnipe\_70E](#): > > WWII fleet boats max designed depth was 400 feet. Keth O’Kane on the Tang went deeper. On trials he took the boat deeper until he blew a gasket in a flange. Brought the Tang back up, repaired the flange installed stronger bolts. Went deeper the next time until another leak developed, had that repaired and strenghtened. He kept it up until he could take the Tang down to 600 feet with no leaks. > > He used going to 600 feet to escape depth charging because the Japanese knew the max operating depth of a US fleet boat was 400 feet. I an not absolutely sure but I believe he learned this trick from Mush Morton. > [@Fir\_na\_tine](#): > > All I can say is that crew had balls, enormously big balls! I don’t doubt that the CO had balls. The crew, on the other hand, probably had ulcers. 😉 ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 3, 2016, 10:47pm UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/24 "2016-10-03T22:47:04Z")
> [@Sigene](#): > > I read"The Thresher Disaster" many years ago and distinctly remember the description was an implosion followed by an explosion as the diesel fuel on board detonated under the pressure. I’m not sure if this is true and would like to confirm if that is feasible or correct. I am aware that it was nuclear powered, but I remember the book stating they had diesel fuel for some reason I doubt the diesel could detonate, because it would have to have some sort of oxidizer mixed with it. The air in the sub couldn’t mix with the diesel fast enough to create an explosion. The explosives in any torpedoes could detonate though. It’s a lot easier to get gasoline to explode, because it can vaporize, mix with air, and then form an explosive gas. Diesel is a lot heavier and won’t vaporize and so it can’t mix thoroughly with air, and so won’t explode. Burn, sure, but not explode. The classic way to get diesel to explode is to pour it over ammonium nitrate. But even there the real explosive comes from the NH4NO3. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [October 4, 2016, 4:37am UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/25 "2016-10-04T04:37:32Z")
> [@Xema](#): > > Agreed - I doubt if in most cases it’s as much as a second between the heating and the quenching. The air doesn’t compress unless/until tons of water are rushing in to take (most of) its former place. > I doubt the hull crumples comprehensively. The instant it deforms enough to rupture somewhere, water rushes in and rapidly cancels the crushing force. > [@Snnipe\_70E](#): > > WWII fleet boats max designed depth was 400 feet. Keth O’Kane on the Tang went deeper. On trials he took the boat deeper until he blew a gasket in a flange. Brought the Tang back up, repaired the flange installed stronger bolts. Went deeper the next time until another leak developed, had that repaired and strenghtened. He kept it up until he could take the Tang down to 600 feet with no leaks. > > He used going to 600 feet to escape depth charging because the Japanese knew the max operating depth of a US fleet boat was 400 feet. I an not absolutely sure but I believe he learned this trick from Mush Morton. This would be my guess - the sub is not a one-hoss shay ( [Poem: The Deacon's Masterpiece, or, the Wonderful One-hoss Shay: A Logical Story](http://holyjoe.org/poetry/holmes1.htm) ) Most likely one point or other will fail first- a hatch, a seam, a port or flange where something goes through the pressure hull. Then the water rushes in and compresses everything, so the damage is limited as the pressure equalizes. You may have catastrophic chemical reactions once the oxygen partial pressure reaches flash point for whatever combustible materials are inside the hull, but I suspect that compared to external pressure, the force of any “explosion” will be muted unless there are interesting explosives on board and not submerged, so the compression process sets them off. In a diesel engine, the fuel is deliberately sprayed in a fine mist into the cylinder. Unless the compression process creates a mist, a major explosion is unlikely in my inexpert opinion. ---
**Author:** ![SCAdian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scadian/32/3292_2.png) [@SCAdian](https://boards.straightdope.com/u/SCAdian)\ **Post date:** [October 5, 2016, 1:41am UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/26 "2016-10-05T01:41:18Z")
> [@robby](#): > > Anyway, this is a true statement, more or less. Once we submerged, we generally never felt any wave action. > > However…there was this one time that we were out in the North Atlantic with this huge storm going on above us, and the sonar operators were telling us that based on the noise they were hearing on the surface, the predicted sea state was 9+. (The [sea state](https://en.wikipedia.org/wiki/Sea_state) scale only goes up to 9.) Anyway, we were due to go to periscope depth for communications, so the CO decided to go up slowly to see if would be possible or not. > > At 400 feet deep, we didn’t really feel anything. At 250 feet, the boat started rolling, and by 150 feet, we were doing some pretty dramatic rolls that were getting progressively worse. At that point, the CO decided to bail on going to periscope depth and that we would try again after the storm had passed. Happiness, as they say, is 400 feet in a state six sea. 🙂 ---
**Author:** ![normin](https://avatars.discourse-cdn.com/v4/letter/n/35a633/32.png) [@normin](https://boards.straightdope.com/u/normin)\ **Post date:** [October 27, 2016, 9:26pm UTC](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245/27 "2016-10-27T21:26:27Z")
> [@md2000](#): > > This would be my guess - the sub is not a one-hoss shay ( [Poem: The Deacon's Masterpiece, or, the Wonderful One-hoss Shay: A Logical Story](http://holyjoe.org/poetry/holmes1.htm) ) > > Most likely one point or other will fail first- a hatch, a seam, a port or flange where something goes through the pressure hull. Then the water rushes in and compresses everything, so the damage is limited as the pressure equalizes. You may have catastrophic chemical reactions once the oxygen partial pressure reaches flash point for whatever combustible materials are inside the hull, but I suspect that compared to external pressure, the force of any “explosion” will be muted unless there are interesting explosives on board and not submerged, so the compression process sets them off. > > In a diesel engine, the fuel is deliberately sprayed in a fine mist into the cylinder. Unless the compression process creates a mist, a major explosion is unlikely in my inexpert opinion. The British did a submerged crush test on a captured German submarine after World War II. I don’t know what depth they achieved, but failure occurred at the conning tower hatch. The hatch itself was found in the aft torpedo room. It had taken every hatch or bulkhead in between out on its passage aft, so, yes, failure would be catastrophic. The weakest points are always attachment points for something, or where a smooth continuous hull shape is broken by an irregularity such as a hatchway opening or a conning tower. [Previous page](https://boards.straightdope.com/t/what-happens-when-a-submarine-hits-crush-depth/530245.md?page=1)