Modern Naval Submarine Discussion

[Erwin_Pommel]

Now this may seem like a dumb question, but has anyone ever looked at trying to recharge the batteries on a sub using human-powered means i.e. stationary bikes with a generator attached?

No, as it would be too consuming to do it when the sub can just have a piston system using the water its in to move it and work it. You'd also get shorter operation times as the crew would run out of food quicker due to a higher demand caused by the exercise done.

But it seems like the sort of thing that would be simple and easy to fit into an existing SSK design.

Simple and easy doesn't mean necessary nor efficient.

If your sub was the size of a small car, then, sure, you could probably do something with a bike, but such a sub would be useless as any benefits it has are counteracted by much better equipped and significantly more efficient drones and aerial vehicles or just bigger subs in general.

To sum up, a pedal bike power system would be a waste of space, time and effort.

 

[Bacle]

No, as it would be too consuming to do it when the sub can just have a piston system using the water its in to move it and work it. You'd also get shorter operation times as the crew would run out of food quicker due to a higher demand caused by the exercise done.


Simple and easy doesn't mean necessary nor efficient.

If your sub was the size of a small car, then, sure, you could probably do something with a bike, but such a sub would be useless as any benefits it has are counteracted by much better equipped and significantly more efficient drones and aerial vehicles or just bigger subs in general.

To sum up, a pedal bike power system would be a waste of space, time and effort.

I wasn't thinking of it as a main charging system, more as a supplement to allow SSKs to stay submerged longer.

 

[Erwin_Pommel]

I wasn't thinking of it as a main charging system, more as a supplement to allow SSKs to stay submerged longer.

Still the same problems and ones that can be supplemented with a water intake system with the sub's own momentum feeding it and ultimately creating the heat and friction needed for the power additions. Which is something that has been around since the Second World War iirc.

If you wanted a supplement, you'd be better off wiring a multi-battery system of where the batteries switch over periods of time and let one charge while another drains and then switch and so on. Would leave more space open and be more effective.

 

[Francis Urquhart]

That is unless you are the defending navy, supported by air force, ground based missile batteries and defensive minefields. That was the doctrine of Yugoslav navy, area denial with strikes of opportunity, using the geography to their advanage.

The problem is though that it cedes the initiative to the opposition and leaves the fleet open to attack when said opposition has all its pieces in play. Also, without long-range surveillance, it will be hard for the defending fleet to know when the attacks will come, from where and when. I've talked quite a bit with Swedish military people over this and they place a lot of faith in the same ideas you mention but the same problem holds in the Baltic. Once initiative has been ceded, its very hard to get back yet without it trying to conduct an effective defense is very hard. Swedish geography gave them an edge because the islands and fjords are so steep-edged that they make using stand-off missiles hard.

 

[Francis Urquhart]

Now this may seem like a dumb question, but has anyone ever looked at trying to recharge the batteries on a sub using human-powered means i.e. stationary bikes with a generator attached? I mean it wouldn't put out a lot of power, and I guess maybe there could be noise issues. But it seems like the sort of thing that would be simple and easy to fit into an existing SSK design.

It has been looked at (almost everything one can think of has been examined by somebody - one of the things that makes my job really fun) but the problem is that the amount of charge that can be generated that way will only be adequate to slow the aggregate discharge rate - in other words, put the entire crews on bicycles and the batteries will still be running down. By the way, some of the very old submarines had similar kinds of arrangements. The Hunley for example had her propeller driven by men turning cranks. Another issue is that all those men pedaling bicycles will generate noise (squeaks, rattles, whirring etc etc). The real thing though is that there just wouldn't be enough current generated. A typical submarine battery has 248 - 360 cells and there are usually two or three of them. A diesel takes four to eight hours to charge them so you can imagine how long a bicycle system would take.

Having said that, for midget and coastal submarines that don't have the crippling demand for electricity that the larger subs have, some form of manual generation might be practical. I'd have to ask though whether the set-up would be more efficient if drove the propeller directly rather than via the battery.

 

[Francis Urquhart]

If you wanted a supplement, you'd be better off wiring a multi-battery system of where the batteries switch over periods of time and let one charge while another drains and then switch and so on. Would leave more space open and be more effective.

That's more or less how a modern submarine battery works. Normally one has two or three (these days usually three) battery banks, one forward, one central, one aft and the control system switches between them so that the charge on all the cells remains roughly equal. That really is critical. Diesel-electric submarine drivers spend their lives with one eye glued firmly on their charge meters. That's why bubbleheads all go slightly mad.

By the way, for those who have You-tube, there's a very good series there called "Britain's Biggest Warship" about HMS Queen Elizabeth. Gives a very good look into what goes on behind the scenes in a modern warship.

