Gato / Balao Submarine "Can't" vs "Must" Surface on Dead Battery

[Silly Questions]

TL;DR Summary

What exactly happens when the battery dies?

I've read a lot about Gato / Balao / Tensch class submarines, the ones America used in WWII, and I can't seem to sort out the specific consequences of a dead battery. A lot of you are diesel experts, so maybe someone here knows?

Historical accounts are vague. Dead batteries are certainly a big problem obliging time on the surface recharging, but the consequences of the batteries dying while submerged is the ambiguous part. From the skipper's point-of-view it makes almost no difference: there's one solution to one problem, so indeed whether the batteries are dead or merely dying you do quite soon need to surface and recharge. But some accounts suggest that if the batteries die while underwater it's automatic death -- no "blowing the tanks" and rising to the surface staring worriedly into each others' flashlights on a dead battery. Dead battery = can't as in CANNOT surface AT ALL = dead boat.

If the battery dies while underwater, does that mean the submarine CANNOT surface or does it mean it must blow the tanks and surface, whatever the risk, because the crew isn't going to last long with dead batteries? What I've read seems to be interpretable both ways, and the fact that there's very little practical difference between the two is certainly what makes the accounts seem so vague.

There's an emergency generator for starting the engines without sufficient battery power, but that doesn't prove anything as the threshold for starting engines might be above a hypothetical threshold for surfacing -- if indeed some battery power is required to surface.

 

[Baluncore]

But some accounts suggest that if the batteries die while underwater it's automatic death -- no "blowing the tanks" and rising to the surface staring worriedly into each others' flashlights on a dead battery.

I think you will find there are two different buoyancy systems, and two modes of battery failure.

The first involves fine balance, with internal high pressure trim tanks at each end of the vessel. They are used to trim the buoyancy either side of zero, by pumping small volumes of water between the sea and the trim tanks. To reach the surface, only the trim tanks need to be pumped out. That can be done with very little electrical energy, maybe even by hand.

The second buoyancy system involves the huge external pannier or side tanks, always open below to the sea. Once at the surface they can be blown with low pressure air to displace the water, so raising the submarine deck above the sea surface, giving freeboard.

Physical damage to the batteries (by nearby depth charges) can be repaired by re-configuring the battery to isolate damaged cells. The trim tanks can then be pumped.

Water entry to the pressure hull that reaches the battery banks produces toxic gasses. Batteries do not go “completely flat”, but they can be damaged beyond repair. The chlorine gas produced may prevent access for repair.

Damage to the pressure hull, that allows too great a mass of water to enter, may make it impossible to surface using the trim tanks.

Damage to the side tanks (for example by gunfire) may allow air to escape, so the submarine lies 'in' the surface, usually leaning to one side, but not much above it.

 

[Rive]

Summary:: What exactly happens when the battery dies?

If the battery dies while underwater, does that mean the submarine CANNOT surface or does it mean it must blow the tanks and surface, whatever the risk, because the crew isn't going to last long with dead batteries?

As far as I know emergency blowing capability was already kind of 'must have' in all WWII submarines (I would not vouch for Japanese types, though...). If they went down with adequate supply of compressed air they could blow the main ballast tanks with only (manual) mechanical intervention.
Dead batteries are about the loss of depth control. With the natural instability of the depth control, unless they could 'sit down' somewhere they would be forced to blow at some point even if their air (CO2-removal) supply could hold on longer.

But to be honest I don't know much about the mentioned classes.

 

[Silly Questions]

So:

Dead battery = obliged to blow tanks due to loss of depth control, which would spell eventual doom. "Can't surface" is incorrect; "must surface" is correct.

Threshold of charge considered "not dead" = whatever is required to maintain depth control.

I'd love to hear your answer confirmed by someone with more direct knowledge, but your explanation does at least makes perfect sense.

 

[Baluncore]

I'd love to hear your answer confirmed by someone with more direct knowledge, but your explanation does at least makes perfect sense.

You cannot beat the original training manuals.

Compressed air was used to “blow” the main ballast tanks when near the surface and 600 psi pressure was available. 10 psi was used on the surface. Compressed air at several different pressures was delivered from the various stages of a four stage piston pump, driven by a 55 HP electric motor.

Buoyancy control was by transfer of water between internal trim tanks and the sea. That pump system was critical to reaching the surface. It was based on a six stage high pressure centrifugal pump, driven by a 10 to 25 HP electric motor. There was also a drain pump driven by a 10 HP electric motor.

The power needed for the water transfer necessary to surface was small when compared to the two 1370 HP, 2600 amp geared propulsion motors.

