Originally Posted by Dr.Sid
Even with mile deep .. sub game is mostly 2D game. 1 mile away from enemy is WAY too close. And if you are 10 miles from enemy, 1 mile up or down wont do much difference. So from geometry point of view, there is no real sense.
Getting under the layer is important .. but layer is usually a lot shallower. And if it is deep, it's not so strong.
With mile of depth and so you could reach isothermal water, where lies the main speed of sound minimum and where strong sound channel is formed. That can be good for listening, but bad for your own stealth.
For preventing cavitation depth is good.
As with buoyancy .. you should not think that since the pressure is huge, the sub will be 'expelled' from water more. It is the case in air, but that's because air also changes density with pressure, while water for all practical purposes does not. On the other hand the submarine will be squeezed a bit at large depth .. which lowers it's volume, which actually lowers buoyancy. Sub trimmed neutral at periscope depth will want to sink near crush depth.
As for the blow .. HP air is stored in fixed volume pressure bottles. When they are full, the pressure is usually around 300 atmospheres. That is pressure at depth 3000 meters.
At 100m, the ratio of bottle pressure and water pressure is 300:10 or 30:1 .. and the tanks can be blown as long as there is at least 10 atmospheres, or 3% of air in the bottles.
At 1000m, the ratio of pressure is only 3:1, and you can blow air into the tanks only if there is at least 100 atm in the bottles, ie. at least 33%.
This difference in ratio means, that:
1) air will fill tanks a lot slower, even given volume at 1 atmosphere.
2) because of the outer pressure, the air will be compressed 10 times more, so for every cubic meter of air volume you have to pump 10 times more air in. So the speed of getting 'free buoyancy' can be 50 or more times slower near crash depth. There might not even be enough air to empty the tanks completely at crush depth. Air will expand during ascent, and any excess air will eventually leave the tanks through lower openings, but you want to leave the large depth ASAP. Because ..
3) With any leak, water will flow in a lot faster at large depth. Maybe not 10 times faster, speed of flooding is rather complex problem, but easily 5 times faster.
Also, as I mentioned, there is problem of controls jam. At periscope depth, if sub controls jam during 5 degree dive at 5 knots, you have relatively lots of time. At least you can blow fast to overcome dynamic forces. You might also be able to fix the problem.
Same things happens near crash depth at 20 knots while diving 20 degrees .. before you know you are beyond crash depth.
So depth does also affect safe speed, and maneuvers.
PS. Oh yes .. my poor subs. Well it's not officially dead at all. I'm doing minor stuff on it. But it's more like to keep it up to date with my computer. I don't have much time for it at the moment. There also seem to be little concern really. As the progress is scarce, I moved the project on facebook, it's easy to find, so I suggest you join it there, to be in touch. There is some progress on active sonar, which proved a bit more complicated then I thought. If I find some time and will, in two weeks of work I could do new release I guess.
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