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Originally Posted by Subject
You do not need speed to dive to 180 meters. Maintaining depth do require constant monitoring and a lot of work, but that's why your boat is full of men 
Please don't spread myths. |
What myths? Lots of web sites by ex-submariners talk about the fact that true neutral buoyancy is impossible to acheive in a submarine. Practically speaking, the machinery, no matter how masterfully manned and handled, is not capable of such refined control of ballast and trim.
I've done a number of dives in small, 3-man deep diving submersibles. With state of the art, solid-state electronic controlled trim and ballast pumps, it was never possible to acheive and maintain true neutral buoyancy for more then brief periods of time. The Alvin pilots are some of the best trained submersible operators you'll find anywhere in the world, but no amount of artful control inputs from them could acheive precise depth maintenance for anything more then a few minutes without the use of the thrusters. And this in a vessel that only displaced a few tons, not thousands of tons.
The environment is the issue, and the environement is not stable, so you are in effect chasing a constantly moving target. For a submarine, at war, and with finite power reserves, that chase is costly - in terms of power, a ridiculous strain on the crew who must ultra-micro-manage a maze of buoyancy controls, and it makes noise running pumps and such.
As mentioned, much better off just slipping along at 1 knot or so, and let the dive planes do what they are intended for - depth and trim control.
A quote from a US Naval Officer and an engineer who served on the USS Loggerhead (SS-374, a Balao class boat) in WWII:
Quote:
Lt. HARRISON W. SIGWORTH
Modern United States Submarines
In Engineering and Science Monthly (California Institute of Technology), Volume 9:8, August 1946
...<snipped the first portion of article>
...
SUBMERGED OPERATION
The achievement of neutral buoyancy is a practical
impossibility. It can be approached by pumping
water out of the trimming tanks or flooding in; but
true neutral buoyancy in which the boat will stay anywhere
it is placed below the surface without sinking
or broaching is impossible. Depth can be maintained
within a foot for hours at a time, however, by propelling
the boat through the water and using the
diving planes. These are horizontal, tiltable, planing
surfaces olaced at the bow and stern to control dewth
and ang-l e of the boat.
... <article continues>
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the whole paper is
here