A type 039C Yuan-class submarine setting sails somewhere.
Yuan Class AIP & Kilo Submarine Thread
- Thread starter Jeff Head
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So a thought. What if you attached a mirco-scale nuclear reactor to the submarines? There's designs for 1-2 megawatt mirco scale nuclear reactors small enough to fit on a the back of a truck, are cheap and are safe enough to just sit for years without much maintenance. They could be used to charge the batteries. Could be a game changer for smaller submarines. Hell there was a paper by Chinese scientists for a cheap mass produced nuclear reactor for use in torpedoes, giving just 84 kilowatts of power. Just hook it up and extend your mission duration for weeks.
Or maybe a RTG? A large enough one could provide a kilowatt. Small but it's constant, very very safe and the actual RTG would be small enough for you to carry, since they don't need active cooling. Just hook it to the ship's battery and get a constant but small charge. Over days it could add up, maybe extend the underwater duration by a day or two.
Or maybe a RTG? A large enough one could provide a kilowatt. Small but it's constant, very very safe and the actual RTG would be small enough for you to carry, since they don't need active cooling. Just hook it to the ship's battery and get a constant but small charge. Over days it could add up, maybe extend the underwater duration by a day or two.
1 kW would take 4 days to charge a single Tesla with 100 kW*hr battery packs. A Tesla only needs to drive around 2 tons. A sub is 2000 tons.
Historically, subs need 8 MW diesels for 800 km range on 1 charge at 8 knots.
So if you want a good mixed combined nuclear/diesel sub, 1 MW to slowly recharge batteries while submerged + a 4 MW diesels for fast charging is not that bad.
Such a reactor exists at 10 MW.
The problem is extraction of the energy in a silent way that doesn't take up too much space. The only real possibility seems to be a nuclear powered Stirling engine, as turbines are too large and noisy to work, while Stirling engines have been proven on SSKs.
Stirling engines are 15-30% efficient, so worse than diesels, but doesn't matter much here since you can keep it running permanently. A 10 MW thermal reactor at 20% electrical efficiency is good enough.
So yes it is a possibility with existing tech to make mini-SSNs integrated into a diesel sub - diesel for sprinting, reactor for ambush. Whether the marginal cost over a pure diesel and the performance decrease relative to a pure SSN is worth it, unknown.
I looked at the numbers regarding the Type 214. They don't make sense. On the wiki page, it writes that there are 2 engines. Then there is a parenthesis after them that specifies 3.96 MW. I checked the engine model and I found that engines are rated at 2000 kW. So the number in the parenthesis is the combined power of two engines. Regarding underwater on battery range... It is simply impossible. 420 knots at 8 kn would mean a 52.5 hour endurance at 8 kn. Let's look at few other subs to see how impossible this is for a sub that uses lead-acid batteries.
Collins Class: 400 tons of batteries. Has electricity storage at around 12 MWh. Can travel submerged for 120 hours at 4 kn. This translates to a 100 kWh power use per hour, hotel load included.
Soryu Mk1 class: A bit lighter sub on the surface, and has AIP. But has a higher submerged displacement and is more modern. Has a battery around 350 tons.
Attack-class: A 700 ton battery was planned. 4500 tons surface displacement no AIP.
So I think a 200-210 ton battery is a reasonable assumption for the Type 214. With more modern lead-acid batteries that would mean energy storage of around 7 MWh. That would mean a consumption of around 135 kW at 8 knots. That is impossible. Something around 350 kW is more likely for the said speeds.
antiterror13
Brigadier
China's Li-Ion battery is the best in the world, and especially Sodium Ion battery, definitely China is the best (CATL)
The best Li-Ion battery have a density of roughly 250 Watt-hour per kg while Sodium is a bit less at 165 Watt-hour, but safer and cheaper
So 700 ton battery would give you
* 175 MWh for Li-Ion or
* 115 MWh for Na-Ion
Okay 700 ton Li-Ion battery is not realistic for Subs as the volume would be huge.
Just make it 150 tons, I think realistic enough (volume wise would be around 90M3)
* 38 MWh for Li-Ion or
* 25 MWh for Na-Ion
would that be enough for Yuan?
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In addition to what FairAndUnbiased said, the moment you introduce nuclear into the equation, your costs goes up multifold, so it doesn't make sense to have a nuclear power unit 10% the power of a classical SSN and expect to only have 10% of the purchase and 10% of the maintenance costs. Your 1-2 MW reactor will still require you to have highly skilled nuclear power engineers on the crew, nuclear fuel cycle procedures, radiation shielding, reactor management systems, isotopic gas and fusion byproduct management systems, etc. By that point you might as well go full SSN due to the sunk costs. This is also why small localized nuclear power plants have not taken off for land based utility power generation.
I think 300 tons is a more reasonable estimate for the Yuan. Battery-pack energy density would be closer to 150 Wh/kg for Li-Ion if we look at what's being marketed for underwater commercial applications. So 45 MWh is a quite reasonable guess for a state-of-the-art Yuan. If we look at more mature products, the Yuan's electrical energy storage would be around 33 MWh. So 14-16 days of endurance at 4 knots and 60-70 hours of endurance at 8 knots. So ranges are ~510 kn for mature batteries and ~670 kn for recent batteries.
Let's look at the leaked slides about the Korean KSS-III sub. The on-battery range is likely stated for an 8 knots vessel speed, as Germans do. This sub has AIP, has a surface displacement of 3350 tons, and is a new design. We see an on-battery range of around 850 kn. Compatible with my speculations regarding the Yuan.
I think it might depend on how tech evolves. A thermal power plant running a coal fired steam turbine and a car are both fossil fuel fired, but the car is operable by 1 person while the coal fired steam turbine needs a team of full time engineers and technicians to keep running.
There are some modular reactors like pebble bed gas cooled types that are simpler, safer and less prone to failure than water cooled types, but have had limitations on maximum power generation relative to water cooled ones when staff is available.