• Hi Guest! Forum rules have been updated. All users please read here.

Electric Submarines

merriman

David Douglass Merriman lll
Joined
Mar 18, 2013
Messages
450
Reaction score
544
Your informed question brings us back to the turn-of-the-century French all-electric submarine, GYMNOTE https://en.wikipedia.org/wiki/French_submarine_Gymnote_(Q1)

Seems that battery power density might be getting to the point where we once again can operate an all-electric submarine and only charge it at the pier when required. Only this time, for weeks of patrol, not hours.

David
DBF
 

Orionblamblam

CLEARANCE: Above Top Secret
Top Contributor
Senior Member
Joined
Apr 5, 2006
Messages
7,813
Reaction score
973
Website
www.aerospaceprojectsreview.com
One wonders if it might be practical to build underwater "charging stations." Connect said stations to "water turbines" or some other means of extracting electrical power from the flow of water. These would be both obvious and easy targets, but... maybe of some value. Preventing sabotage would be vital.

The subs themselves might be able to self-power in some circumstances... lock themselves to the ocean floor and deploy "water turbines" or some such. Probably not good enough to make the subs truly self sufficient, but maybe good enough for backup power.

How about this: the sub anchors somewhere with a high water velocity... near a river outlet or some such. Then it releases a parachute. The water pulls the parachute away from the sub, unreeling a kilometer or so of high strength cable. As the cable is unreeled, it spins a generator. When the cable reached the end, the parachute is reefed to reduce drag and pulled back in, rinse and repeat. Badguys appear during the chargin process, the cable is cut loose. All that's lost is a parachute and a cable, not the expensive charging gear.
 

MihoshiK

CLEARANCE: Confidential
Joined
Feb 9, 2007
Messages
172
Reaction score
89
Isn't this one of the ideas the Taiwanese are loooking at for their domestic submarines? Full electric?

Also, related, a larger image of the E-Moray, and the PDF of a follow-up of the original paper, which proposes a battery/fuel cell submarine:

 

Attachments

Last edited:

Grey Havoc

The path not taken.
Senior Member
Joined
Oct 9, 2009
Messages
11,704
Reaction score
1,830
One wonders if it might be practical to build underwater "charging stations." Connect said stations to "water turbines" or some other means of extracting electrical power from the flow of water. These would be both obvious and easy targets, but... maybe of some value. Preventing sabotage would be vital.

The subs themselves might be able to self-power in some circumstances... lock themselves to the ocean floor and deploy "water turbines" or some such. Probably not good enough to make the subs truly self sufficient, but maybe good enough for backup power.

How about this: the sub anchors somewhere with a high water velocity... near a river outlet or some such. Then it releases a parachute. The water pulls the parachute away from the sub, unreeling a kilometer or so of high strength cable. As the cable is unreeled, it spins a generator. When the cable reached the end, the parachute is reefed to reduce drag and pulled back in, rinse and repeat. Badguys appear during the chargin process, the cable is cut loose. All that's lost is a parachute and a cable, not the expensive charging gear.
A small atomic pile might be another alternative for onboard recharging, of the 'trickle' type.
 

stealthflanker

CLEARANCE: Top Secret
Joined
Feb 12, 2010
Messages
523
Reaction score
217
For a long range design, maybe in range 2300 Ton class and endurance of Nuclear submarine of 3 months and underwater speed of 10.7 Knot. One might need like 4-10 times of current power density of Li-Ion battery (about 250-260 Watt/pound) Without recharging and range of around the world.

That however still limit the Hotel load to about 200 KW which quarter is for life support (50 KW). The upgrade to electronics appears to be constrained by the battery capacity, more electronics = more power = more battery = more volume+weight needs to be allocated, the submarine will go bigger and may lose speed.

Still, despite being potentially attractive to smaller nation, i dont think diesel generator or other backup means of power generation can be dropped. Maybe it can use much smaller diesel but not entirely drop it.
 

Hobbes

CLEARANCE: Top Secret
Senior Member
Joined
May 9, 2008
Messages
827
Reaction score
191
The best batteries available today have an energy density about 10 times that of lead-acid batteries. If we take the 60 hours of underwater endurance (at 9 km/h) of a Type XXI as a starting point, you'd expect a current submarine using the best available batteries to be able to run for 25 days at slow speed. Double the speed and you'll divide radius of action by 4. Still marginal for most navies. Plus, Li-ion batteries are a major fire hazard.

Nevertheless, Japan already has a sub in operation (Ōryū) with Li-ion batteries replacing the AIP engine of the earlier boats in its class. It still carries diesel main propulsion though.
 

zen

CLEARANCE: Top Secret
Senior Member
Joined
Jul 15, 2007
Messages
1,931
Reaction score
644
Alternatively you can burn aluminium powder in water......

Though if you're into burning metal for power, iron powder is even more energetic.

I seem to recall something about this using nanoparticles of the metal
....
 

shin_getter

CLEARANCE: Confidential
Joined
Jun 1, 2019
Messages
111
Reaction score
62
One wonders if it might be practical to build underwater "charging stations." Connect said stations to "water turbines" or some other means of extracting electrical power from the flow of water.
I'd think recharging them via SSN would be the path of least resistance. Energy recovery from water takes too long and too much surface area.

With that kind operating concept, one can also wonder if a SSN could simply refuel fuel cell subs directly with liquid oxygen and hydrogen.
 

