Re: Submarine Ballast Tanks {revisited}

[Coast Guard Kiteman <exfloridians@ecsu.campus.mci.net>]

At 07:14 AM 6/27/1998 -0700, you wrote:

>Hi Kiteman,
>>        For what it's worth, I just watched part of a show on TLC (The
>>Learning Channel}
>>called NUCLEAR SUB: SEAWOLF.  I say "part" because I forgot to start the VCR
>>when the show came on.   [Oh pooh.]  This show mainly profiled the new USN
>>submarine
>>"Seawolf".


>Almost makes cable worth having. 


        If it wasn't for TDC, TLC, and Babylon 5 on TNT, [plus the wife being
addicted to NASCAR, NBA, and WNBA], I'd dump cable altogether.


>>        Anyway, they mentioned something I asked here some time back.  They
>>showed
>>that earlier subs used ballast tanks that ran along the sides of the hull.


>Saddle tanks do stick out from the sides. Which creates a larger cross
>sectional area which translates into drag. The only advantage to saddle tanks
>is that their bouyancy  off to each side aids in surface roll stability. In
>other words they are great for submarines which spend most of their time on
>the surface.


        Which sounds like the 'dream submarine' I've got somewhere in the
back of my head.


>>Now however,
>>subs use tanks at the front and rear (or thereabouts), which allows for
>>faster diving
>>and/or surfacing.


>Submarines that use the tear drop shape, like the American nukes, are much
>more stream lined. As a result the ballast tanks are put just about the only
>place the pressure hull isn't, in front and in back. 
>
>Being more steamed lined the nukes do go faster for a given amount of power.
>However, since the axis of the ballast tanks are centered on the lognituginal
>axis of the pressure hull the roll stability on the surface is sluggish at
>best.


        As I've read elsewhere.  Though I didn't know not having saddle tanks
contributed to this.  I thought it was only the teardrop shape.


>As for "diving and/or surfacing", nukes spend most of the time at sea
>submerged , so they only need to dive or surface once or twice per cruiz. So
>they don't need to dive, or submerge, very quickly. I understand it take 4 to
>8 minutes to submerge. Part of the reason is that the holes in the bottom of
>the ballast tanks are relatively small to  reduce the flow noise at these
>holes at higher speeds.
>
>An old diesel-electric boat with saddle tanks spends most of it's life on the
>surface. When it had to get submerged it had to do it now. Often in under 30
>seconds.
>
>I guess the surfacing speed was simular for both types of ballast tanks.


        Were the old diesel boats ever equipped for 'emergency blow', or is that
just something on nuke boats since the 60's?