# Vacuum hulls for quiet navy submarines **URL:** \ **Category:** Factual Questions\ **Created:** [March 1, 2021, 7:50pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052 "2021-03-01T19:50:25Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [March 2, 2021, 5:28pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/61 "2021-03-02T17:28:44Z")
> [@Acierocolotl](#): > > am I suggesting connecting the vacuum hull to the pressure hull with bungie cords? > > YES, YES I AM. LOTS OF BUNGIE CORDS. Just about everything that makes noise is already effectively attached to the hull with bungee cords. We know a lot more about how to make sound isolation mounts than we do how to make 100 m incompressible, maglev, thermos bottles. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [March 2, 2021, 5:32pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/62 "2021-03-02T17:32:43Z")
No kidding. I got less radiation as a submariner than I do going about my daily life now. A lot less. Amine and CO2 might have been a bit excessive… ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [March 2, 2021, 5:38pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/63 "2021-03-02T17:38:01Z")
I don’t understand the point of complicated double hulls that can be punctured losing a vacuum or gas and leaving a space to flood with water eliminating a huge amount of buoyancy. Why not just use acoustic foam or other material lining the inner hull? And can’t there be technology like noise blocking headphones to change the sounds emanating from a sub so they seem more like an unidentifiable noise? I understand the problem is that it’s still a noise that can be located, and if it doesn’t sound like a whale or school of fish then it’s not really any help, but maybe that can be managed also. And how about little noise generating torpedoes that are like chaff, in this case to clog up a sonar readings instead of radar? ---
**Author:** ![Acierocolotl](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/acierocolotl/32/6241_2.png) [@Acierocolotl](https://boards.straightdope.com/u/Acierocolotl)\ **Post date:** [March 2, 2021, 5:43pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/64 "2021-03-02T17:43:42Z")
> [@abcdefghij](#): > > Just about everything that makes noise is already effectively attached to the hull with bungee cords. But of course, it’s not a maglev vacuum thermos, it’s a bungee thermos. Huge difference. But in fear of being serious for a moment, I didn’t know you were shock-mounting noisy machinery. I’ll admit I hadn’t thought about it, and it makes perfect sense. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 2, 2021, 5:50pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/65 "2021-03-02T17:50:11Z")
> [@TriPolar](#): > > And can’t there be technology like noise blocking headphones to change the sounds emanating from a sub so they seem more like an unidentifiable noise? I understand the problem is that it’s still a noise that can be located, and if it doesn’t sound like a whale or school of fish then it’s not really any help, but maybe that can be managed also. There is a common misperception that active noise cancelling headphones can neutralize all sound, which leads to complaints about how the don’t block conversations or other sharp, low frequency noises. In fact, headphones with active noise cancelling sample the ambient acoustic environment and cancel mid- and high-frequency pseudo-“white” noise (like the humming of an engine or aeroacoustic vibration of an airframe flying through the air) but do little if anything for conversational noise or mechanical sounds. > [@TriPolar](#): > > And how about little noise generating torpedoes that are like chaff, in this case to clog up a sonar readings instead of radar? Launching a torpedo is one of the immediately recognizable sounds a submarine can make because of the high pressure air to push the fish out into the water. Acoustic sonar arrays are highly directional, so sound made in one direction does not really affect sounds coming from another direction; you’d literally have to disrupt the acoustic environment across a broad frequency spectrum in a wide area to “clog up” the sonar picture. One tactic if another submarine fires upon you is to launch a torpedo back at them, hammering them with active pinging and forcing them to cut the control wires so they can turn away, which I’m sure is unnerving but even that won’t really prevent being able to track other submarines. Stranger ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [March 2, 2021, 5:52pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/66 "2021-03-02T17:52:37Z")
> [@TriPolar](#): > > Why not just use acoustic foam or other material lining the inner hull? They [already have that](https://en.m.wikipedia.org/wiki/Anechoic_tile) (although it goes on the outside). As for active noise cancellation, I guess you could do that, but submariners and submarine designers are already pretty good at not making any noise in the first place. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [March 2, 2021, 6:00pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/67 "2021-03-02T18:00:56Z")
But… but, nuclear energy is EEVIL! 😉 ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [March 2, 2021, 6:03pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/68 "2021-03-02T18:03:29Z")
> [@Acierocolotl](#): > > But of course, it’s not a maglev vacuum thermos, it’s a bungee thermos. Huge difference. I apologize. I didn’t mean to malign you with magnets. I don’t even believe in “magnets”. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [March 2, 2021, 7:52pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/69 "2021-03-02T19:52:25Z")
> [@gnoitall](#): > > I vaguely remember reading someplace a few years ago that this was the next major field of acoustic processing technology in sonar: not detecting a point source of non-ambient sound (like plant noise or screw turns) but a point attenuation, a “hole in the water”. If you can sweep for ambient noise, you can catch an unnatural and sharply-delimited reduction in that ambient background and localise it. There’s your _Ohio_-class hiding. “It’s quiet. Too quiet.” ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [March 2, 2021, 8:01pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/70 "2021-03-02T20:01:28Z")