 

[Bacle]

It has been looked at (almost everything one can think of has been examined by somebody - one of the things that makes my job really fun) but the problem is that the amount of charge that can be generated that way will only be adequate to slow the aggregate discharge rate - in other words, put the entire crews on bicycles and the batteries will still be running down. By the way, some of the very old submarines had similar kinds of arrangements. The Hunley for example had her propeller driven by men turning cranks. Another issue is that all those men pedaling bicycles will generate noise (squeaks, rattles, whirring etc etc). The real thing though is that there just wouldn't be enough current generated. A typical submarine battery has 248 - 360 cells and there are usually two or three of them. A diesel takes four to eight hours to charge them so you can imagine how long a bicycle system would take.

Having said that, for midget and coastal submarines that don't have the crippling demand for electricity that the larger subs have, some form of manual generation might be practical. I'd have to ask though whether the set-up would be more efficient if drove the propeller directly rather than via the battery.

I figured it wouldn't be enough to do more than a trickle charge per bike, and there would be noise concerns, but figured it was worth asking.

 

[Francis Urquhart]

I figured it wouldn't be enough to do more than a trickle charge per bike, and there would be noise concerns, but figured it was worth asking.

It's a good question and I can see some applications (midgets especially) where it might be useful. Might not be an exercise bike per se but a foot-pedal design that could be operated while the midget was on the bottom would be worth looking at. A midget wouldn't have the space for anything elaborate like a diesel or fuel cells. One could see an arrangement where its primary role is to exercise the crew and the trickle-charge take-off would be a bonus.

 

[Marduk]

I figured it wouldn't be enough to do more than a trickle charge per bike, and there would be noise concerns, but figured it was worth asking.

To me it seems like a very inefficient fuel cell - chemical fuel and oxygen go in (exercise means more use of both), little energy comes out. With the downside of noise and wasting the crew's time. The oxygen\oxidizer part of such tends to be trickier than the fuel one.

 

[Francis Urquhart]

To me it seems like a very inefficient fuel cell - chemical fuel and oxygen go in (exercise means more use of both), little energy comes out. With the downside of noise and wasting the crew's time. The oxygen\oxidizer part of such tends to be trickier than the fuel one.

That's a very interesting way of looking at things. One of the problems on warships is providing exercise facilities for the crew, not least because these days the crew remain below decks most of the time. So, its likely that things like exercise bikes will be on board for that reason so giving them a double use is no great issue. However, the ability of such equipment to produce a meaningful level of power assumes that there is enough space on the ship/submarine to make their use possible. If the ship has enough space, its power demands will be so far beyond the generating capacity that trying to bridge the gap will be hopeless. I can see the generation of a trickle of power to service minor-use electrical equipment. One option might be to make people ride the exercise bike to charge their mobile telephones. Power generation though would be way secondary to keeping the crew fit.

 

[Flintsteel]

The first main problem with RTGs is safety which is why they tend to be assigned to unscrewed vehicles.

Safety? Those things we designed in the 60's to be launched on rockets, have the rocket explode, and then fall back to Earth without breaching? And mostly use alpha-emitters, which can be blocked with a sheet of paper and probably wouldn't give you cancer unless your ate it.

And they're worried about safety?

/boggle

(Okay, most space-based RTGs ain't exactly winners on output, with them mostly being around the 100-150 watts, so I guess the higher-output versions needed for a sub's demands aren't as safe.)

There are alternative reactor designs coming that might change the cost balance but at that point, some discrete silence is in order. .

We talking sterling-cycle mini-reactors like Kilopower, or is Polywell actually still in development?

 

[Deleted member]

SCEs with nuclear power are probably finally viable up to around 100kWe. I've tested a 25kWe SCE, though off a conventional heat source, and it's probably the highest efficiency electricity source as a function of supply heat for the 15 - 50 kWe bracket, and viable up to 100kWe.

 

[bullethead]

Honestly, if Hyman Rickover hadn't been so butthurt about CONFORM (to the point of destroying the research reports) and blocked research into non-water cooled reactors, we might be looking at wildly different designs today. IIRC, stuff like helium cooling was bandied about before Rickover stepped in and killed it.

 

[Deleted member]

If we combined the technology of both Narwhal and Lipscombe we could have an incredibly stealthy coastal nuke sub capable of speeds up to 20+kts, but I don’t think the rationale for the US to build such a boat ever really existed.

Interestingly, that would probably be an ideal design if you wanted a boat for commerce warfare in the modern world, though, i.e., the classic WW1 and 2 submarine function.

 

[Francis Urquhart]

Safety? Those things we designed in the 60's to be launched on rockets, have the rocket explode, and then fall back to Earth without breaching? And mostly use alpha-emitters, which can be blocked with a sheet of paper and probably wouldn't give you cancer unless your ate it. And they're worried about safety? Okay, most space-based RTGs ain't exactly winners on output, with them mostly being around the 100-150 watts, so I guess the higher-output versions needed for a sub's demands aren't as safe.)

