Chinese Unmanned Underwater Vehicles (UUV)
- Thread starter by78
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TWZ has an article now on this large UUV
one of the most interesting things
3000nm at 6 knots would be mild. That means 500 hours of 6 knots cruising or 20+ days without surfacing just on battery power alone. Amazing how much these things can last longer without having to accommodate humans.
The crazy thing is it still has a diesel engine that extends endurance to probably 2-3 months at sea.
If they actually remove the diesel engine and just do batteries, you can add another expand battery size by probably another 1/3. And then if you reduce the cruise speed to 4 knots, sub can conceivable stay in the water for 40 days and spend 4000 nm roaming.
It would be wilder if they put Stirling in there and it never has to surface.
So my other theory is that since it needs to surface probably once or twice a day to communicate with satellite, that's time for it to charge. If it can charge like 10 minutes a day while communication with satellites. Over 20 days, it'd charge for 200 minutes -> 3 2/3 hours. That might be enough to keep it going. So maybe there is a purpose for diesel generator
500hrs of cruising is quite long when using it's energy, the most scary part would be how much time it can lay on the bottom waiting on battery ? With a long buoy antenna for mission update it could become quite a foe.
AssassinsMace
Lieutenant General
I wonder if there's some communication issue going on with unmanned vehicles. You have incidents of Chinese fisherman catching in their nets US UUVs. Also there's that report that the US has cancelled all their "long" range UCAV projects but keeping the loyal wingman programs. There was that report years ago on the mishaps US UAVs have where a lot of them have accidents like flipping over as soon as they takeoff and the pilots are halfway around the world. The Chinese seem to be undeterred or they have something the US doesn't in regards to keeping communication.
that's why I think they use 1000 to 3000nm at cruising speed of 6 knots. In most cases, it's not going to be cruising at 6 knots. It's probably staying stationary, which should use much less power. So, it's entirely possible for it to go 35-40 days without surfacing imo.
this UUV is too larger for that to be a consideration
Its perhaps worth pointing out speeds in the low single digits are very quickly "stationary", ie required just for station keeping, considering oceanic currents. For the same reason the speeds attainable for SSKs on AIP are effectively just to stay in the general area of operations, but not useful for any sort of transits at "cruise" speeds.
by78
General
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btw, 400kW is like really in the wheelhouse of your typical higher end PHEV or REEV out of China. But the battery pack is a lot larger than your NEV. I saw some 1100V generator and motors out of Zhuhai airshow. Putting that type of system in this is super easy. The discharge speed of battery is going to be under 1C for pretty much 90% of the battery SOC. As such, there is going to be very little heating done to battery, so you can pack it pretty tight with LFP. And you can use the higher density and lower discharge type that are quite cheap these days. And in a couple of years, you can stick SSB LFP here and it will have like 2 to 3x the energy density. These unmanned submarines are going to be a beast soon enough.
Also, I am just glad to see submarines going with LFP battery over lead acid batteries. Charging speed and charging cycles will be so much better.
Think about it this way, the weight of sub is 380 to 450t. Let's say 150t of that is battery pack.
If we use the current standard for high density LFP chemistry at pack level. That's about 180 Wh/kg -> 180 kWh/ton
180 * 150 = 27MWh
Cruising at 6 knots has max of 3000nm range. 3000nm/6 knots = 500 hours.
so 500 hours drain lets say 27MWh -> 6 knots drain around 54 kW
Let's say they are actually more conservative and battery pack is more than 140kWh/ton -> 140 * 150 = 21MWh. Let's say 20MWh to make it easy, then 6 knots still drain around 40 kW. That seems more reasonable for a submarine of this size.
But there does seem to be some upside here. Using solid state battery could easily raise it from 20MWh to 60MWh battery pack in a few years.
And if we translate this to regular 3000t submarine, it's kind of crazy to think that such a sub with 15% of its space dedicated to battery packs could have easily a 100MWh battery pack. If it operates at 1MW in low cruising speed, it can go 4 days before needing to charge. And if you remove AIP and put like a 600t battery pack in submarine using density of 400 kWh/ton, that is 250MWh of battery. At 1MW cruising speed, it can go 10 days without needing to surface to charge.
Think about it this way, the weight of sub is 380 to 450t. Let's say 150t of that is battery pack.
If we use the current standard for high density LFP chemistry at pack level. That's about 180 Wh/kg -> 180 kWh/ton
180 * 150 = 27MWh
Cruising at 6 knots has max of 3000nm range. 3000nm/6 knots = 500 hours.
so 500 hours drain lets say 27MWh -> 6 knots drain around 54 kW
Let's say they are actually more conservative and battery pack is more than 140kWh/ton -> 140 * 150 = 21MWh. Let's say 20MWh to make it easy, then 6 knots still drain around 40 kW. That seems more reasonable for a submarine of this size.
But there does seem to be some upside here. Using solid state battery could easily raise it from 20MWh to 60MWh battery pack in a few years.
And if we translate this to regular 3000t submarine, it's kind of crazy to think that such a sub with 15% of its space dedicated to battery packs could have easily a 100MWh battery pack. If it operates at 1MW in low cruising speed, it can go 4 days before needing to charge. And if you remove AIP and put like a 600t battery pack in submarine using density of 400 kWh/ton, that is 250MWh of battery. At 1MW cruising speed, it can go 10 days without needing to surface to charge.