Re: [PSUBS-MAILIST] Test and questions

[Gregc02@ibm.net]

>    A friend told me that U.S. Navy subs use carbon dioxide in
> their ballast systems.  I am skeptical.  Is this true?  The only
> reasons I could think of were maybe for quieting or
> firefighting, and even then, wouldn't it be impractical and more
> expensive to use than just the good old regular air?  This is a
> question for you ex-bubbleheads out there.


As an ex bubblehead, the only systems I've ever seen (or heard of) in US Submarines are plain 
old air. On WWII fleet boats the high pressure air system was a nominal 3,000 psi, reduced to 
225 psi for ship service air used for tools and blowing sanitary tanks and engine starting. Ballast 
tank blow was 3,000 psi air reduced through expansion to 600 psi nominal and introduced to the 
tanks by manual valves on the high pressure air manifold. There were six banks of high pressure 
air bottles outside the pressure hull in the ballast tanks.
The nukes of my time (1960s) used much the same systems except that they used remote, 
electrically actuated valves. 

>    Another one recently posed to me is how much air pressure you
> need to have available to blow your ballast tanks.  I assumed it
> was equal to or greater than the ambient pressure of the water
> at the depth you are working at.  Yes?  No?  

True, although the more blow pressure you have the faster you can get the water out of the 
tanks. Fleet boats used the high pressure air for initial blow (usually from periscope depth) and 
then when on the surface and with the main induction valve and/or the conning tower hatch open, 
start up the low pressure blower to finish up the blowing of water from the tanks without using up 
high pressure air. I believe that at least some of the WWII German boats used engine exhaust to 
finish the blow instead of a low pressure blower.

Hope this helps,

Greg Cotton

ex-USS Torsk (SS-423)