A few questions for sub experts

Edwin · 10-16-08, 11:41 PM

I have been doing a bit of reading but I haven’t been able to find the answers to these. Maybe some bright sailor can enlighten me

1) Compressed air usage in modern SSNs – I understand how subs use MBTs, trim tanks, hydroplanes, etc. to change depth. However, I’m not clear on how much compressed air is used for this in a modern SSN. My understanding is that pumps do most of the work. More specifically, I'd like to know the following:
a) Does an SSN regularly use any compressed air for changing depth? Specifically at very low speeds (“zero” knots). If yes, could this be a significant source of noise?
b) Could an SSN run out of compressed air by doing lots of depth changes?
c) Can the supply of compressed air be replenished without surfacing? After all, oxygen can be replenished through the electrolysis of water, so I assume that it should be possible to acquire compressed air too provided the equipment is there…

2) Limber holes are used in free flood areas. There are a particularly great number of them on double hulled subs due to the large free flood areas. Since these may generate noise, modern Russian SSNs use limber hole covers that close when the sub dives. But:
a) Do the covers still have to be opened if the sub changes depth or enters a region where the density of water is different?
b) Just thought of this now: Assuming the covers are closed and the appropriate equipment is there (like pumps) could these areas act like some sort of ballast tanks? If yes, why isn't this done?

solitear · 10-21-08, 09:54 AM

I think I can answer these.(submarine qualified navy vet E5)

1) a sub is either positively buoyant and floats..ballast tanks full of air..

or the tanks are full of water and the sub is negatively (nuetrally? its been awhile) buoyant and tends to sink....

depth is adjusted via dive planes. \A)no B)no c) yes

2) I don't know anything about subs with limber hole covers.......

10-16-08, 11:41 PM	#1
Edwin Nub Join Date: May 2007 Posts: 4 Downloads: 164 Uploads: 0	A few questions for sub experts I have been doing a bit of reading but I haven’t been able to find the answers to these. Maybe some bright sailor can enlighten me 1) Compressed air usage in modern SSNs – I understand how subs use MBTs, trim tanks, hydroplanes, etc. to change depth. However, I’m not clear on how much compressed air is used for this in a modern SSN. My understanding is that pumps do most of the work. More specifically, I'd like to know the following: a) Does an SSN regularly use any compressed air for changing depth? Specifically at very low speeds (“zero” knots). If yes, could this be a significant source of noise? b) Could an SSN run out of compressed air by doing lots of depth changes? c) Can the supply of compressed air be replenished without surfacing? After all, oxygen can be replenished through the electrolysis of water, so I assume that it should be possible to acquire compressed air too provided the equipment is there… 2) Limber holes are used in free flood areas. There are a particularly great number of them on double hulled subs due to the large free flood areas. Since these may generate noise, modern Russian SSNs use limber hole covers that close when the sub dives. But: a) Do the covers still have to be opened if the sub changes depth or enters a region where the density of water is different? b) Just thought of this now: Assuming the covers are closed and the appropriate equipment is there (like pumps) could these areas act like some sort of ballast tanks? If yes, why isn't this done?

10-21-08, 09:54 AM	#2
solitear Swabbie Join Date: Oct 2008 Posts: 6 Downloads: 0 Uploads: 0	I think I can answer these.(submarine qualified navy vet E5) 1) a sub is either positively buoyant and floats..ballast tanks full of air.. or the tanks are full of water and the sub is negatively (nuetrally? its been awhile) buoyant and tends to sink.... depth is adjusted via dive planes. \A)no B)no c) yes 2) I don't know anything about subs with limber hole covers.......