Different environment. Those are sudden catastrophic events. In a submarine (or surface ship) we are looking at literally a lifetime's daily hard service in hostile conditions surrounded by people who have an unnerving talent for breaking things. Under those conditions the RTGs degrade. RTGs are fine when we are powering crewless installations but they don't make good companions for people in confined, closed-environment situations. The primary terrestrial use for them was powering un-crewed lighthouses in Russia and for the USAF early warning radars oop north.

For all that, it is worth noting that there have been several accidents with RTGs that have resulted in radioactive contamination including one incident in India that has resulted in a radioactive plume trapped underneath a glacier.

To put the terrestrial power demand/weight balance. into context the Sentinel-100 RTGs used by the USAF weight 1,250 kg and generate 53 watts. Thus to be a substitute for a nuclear reactor used in a submarine, an RTG array would weigh 1,886 tons. I shudder to think at the space demands. Even to be useful for battery charging in a conventional submarine, we would be looking at a 200 - 300 ton installation. In each case that excludes the parasitic weight.

We talking sterling-cycle mini-reactors like Kilopower, or is Polywell actually still in development?

Lot of work going on in a variety of areas. Please leave it there. Military nuclear power systems are a classified area.

 

[Francis Urquhart]

Honestly, if Hyman Rickover hadn't been so butthurt about CONFORM (to the point of destroying the research reports) and blocked research into non-water cooled reactors, we might be looking at wildly different designs today. IIRC, stuff like helium cooling was bandied about before Rickover stepped in and killed it.

Rickover's basic driver in this area was that he understood that if there was a major reactor accident on one of his nuclear submarines, the public reaction would probably kill the submarine fleet. Thus, he always went for the safe option. Having said that we did look at several alternate technologies in the early days. One was a liquid metal cooled reactor which, in theory, was a very good idea. We built a submarine (the 1950s Seawolf) that had a liquid-metal cooled reactor but she was very unsuccessful and was rebuilt with a PWR. The Russians built several submarines powered by liquid-metal cooled reactors and they all failed very badly. At the moment water-cooled reactors offer the best balance of capability, cost, weight and volume within the overriding parameter of being safe. There are other approaches as propulsion for naval vessels (details classified) but AFAIK none yet rival the PWR as a practical solution.

 

[Deleted member]

Welcome to Cool Energy – Cool Energy

coolenergy.com

Here’s a nice public source from a viable SCE company.

 

[Francis Urquhart]

Welcome to Cool Energy – Cool Energy

coolenergy.com

Here’s a nice public source from a viable SCE company.

That's very interesting, thank you. I must look further into that. I have a limited interest in civilian power systems but its primarily in generating baseload power for grids. We're looking at outputs there of 600MW to 1.8 GW, way above military requirements. The primary issue with military units right now is enhancing reliability and reducing space/weight/crew demands rather than any change in basic technology.

I was down at Powergen in New Orleans last week. Poor show but the food in New Orleans is great.

 

[Bacle]

That's very interesting, thank you. I must look further into that. I have a limited interest in civilian power systems but its primarily in generating baseload power for grids. We're looking at outputs there of 600MW to 1.8 GW, way above military requirements. The primary issue with military units right now is enhancing reliability and reducing space/weight/crew demands rather than any change in basic technology.

I was down at Powergen in New Orleans last week. Poor show but the food in New Orleans is great.

Have you heard about the SMRs that NuScale has developed?

NuScale Power | Small Modular Reactor (SMR) Nuclear Technology

We are the global leaders in SMR nuclear technology, delivering our groundbreaking NuScale Power Module to customers in 4, 6, and 12-module VOYGR power plants.

www.nuscalepower.com

I saw these guys when I was researching nuclear power for my aborted Master's in Environmental Management degree. Their pumpless, convection/gravity driven design is rather intriguing, though probably of limited utility on warships or subs. Might be useful for land installations though.

 

[Francis Urquhart]

Have you heard about the SMRs that NuScale has developed?

NuScale Power | Small Modular Reactor (SMR) Nuclear Technology

We are the global leaders in SMR nuclear technology, delivering our groundbreaking NuScale Power Module to customers in 4, 6, and 12-module VOYGR power plants.

www.nuscalepower.com

One of my colleagues has been looking at this class of system and for land use it seems to have a fair level of potential. The problem is that it has a major disadvantage in that it is one of those "ebil nooklir def mashines" that will kill us all. It's almost impossible to get any nuclear things built in the USA right now and unless there is a fundamental change in how people think, its going to be a long time before we see any appreciable in new technologies reaching commercial acceptance. This is a huge pity because nuclear is actually just about the "greenest" technologies there is. At least where carbon emissions are concerned. Personally I think the end of nuclear was just about the worst mistake that has been made from an environmental point of view. But, it illustrates the basic accuracy of Rickover's belief that one nuclear accident will kill an entire industry.

It's worth noting that SSBNs tend to use gravity-fed cooling systems on their reactor to cut down emitted noise (most of the noise from a nuclear power plant comes from the cooling system). So its quite possible that we'll see some of the technology being developed here vanishing into the maw of the military-industrial complex.