# Submarines **URL:** \ **Category:** Factual Questions\ **Created:** [June 7, 2014, 5:07am UTC](https://boards.straightdope.com/t/submarines/690253 "2014-06-07T05:07:38Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Raguleader](https://avatars.discourse-cdn.com/v4/letter/r/258eb7/32.png) [@Raguleader](https://boards.straightdope.com/u/Raguleader)\ **Post date:** [June 8, 2014, 3:43am UTC](https://boards.straightdope.com/t/submarines/690253/21 "2014-06-08T03:43:43Z")
> [@robby](#): > > You mean **sonar** , **Raguleader** , which is sound-based. Radar does not work underwater. > > While active sonar (the one with the pings) does give away a sub’s presence, modern submarines use passive sonar extensively. Indeed, it’s the main piece of detection equipment. I meant radar, but was under the impression that it worked underwater, just not very well. ISTR seeing a documentary about looking for sunken wreckage that talked about how they’d use Sonar to find a probable bit of wreckage, then use radar to verify. As I recall it, the sonar had a longer range (more useful for searching an area) and the radar had higher definition but shorter range (so kind of useless for searching, but better for taking a closer look at something in particular). I could be misremembering though, this would have been on TV many years ago. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [June 8, 2014, 4:07am UTC](https://boards.straightdope.com/t/submarines/690253/22 "2014-06-08T04:07:06Z")
When I was taking flight training 20 years ago, we were told to never use white light at night - all the lighted kneepads, even the baby Maglites, had red filters "to preserve “night vision”. I always wondered by what miracle could I look at a white-light dashboard under white street lighting and not immediately run tinto the first semi shining its white lights in my face. I later heard that the white-light-destroys-night-vision theory was myth. Anyone with more experience _in training_ care to share what they are currently preaching as gospel. I could go to Sporty’s. but I’m lazy and in pain. ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [June 8, 2014, 4:58am UTC](https://boards.straightdope.com/t/submarines/690253/23 "2014-06-08T04:58:36Z")
> [@usedtobe](#): > > I always wondered by what miracle could I look at a white-light dashboard under white street lighting and not immediately run tinto the first semi shining its white lights in my face. There’s FAR more light on a street or highway than a dark night at sea. ---
**Author:** ![Raguleader](https://avatars.discourse-cdn.com/v4/letter/r/258eb7/32.png) [@Raguleader](https://boards.straightdope.com/u/Raguleader)\ **Post date:** [June 8, 2014, 4:58am UTC](https://boards.straightdope.com/t/submarines/690253/24 "2014-06-08T04:58:41Z")
Having worked in darkrooms as part of my photography habit, I can tell you, you can see an impressive amount of stuff in relative darkness after you’ve been in it for a long enough time. But that’s measured in tens of minutes, not in seconds. The reason you don’t notice a lack of night vision when driving your car at night is because you are constantly getting headlights shined in your face, thus you’re used to not being able to see anything without shining a pair of high intensity white lights at them. ---
**Author:** ![PurpleClogs](https://avatars.discourse-cdn.com/v4/letter/p/f04885/32.png) [@PurpleClogs](https://boards.straightdope.com/u/PurpleClogs)\ **Post date:** [June 8, 2014, 5:45am UTC](https://boards.straightdope.com/t/submarines/690253/25 "2014-06-08T05:45:50Z")
> [@campp](#): > > As pointed out above, yes. You have to use what space you have available. The movie [Das Boot](http://www.imdb.com/title/tt0082096/) made a clear point of the storage situation. That’s the movie I just watched. It’s very good, long, but worth it. Subtitled on Netflix. ---
**Author:** ![Ornery\_Bob](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@Ornery\_Bob](https://boards.straightdope.com/u/Ornery_Bob)\ **Post date:** [June 8, 2014, 5:55am UTC](https://boards.straightdope.com/t/submarines/690253/26 "2014-06-08T05:55:03Z")
**Modern SONAR is THAT good.** My cousin was on a so-called fast attack sub out of Point Loma (San Diego) and he said that when starting a deployment, they would go just past the edge of the continental shelf and then drop below it and sit for hours just listening until they had identified every source they could hear, which, he said, included ships just leaving Honolulu harbor. That’s over 2000 miles. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 8, 2014, 12:45pm UTC](https://boards.straightdope.com/t/submarines/690253/27 "2014-06-08T12:45:30Z")
> [@usedtobe](#): > > When I was taking flight training 20 years ago, we were told to never use white light at night - all the lighted kneepads, even the baby Maglites, had red filters "to preserve “night vision”. > I always wondered by what miracle could I look at a white-light dashboard under white street lighting and not immediately run tinto the first semi shining its white lights in my face. > I later heard that the white-light-destroys-night-vision theory was myth. > > Anyone with more experience _in training_ care to share what they are currently preaching as gospel. > > I could go to Sporty’s. but I’m lazy and in pain. The aviation biz has pretty much abandoned the “red light for night vision” theory. It was gospel before the 1980s, but isn’t much believed in now. I suspect as other have pointed out, that we really can’t run cockpits as blacked out as would be necessary for the red light to have much effect. Also with the advent of computerized color-coded displays & backlit panels, floodlighting is mostly a thing of the past at least for primary illumination. For civil aviation we’re not trying to retain the level of night vision that rises to seeing unlit ships on unlit open ocean. And for military aviation we now have effective NVGs and NVG-compatible cockpits. All in all, nobody I’m aware of still builds aircraft with red cockpit lighting, nor do many pros carry red flashlights. ---
**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:** [June 8, 2014, 1:06pm UTC](https://boards.straightdope.com/t/submarines/690253/28 "2014-06-08T13:06:15Z")
> [@robby](#): > > Another ex-submariner here… > > …However, you also have seals, like the propeller shaft seals that are not 100%. Seawater does leak in. > [@Lukeinva](#): > > :eek: > > :smack: Yes, indeed. The amount of seawater pouring in around the main propeller shaft seals was truly alarming the first time I saw it, particularly at deep depths. Note that the seals are trying to keep out the surrounding sea pressure with a 2-ft diameter main shaft rotating within the seals. Anyway, the water ends up in the bilge, which is subsequently pumped into holding tanks and oil/water separators, and the non-oily water is pumped to sea. > [@Raguleader](#): > > I meant radar, but was under the impression that it worked underwater, just not very well. ISTR seeing a documentary about looking for sunken wreckage that talked about how they’d use Sonar to find a probable bit of wreckage, then use radar to verify. As I recall it, the sonar had a longer range (more useful for searching an area) and the radar had higher definition but shorter range (so kind of useless for searching, but better for taking a closer look at something in particular). > > I could be misremembering though, this would have been on TV many years ago. I’m not aware of any radar technology that will work underwater. For radar to work the frequency has to be relatively high, and high-frequency radio waves are readily absorbed by water. There are high-frequency active sonars that are often used for underwater searches of wreckage, including so-called [side-scan sonar](http://en.wikipedia.org/wiki/Side-scan_sonar). [Previous page](https://boards.straightdope.com/t/submarines/690253.md?page=1)