> [@Deeg](#): > > I think the most promising submarine detection is electromagnetic radiation and magnetic fields but water is a good insulator and it’s hard to see them coming up with much. In WW III the subs will be the last survivors. My first job out of college was working on a power supply for the Trident fire control system. There was a lot of concern regarding conducted EMI getting into the boat’s hull, which would theoretically allow detection of the state of the fire control system at some distance. The EMI filter was huge, about 20% of the volume of the entire power supply. ---
**Author:** ![EdelweissPirate](https://avatars.discourse-cdn.com/v4/letter/e/8491ac/32.png) [@EdelweissPirate](https://boards.straightdope.com/u/EdelweissPirate)\ **Post date:** [March 2, 2021, 8:20pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/71 "2021-03-02T20:20:44Z")
> [@Riemann](#): > > The calculation for an additional thickness of steel hull about 1/8 the thickness of the vacuum would still apply. Yes indeed. Plus, you’d need that additional thickness (and likely a bit more) for the pressure hull anyway. The vacuum will effectively pre-stress the outer hull in compression, requiring that it be a little thicker to create extra sectional modulus to prevent buckling at depth. In other words, if you want a vacuum-isolated-hull sub, the pressure hull will have to be significantly thicker to handle the extra stress, and that thickness is almost certainly enough to offset the extra buoyancy from the vacuum. A vacuum sub is impractical, but not because of the extra buoyancy. ———— On a separate point, even fairly stiff connections between the pressure hull and the inner hull could produce enough of an impedance mismatch to reduce some of the acoustic signature. But my understanding is that the impedance mismatches already in place (by design) mean that any acoustic improvement from a vacuum hull would get lost in the noise—but I yield to the expertise of the board’s submariners on that point. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 2, 2021, 8:45pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/72 "2021-03-02T20:45:30Z")
> [@Acierocolotl](#): > > But of course, it’s not a maglev vacuum thermos, it’s a bungee thermos. Huge difference. > > But in fear of being serious for a moment, I didn’t know you were shock-mounting noisy machinery. I’ll admit I hadn’t thought about it, and it makes perfect sense. You can’t shock mount the hatches, the periscope, the torpedo tubes, etc - those things have to penetrate both the outer and inner hulls, and they have to stay aligned. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 2, 2021, 9:00pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/73 "2021-03-02T21:00:06Z")
> [@Mangetout](#): > > You can’t shock mount the hatches, the periscope, the torpedo tubes, etc - those things have to penetrate both the outer and inner hulls, and they have to stay aligned. Most new design submarines use an [optronics mast](https://science.howstuffworks.com/photonic-mast.htm) that doesn’t require a pass-through for an optical tube. Hatches, torpedo and missile tubes, and of course the screw shaft(s) and other controls have mechanical passages between the pressure hull and the outer hull. Stranger ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 2, 2021, 9:01pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/74 "2021-03-02T21:01:56Z")
Sure, but does it need to protrude (I suppose _in_trude) into the main body of the sub when it is lowered? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 2, 2021, 9:06pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/75 "2021-03-02T21:06:24Z")
> [@Mangetout](#): > > Sure, but does it need to protrude (I suppose _in_ trude) into the main body of the sub when it is lowered? Read the linked HowStuffWorks article; the periscope well for the AN/BVS-1 photonics mast is entirely contained within the sail outside the pressure hull. Stranger ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 2, 2021, 9:07pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/76 "2021-03-02T21:07:06Z")
Fair enough. The point still stands for all the other stuff. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [March 2, 2021, 9:09pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/77 "2021-03-02T21:09:13Z")
> [@Mangetout](#): > > You can’t shock mount the hatches, the periscope, the torpedo tubes, etc - those things have to penetrate both the outer and inner hulls, and they have to stay aligned. Personnel hatches penetrate, but they’re not operated when submerged and they’re not hard-connected to noisy people and noisy machinery. Torpedo and missile hatches are noisy, but so are torpedoes and missiles. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 2, 2021, 9:11pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/78 "2021-03-02T21:11:17Z")
How about instead of vacuum, fill the gap with those noise-cancelling headphones? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 2, 2021, 9:12pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/79 "2021-03-02T21:12:31Z")
> [@abcdefghij](#): > > Personnel hatches penetrate, but they’re not operated when submerged and they’re not hard-connected to noisy people and noisy machinery. Isn’t that another way of saying the idea of a vacuum interhull is unnecessary? In a sub of this hypothetical design, the hatch opening would be a rigid, sound-transmitting link between the inner and outer hulls, if there’s no noise in the inner hull to be transmitted via such a link, then there’s no need for this vacuum idea. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 2, 2021, 9:36pm UTC](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052/80 "2021-03-02T21:36:37Z")
> [@LSLGuy](#): > > Oh no! not the vacuum blimp again. Last time I remember we went for pages and pages about vacuum blimps / balloons and the proponents just Would. Not. Get. It. Not the most recent one, but I think you mean this: > [@Why no vacuum or hydrogen based airships?](https://boards.straightdope.com/t/why-no-vacuum-or-hydrogen-based-airships/763811): > > I know that the Hindenburg clearly put a dent in people’s confidence in hydrogen’s usefulness in lighter than air travel, but that was a very long time ago, and there are still questions as to whether the hydrogen or the paint involved was responsible for that disaster. One would think that after th better part of a century, with new materials and technology that someone could engineer a way to use hydrogen safely in lighter than air travel. It weighs half of what helium does and is nowhere n… [Previous page](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052.md?page=3) [Next page](https://boards.straightdope.com/t/vacuum-hulls-for-quiet-navy-submarines/934052.md?page=5)