I was intrigued to read that China may have come up with a unique way to recharge submarine batteries while underwater.
China’s new nuclear-battery attack submarine – a unique hybrid boat running on batteries like a conventional sub but which recharges them using a tiny nuclear reactor – could be the ultimate near-shore defence sub, and a big problem for US and allied forces in the western Pacific.
. . .
Most notably the type seems to have a unique propulsion system – one that sidesteps longstanding engineering challenges in order to deliver a quiet attack submarine for near-shore operations, one that can stay submerged for long periods of time in order to preserve its stealth. The Type 041 is reportedly the first submarine with a tiny nuclear reactor that, while too small to power the entire boat, is big enough to charge the batteries for submerged operations.
. . .
With its nuclear-charged battery, a Type 041 might be able to remain submerged for 20 days straight, according to Kirchberger and Carlson. That’s a 10-fold improvement in underwater endurance compared to traditional diesel-electric submarines.
There's more at the link.
This is particularly interesting news given new developments in battery technology, plus new modular small nuclear reactors. The latter are particularly important, because current designs are intended to power a small town, or an industrial facility. If all they have to do is recharge banks of batteries, they can be made even smaller - in effect, miniaturized. It's not inconceivable that they could be reduced to the size of a small motor vehicle, which could easily be installed in a submarine hull in place of conventional diesel engines or air-independent propulsion (AIP) units.
There's another side to that, of course. Some smaller countries such as Iran and North Korea build their own submarines, almost all of them using World War II-vintage diesel engines and lead-acid batteries. They're relatively unsophisticated. If such countries can buy or build small modular reactors, they could possibly build their own nuclear-recharged battery-powered submarines that would offer far greater range and speed than their old-fashioned units. A few such submarines at "choke points" for maritime trade, such as off any one of dozens of major harbors, the entrances to the Suez Canal or Panama Canal, the Strait of Hormuz, the Strait of Malacca or the Bab-el-Mandeb, and maritime trade worldwide could take a massive hit. The relative inefficiency of their old-fashioned batteries, with their lower capacity and endurance, wouldn't matter nearly so much if they could be recharged silently, on demand, without surfacing, by an on-board miniature reactor.
The USA long ago decided that all its submarines should be nuclear-powered. There were good reasons for that, but it's resulted in very, very expensive and complicated vessels, and arguably not enough of them to accomplish all the missions and tasks expected of them. Could nuclear-recharged battery-powered submarines affect that decision, making a greatly increased submarine fleet both affordable and effective? It is to hope . . .
Peter
18 comments:
Very interesting. As a former nuke officer (carrier, not sub), I look forward to reading more.
I wonder if this is really practical.
You still need nuke-trained people to run the reactor, and it needs to be manned 24x7, so the same number of them.
I suppose it's faster to make a smaller reactor, but the shielding is then a larger component of the mass.
It will be a different design, so perhaps it doesn't need that 24x7 staffing though?
The other factor is stealth.
Nuclear sub's reactors make noise. Not a lot, but detectable levels.
The quietest subs in the world (so far) are diesel electrics running on their batteries. Running slow and rigged for silent those things are basically a hole in the water, audio wise.
So with this idea, you get the benefits of a diesel electric (stealth) while mitigating the two major downsides: The need to come to snorkel depth or surface and run very noisy diesel engines to recharge batteries, and the range limitations of having to rely on tanks of diesel fuel.
A design like that could be a game changer. We need to take heed.
Full disclosure, I was never a bubblehead (one of my best friends was COB (Chief of the Boat...senior enlisted man) of a Los Angeles class attack sub, but I was an Airedale) but I did spend one tour of duty in an Anti-Submarine Warfare (ASW) helo squadron deploying on Frigates who's entire purpose in life was chasing down and killing enemy subs, so I do have some passing familiarity with the concepts.
Look up the US Navy's NR-1 to see just how small a nuclear power plant can be and how few operators it takes to run it, but that was a fully nuclear powered deep submergence vessel, not a littoral combat submarine so the energy demands when submerged are VERY different. From the few details in the linked article it looks like the claim is they added something like a SNAP radioisotope generator to provide a trickle charge to the batteries when fully submerged. If the system actually exists that could be a really quiet boat for littoral combat, but would have a hard time catching a carrier group moving at 25+ knots.
If the 041 boat is really the prototype they have years of cleanout and repairs/rewiring before going to sea, it took almost 3 years to repair the USS Guitarro after she sank at the pier.
MM1(SS) Nuc operator
That underwater utility is good news for China, as some of their newest submarines seem to have developed the ability to submerge while still moored at the dockside.
So solly.
😁
Them using a nuke to recharge really isn't the deal, it's batteries that are supposedly 10x better, though are they 10x better then older Chinese ones or the world average, I wonder how they compare to modern Japanese subs.
They wouldn't mater any how to really defend China, they could be a pain to shipping from that area but they can't effectively project into the open Pacific or the Indian Ocean and they have to import massive amounts of food and fuel that we can stop at the source.
