OT Nuclear U-Boats; how do they condense the steam?

Two points. You have to dump "low temperature" heat somewhere to have a thermodynamic cycle from which you extract energy. In a sub, the only place is the sea.

IIRC the Soviets have used fast reactors in subs, I think with lead or lead/bismuth cooling rather than sodium. I think everyone else uses pressurised water reactors.

While mixing sodium and water is bad news, the death knell for the Dounreay Prototype Fast Reactor was corrosion, more accurately stress corrosion cracking, on the *water* side of the sodium to water heat exchanger where the steam is raised. This is hot, very pure water which poses more materials challenges than the the cold seawater-to-steam condenser.

Drill a few holes in the propeller....

or adopt WW2 acoustic mine sweeping technology by fitting a Kango vibrating hammer to the hull of the ship ;)

From

" In late October the recovery and exploitation of an acoustic mine ? found ashore in the mouth of the River Ogmore near Porthcawl - allowed a more effective sweep to be developed. This was the Kango vibrating hammer ? known as the ?SA? (Sweep Acoustic) that was being widely fitted before the end of the year and was to see significant success fitted either in the bows of a vessel or streamed outboard. The risks remained significant though; the minesweeping trawler RADNOR CASTLE had to be beached off Plymouth following a too-close detonation and in December HM Trawler COURTIER detonated 4 acoustics in swift succession, the last one breaking the legs of 4 crew members and putting the trawler in dock for several months. A less conventional minesweeper also incurred damage in late December 1940; the fast Isle of Man Steam Packet SS VICTORIA had already set off 8 or 9 mines during her transits back and forth to Liverpool, but on the 27th the detonation just off the Douglas Bar Light was a little too close and she had to be towed back to port although, in this instance, no casualties were reported. "

and sinking a war ship that the Japanese had failed to do in Pearl harbour.

I am sure the *point* of the new deal is that the Astute-like subs will give Australia very much better intelligence capability on Chinese activities in the South China Sea and elsewhere. Undoubtedly the information will be shared completely with the USA and the UK. It also means Australia and its regional friends will have more credibility in protesting about Chinese activities to the UN, thus giving expansionist Chinese more diplomatic headaches.

It's a bit like Teddy Roosevelt's "Speak softly and carry a big stick".

Not just the public. Having four (with two at sea much of the time, even if only one is notionally on service duty) gives an aggressor who has spotted one the Dirty Harry dilemma "Do you feel lucky, punk?"

Yeah right! Good point. An aggressor on the USA can be asked: "Can you destroy only 2,800 of my possibly deployed nuclear weapons or can you get all 2,821." 21 missed would be enough to devastate and nation.

There is no need for nuclear deployed missiles on subs. It makes no discernable difference to the viability of detering a first strike against the US.

Subs do give the USA a better chance of launching a first strike against somewhere like North Korea.

Why somewhere like the UK would want to put all its eggs in one basket (or maybe two baskets) is also a puzzle.

Not to me. Look up why Atlee's inner cabinet started the independent weapons programme. And hardly one basket, as Galtieri found to his cost.

newshound wrote

There is no point in us having stupidly expensive subs for that.

The US is quite capable of proving that intelligence with what they already have.

Sure, but the USA doesn?t need it, they already have vastly better sources of that.

That?s bullshit too.

They don?t give a damn about what anyone thinks about what they are doing there, or about the Uyghurs either.

And those subs are a stupidly expensive way to do that anyway. FAR better things to spend that sort of money on.

It isn't a big stick in our case. It isn't even a twig.

Bollocks

You may THINK you will get most of the silos, you KNOW you wont get any of the subs

I don't see why you would say that. Subs can be tracked. The idea that a technology/technique will emerge that can be used to effectively locate all submarines is not that fanciful.

Audio. A network of listening devices. Some other property, I don't know what it is, but with advances in technology I wouldn't rule it out.

The problem is similar to computer security, if you give an opponent a clear attack vector they can hone their techniques.

Pancho wrote

Because its true. Novel concept I realise.

No they cant when out in the open ocean. That?s the whole point of them.

Fraid so.

Not feasible over the entire oceans and no way to be sure it?s a sub with nukes in it either. Easy to fake audio signatures.

Clearly not there now.

Nope, nothing like that.

How odd that no one has done that with nuke missile subs.

Of course they can. They can be followed from base.

[snip]

How would you know if they had done it?

If it were that easy we wouldnyt bother with subs at all.

Its been done. In fact I worked on it back in the 1970s. rubber coated hulls, very slow propellors, down deep. Totally undetectable.

Same goes for thermal signature. You cant 'see' it through a lot of layers of water . And teh sub can run on batteries even if its a nuke,

I can assure you, they do, but I can also assure you, that a sub sitting at depth with engines off is almost impossible to detect. And there are limits to how much of the sea you can litter with sonobuoys.

>

Pancho wrote

Nope, no way to do that. All you know is that they have left the base.

The operation that can do that would stop building any more of them.

???? 16/9/2021 4:49 ?.?., ?/? gareth evans ??????:

well, the expected answer is with sea water, the same "coolant" that convential ships use. I read once a german article about the sinking of the US submarine "Thresher", that was designed to go deeper thna usual, and that was not combined with welding of its pipes, instead of soldering, to withstand the higher pressures involved, also they needed a "clean room" to work, so it's possible that a speck of dust sank the

300 m submarine! Also that it needed a more powerful air compression system, so it could "blow" its ballast tanks in distress, especially following a reactor SCRAM.

Two theories, one official and one unofficial, are very well described here.

It is true that the Thresher had brazed heat exchangers, which showed faults in subsequent boats. I don't see any justification for the "speck of dust" claim and I don't think the Thresher was particularly designed for deeper diving, although this aspect of performance is normally classified. It has been surmised that they were unable to "blow" the tanks because of ice crystals blocking the lines.

I thought the sequence was:

1) Brazed joint fails allowing ingress of sea-water while they were at test depth.

2) Sea water shorts some circuits leading to reactor scram

3) Attempts to blow tanks fail because expanding air cools so much that moisture within it freezes and jams the valves, preventing blowing of tanks

4) Lack of reactor power prevents boat being driven towards surface using engines, boat sinks instead

Yes, that was the official theory. I believe another error was that there were still debris strainers in the air lines that should have been removed after commissioning, and that these contributed to the blockage by ice crystals. I think it is more likely to have been pipe blockage than valve jamming, you would only get crystals once the valves were open and the air was flowing.