There were two separate main storage batteries. Each had 2 banks of 126 cells. Those were capable of driving the boat underwater and operating the pumps necessary to surface. If both those batteries were lost then there was no way to surface. Both would never be run flat by propulsion, it would require battle damage to cripple both batteries.
If the pressure hull was breached then the submarine could not surface anyway, due to lack of sufficient buoyancy to overcome the inflow of sea water.

You can now study the training manuals for those boats.
They are based on the Balao-class, USS Perch, SS313, from the end of WW2.
The Fleet Type Submarine, Navpers 16160 to 16169 manual series.
The series has now been digitised and can be found at;
https://maritime.org/doc/fleetsub/index.htm

 

[Silly Questions]

You cannot beat the original training manuals.
https://maritime.org/doc/fleetsub/index.htm

You, sir, are a legend!

I'm curious whether "can't drain the batteries flat with propulsion" means "can't" or "won't", but if propulsion becomes impossible below a certain charge threshold that question is moot: the crew aren't going to kill themselves trickling the last of their waning power into motors that won't turn.

The original training manuals. All questions answered. What a find!

 

[Rive]

Compressed air at several different pressures was delivered from the various stages of a four stage piston pump, driven by a 55 HP electric motor.

According to the linked manual, when submerged the source of air was the air banks (sum 560 cubic feet, at 1500-3000psi pressure). For blowing the MBTs the pressure was reduced to 600psi. No mention of pumps at all. Just valves.
600psi is ~ 400m depth (never went that deep, of course - not with ever coming up).

 

[Baluncore]

For blowing the MBTs the pressure was reduced to 600psi. No mention of pumps at all. Just valves.

Submarines usually creep up to the surface, then have a cautious look around before raising their profile. Buoyancy control will be done quietly using the pumped internal trim and ballast tanks. The internal tanks are not designed to be blown.

The problem with blowing the main external ballast tanks at depth is that the ascent will be uncontrolled. As the external hydrostatic pressure reduces toward the surface, the air in the external ballast tanks expands forcing out water, increasing the buoyancy further. The submarine will be deaf and blind during the ascent. Breaking the surface will be spectacular, with a possibility of collision, while the noise and the mass of bubbles will give away the position.

Blowing the external ballast tanks can be done in an emergency, for example if the pressure hull was breached, but then the external tanks will also likely be damaged and may not hold the air invested.

 

[Rive]

The problem with blowing the main external ballast tanks at depth is that the ascent will be uncontrolled.

Absolutely. A last ditch effort to save the crew when/if the batteries are down.

 

[berkeman]

Absolutely. A last ditch effort to save the crew when/if the batteries are down.

Interesting. Thanks for that.

An emergency main ballast tank blow is a procedure used aboard a submarine that forces high-pressure air into its main ballast tanks. The high-pressure air forces ballast water from the tanks, quickly lightning the ship so it can rapidly rise to the surface.

The partial failure of the emergency main ballast tank blow system, caused by icing of strainers in the air lines due to "the high volume of air moving past the strainers at such high velocity [which] would have caused them to cool rapidly," contributed to the loss of USS Thresher in 1963. That accident resulted in substantial redesign of submarine emergency blow systems by the United States Navy: "Part of this initiative was to end the practice of brazing smaller pipes, and to instead start welding and doing X-ray inspection of joints to verify their integrity. It also resulted in changes in designs of the system that blows out the ballast tanks, providing a capability to do so seven times faster than the system used in the USS THRESHER"[1]

 

[Silly Questions]

I read about the Thresher. Several systems failed in a cascade that caused the loss of the boat. The crew did everything right, but too many design and construction flaws doomed them anyway. What tragic loss of life.

One thing I could never find an explanation for is why the main coolant loop needed a special DC motor. Why not an AC motor for the main loop?

IIRC the propulsion failure went like this:
1. A weld breaks on a seawater pipe during the dive to test depth
2. Seawater pours onto the DC dynamo (which itself is driven by an AC motor)
3. The crew, following procedure, sets the planes for surfacing and propulsion to full
4. The main coolant motor, running on DC battery power, switches to high-speed mode, a setting required by and only by full-power propulsion
5. Insufficient power is available in the high-speed setting due to the inoperable dynamo
6. Detecting a main loop fault the computer scrams the reactor
7. Propulsion dies soon after as the heat exchanger rapidly cools

Would an AC motor have driven the main coolant loop at the pressure required for full propulsion? Why not an AC motor?

 

[Baluncore]

A last ditch effort to save the crew when/if the batteries are down.

Showing off how fast you could surface, if you needed to, cost nine lives.
https://en.wikipedia.org/wiki/List_...2000#Ehime_Maru_and_USS_Greeneville_collision