Hmmm. Wonder if the ChiComs are using Lithium Ion batteries? If so, well, can't wait until the inevitable battery fire.
Went on the Stennis Aircraft carrier for 'family day'. When f18s started bnusting the sound barrier a shot time after we put out to sea I asked a crew member how they could do that so close to San Diego. According to him we were 200 miles out from land. Carriers do stand up and haul ass.
Definitely a game changer. The Israeli Dolphin II diesel electric submarines have oxygen stored on board for use with fuel cells to prolong their underwater time by a couple of days instead of having to surface or snorkel to charge their batteries every 12+ hours.
Once again, the batteries will be the issue...
I think the Japanese have tested a system where the sub has a diesel for normal recharging but a fuel cell to charge the lithium batteries if ultra quiet ops were needed.
I'm going to disagree here. Let's start with this sentence: "The Type 041 is reportedly the first submarine with a tiny nuclear reactor that, while too small to power the entire boat, is big enough to charge the batteries for submerged operations."
Batteries are storage devices, not power generators. If, to take a random example, the sub uses batteries for three days and recharges on the fourth, the NPP has to be sized to generate 4 days worth of power in one day. That's ignoring the losses incurred in both storing and depleting batteries, which add to the NPP requirements.
Also what happens to the NPP while underway using batteries? I doubt it could be totally shutdown like a diesel engine. It would probably be in a quiescent state at say 5-10% power. Making noise. Requiring constant monitoring by dedicated crew.
It seems an unnecessary complication. The only advantage I can see is if NPP are notably louder than electric. But this assumes that while on standby mode the NPP is quieter too. The extra crew resources, cost and complexity seem to be not worth the questionable benefit.
"Went on the Stennis Aircraft carrier for 'family day'. When f18s started bnusting the sound barrier a shot time after we put out to sea I asked a crew member how they could do that so close to San Diego. According to him we were 200 miles out from land. Carriers do stand up and haul ass."
It is pretty amazing how fast 100k tons of steel can be pushed through the water when they really put their minds to it.
Actual top speed is classified, but they list the top speed of a US Aircraft carrier as 30+ knots. That "+" is carrying a heavy load.
I did a couple of short hops on the Stennis back when it was still on the East Coast.
"Also what happens to the NPP while underway using batteries? I doubt it could be totally shutdown like a diesel engine. It would probably be in a quiescent state at say 5-10% power. Making noise. Requiring constant monitoring by dedicated crew."
"The only advantage I can see is if NPP are notably louder than electric. But this assumes that while on standby mode the NPP is quieter too."
Those are excellent points.
Subs don't necessarily have to stay dead quiet all the time, only within detection range of the sub or ship that's hunting them, so they could run the NPP at full power, providing recharging to the batteries even while deeply submerged or trying to evade detection. Based on the power density of nuclear power plants, I'd assume that a small one could easily exceed the discharge rate of a the batteries at, say, half speed propulsion. In that case, they could be recharging while at a "safe" distance from their adversaries and only put them in "standby mode" when within detection range.
Which makes your second point highly relevant: how quiet is the small nuclear plant while in "standby mode"? Or maybe there is no "standby mode" and the plant is just small enough that it makes minimal noise to begin with?
I don't know, but those are very valid points.
Incidentally, speaking of power density. When the first Nuclear Aircraft Carrier was built, nuclear technology wasn't what it is today so the reactors weren't as efficient, plus, since driving a ship that big with nuclear power had never been done before, they really weren't sure how many reactors would be needed to fully power the ship, so they went with overkill. The USS Enterprise (I served ship's company on her for a year) had eight nuclear reactors (four banks of two reactors).
Nimitz class and subsequent carriers have two.
@RickT
The SNAP reactors are all thermo-electric generators, meaning they use decay heat from radio-isotopes to heat thermocouples (not the typical bi-metal thermocouples, current designs use bismuth-telluride or lead-tellurium semi-conductor thermocouples to increase the junction area).
The output is low, very low, the largest I see is 55KW.
Not enough to recharge the massive battery banks required to drive a submarine in any reasonable time.
These reactors are used to power satellites, etc, not a high current load like a submarine propulsion system.
The math doesn't support it.
Have a Good Day👋
👽
Peter
Submarine reactors ARE Small reactors.
They also require pumps to move the coolant in at least some power modes.
They also generate heat to produce steam to drive turbines to drive the propellers &/or generators.
This is how the heat from the nuclear reaction is converted into rotational energy to perform work.
The pumps, turbines, etc are machinery that produces noise.
An electric motor driving a propeller is much quieter.
Have a Good Day👋
👽
Again, excellent points from other commenters that provide food for thought.
I'm not a nuc and wasn't even a bubblehead so I don't understand the technology in any detail...Submarines were just targets to me and my perspective grows from trying to find them and kill them.
Sneaky bastards they were.
Post a Comment