Hobbes

CLEARANCE: Top Secret
Senior Member
Joined
May 9, 2008
Messages
827
Reaction score
191
Swapping out the diesels for a nuclear plant seems to me to defeat the purpose of removing the diesels (i.e. to reduce complexity).
 

Grey Havoc

The path not taken.
Senior Member
Joined
Oct 9, 2009
Messages
11,704
Reaction score
1,830
Swapping out the diesels for a nuclear plant seems to me to defeat the purpose of removing the diesels (i.e. to reduce complexity).
An atomic pile wouldn't be the same as a full scale nuclear plant.
 

TomS

CLEARANCE: Top Secret
Senior Member
Joined
Apr 16, 2008
Messages
4,047
Reaction score
1,024
Swapping out the diesels for a nuclear plant seems to me to defeat the purpose of removing the diesels (i.e. to reduce complexity).
An atomic pile wouldn't be the same as a full scale nuclear plant.
What do you think a "pile" is then? It's a reactor.

That said, low-power reactor plus batteries is a form of air-independant propulsion that has been considered, usually annotated as SSn.
 

Hobbes

CLEARANCE: Top Secret
Senior Member
Joined
May 9, 2008
Messages
827
Reaction score
191
Depends on what you mean by 'atomic pile'.

An RTG would be simple, but an RTG large enough to drive a sub would be 100x larger than the RTGs we use today.

The reactor on the NR-1 was about the size we're talking about (100 kW), and that was a steam plant, with much of the complexity of a large reactor, just scaled down to a smaller package. Control rods, water and steam, fission products, radiation all present and complicated.
 

Foo Fighter

I came, I saw, I drank some tea (and had a bun).
Joined
Jul 19, 2016
Messages
1,458
Reaction score
460
A small nuclear pile would seem to be much less complex than a fully integrated power source similar to the units intended for battlefield deployment in larger hq areas. Would it be enough at the size needed to be fitted into the smaller sub's?
 

stealthflanker

CLEARANCE: Top Secret
Joined
Feb 12, 2010
Messages
523
Reaction score
217
Well what's that "pile" for first ? If we take it for following purpose e.g :

1.To charge battery underwater
2.To handle hotel load (Modern Diesel Electric Submarine can have about 200 KW of Hotel load, not including propulsion).

We can perhaps use value of 250 KW (some 350 Hp). Then we can compare it to typical power density of nuclear reactor. PWR is about 38 Kg/Hp (thus 13 Metric Tonne) for the entire plant, Liquid Metal Reactor is 25 Kg/Hp (8.9 Metric tonne) and Nuclear gas turbine 21 Kg/Hp (7.5 Metric tonne). Clearly the Nuclear Gas Turbine offers the lowest weight and therefore lower amount of volume to be accommodated in the submarine. However technology is rather immature for this despite repeatedly being proposed since 1960's.
 

sferrin

CLEARANCE: Above Top Secret
Senior Member
Joined
Jun 3, 2011
Messages
13,266
Reaction score
1,292
That's a lot of 18650s :D
 

Orionblamblam

CLEARANCE: Above Top Secret
Top Contributor
Senior Member
Joined
Apr 5, 2006
Messages
7,813
Reaction score
973
Website
www.aerospaceprojectsreview.com
Depends on what you mean by 'atomic pile'.

An RTG would be simple, but an RTG large enough to drive a sub would be 100x larger than the RTGs we use today.
.
Putting 100 rtgs in a sub would not seem to be a major problem given how small and simple they are. Probably run better than space rtgs since shedding heat is a whole lot easier in water than vacuum.
 

Hobbes

CLEARANCE: Top Secret
Senior Member
Joined
May 9, 2008
Messages
827
Reaction score
191
The cost might be a problem though. Current Pu-238 RTGs cost in the region of $30M each (for a few hundred W) because Pu-238 is difficult to make. You could use different materials (a shorter half life than 88 years wouldn't be a problem for a sub), but the nice thing about Pu-238 is that its entire decay chain is alpha particles, which means you only need minimal shielding.
 

Orionblamblam

CLEARANCE: Above Top Secret
Top Contributor
Senior Member
Joined
Apr 5, 2006
Messages
7,813
Reaction score
973
Website
www.aerospaceprojectsreview.com
The cost might be a problem though. Current Pu-238 RTGs cost in the region of $30M each (for a few hundred W) because Pu-238 is difficult to make.
Solution: work to produce Pu-238 in industrial quantities. Lots of benefits from doing so, using various processes... not only do you get to scrape the old pits out of your antiquated nukes and replace them with shiny new ones, you also get breeder reactors and enough Pu-238 to put RTGs into series production. One Pu-238 production method uses thorium reactors, which are worth doing on their own. And now you can fill the skies and the surfaces of worlds with hundreds and thousands of probes while also emplying a bagrillion shiny new nuclear engineers and scientists. You know, the kind of people who might actually make *fusion* work. And you get to toodle around the ocean for years at a time in itty bitty coastal subs that don;t emit any of that eeeeevvvviiiilllll carbon dioxide and aren't filled to overflowing with explodey lithium batteries.
 

Hobbes

CLEARANCE: Top Secret
Senior Member
Joined
May 9, 2008
Messages
827
Reaction score
191
You need ~10 MW of peak power with several hours of endurance at that level, so your RTG-equipped sub still needs a pretty big battery.
 
Top