Nuclear vs AIP

[amrcg]

Dear all

I have a doubt about the noise characteristics of nuclear submarines vs AIP diesel submarines. In several websites I use to read statements like this:

"A nuclear sub uses a compact nuclear reactor to generate steam to drive a turbine to turn the propeller. Except for modern adaptations, this differs little from old coal driven turbines. They are much quieter now, but they still make a lot of noise. Diesel submarines use reciprocating engines on the surface and while snorkeling, and battery driven electric motors while submerged. The first is noisy, the latter extremely quiet."

My dumb question: Theoretically, couldn't nuclear submarines also have batteries that would be charged by the steam-driven turbine? That would make nuclear submarines even quiter during an action.

Best regards,
Antonio

[TLAM Strike]

The 1st Brit nucs had an electric motor for doing just that (among other things)

[Bubblehead Nuke]

You might not realize it but a reactor plant is not something that you can just turn on and off like a diesel. We would spend about 8 -12 hours MINIMUM doing prestartup checklists and a few hours to actually take the reactor critical and bring systems online.

The Americans did try something like this with the USS Tullibee. It was turbo electric drive with a big honkin electric motor driving the shaft directly. The power requirements are a LOT different when you are just driving turbine generators and not the engines. It supposedly cut the noise level down propulsion plant noise significantly but due to the way it was designed it was not very fast.

Oh, and american subs DO have batteries. BIG ones, but they are a backup for a backup of the reactor plant. (yes, I said backup twice for a reason)

[Smaragdadler]

Originally Posted by amrcg

Dear all

I have a doubt about the noise characteristics of nuclear submarines vs AIP diesel submarines. In several websites I use to read statements like this:

"A nuclear sub uses a compact nuclear reactor to generate steam to drive a turbine to turn the propeller. Except for modern adaptations, this differs little from old coal driven turbines. They are much quieter now, but they still make a lot of noise. Diesel submarines use reciprocating engines on the surface and while snorkeling, and battery driven electric motors while submerged. The first is noisy, the latter extremely quiet."

My dumb question: Theoretically, couldn't nuclear submarines also have batteries that would be charged by the steam-driven turbine? That would make nuclear submarines even quiter during an action.

Best regards,
Antonio

AIP is not Diesel and not every AIP is the same.
Your quote above talks only about 'normal' Diesel vs. Nuclear. AIP means 'air independent propulsion' and it comes in different concepts. There are some 'older' AIP-systems which 'only' allow to run the diesel submerged without snorkel. With most modern 'true' AIP (fuel cell) you don't need the diesel at all.

[Smaragdadler]

AIP - The Early History


Walter Type XVIIB up on the stocks. Pictured above is the German Walter Type XVIIB U-1406, partially dismantled shortly after the end of World War II. U-1406 was turned over to the U.S. Navy as a war prize and soon disposed of, but the Royal Navy later operated her sister ship, U-1407, as HMS Meteorite to gain experience in hydrogen-peroxide propulsion technologies.

Despite their initial successes, submarine pioneers were still eager to find some means to free their boats from the necessity of surfacing frequently for access to the atmospheric oxygen demanded by the gasoline or diesel engines that charged the batteries. A number of approaches were tried, but eventually, open-cycle diesel engines, lead-acid batteries, and electric motors for submerged propulsion became the standard submarine engineering plant that served well through two world wars.

In the early 1930s, however, a brilliant German engineer, Dr. Helmuth Walter (ca. 1900-1980) of Kiel's Germaniawerft, proposed a radical new submarine propulsion plant based on the use of high-purity hydrogen peroxide (H2O2) as an oxidant. In Walter's system, hydrogen peroxide from an onboard supply was decomposed using a permanganate catalyst to yield high temperature steam and free oxygen. Into the reaction chamber was injected diesel fuel, which combusted with the oxygen to yield a mixture of steam and hot gas that drove a high-speed turbine. The exhaust and condensed steam were then expelled overboard. Walter's primary design goal was high underwater speed, rather than long endurance, and indeed, his first submarine prototype, the experimental V80, reached 28.1 knots submerged in its 1940 trials - at a time when conventional submarines were limited to 10 knots or less. Thus, V80, only 76 tons and 22 meters long, also served as an early test bed for studying the dynamics and control of high-speed underwater vehicles.

Later in the war, the Kriegsmarine attempted to scale Walter's prototype up to a useful operational size, but although seven Type XVIIB H2O2 coastal boats were completed before Germany's final defeat, none saw combat. These Type XVIIs displaced 300 tons and were powered by two 2,500 horsepower turbines, in addition to a conventional diesel-electric plant. More ambitious plans to build larger Walter-designed ocean-going submarines, such as the 800-ton Type XXVI and the 1,600-ton Type XVIII were thwarted by the unsuccessful course of the war and the realization that the industrial capacity needed to supply sufficient quantities of hydrogen peroxide could never be achieved. However, the Type XVIII was modified into the highly successful Type XXI "electro-boat," in which larger batteries provided a submerged speed of 17 knots, which could be maintained for 90 minutes. That innovation, and the adoption of the snorkel, yielded a potent combination that strongly influenced the postwar design of conventionally-powered submarines on both sides of the Iron Curtain.

[...]

An AIP Perspective
Although it is a remarkable tribute to Hellmuth Walter's engineering genius that he fielded a fully functional - if troublesome - 5,000-horsepower AIP system in 1945, the maximum power output of current AIP installations is typically on the order of 400 horsepower (300 kilowatts). In comparison, the conventional diesel-electric plant of the U 212 class described above is rated at over 3,000 horsepower, and a typical nuclear submarine propulsion plant produces over 20,000. Since the power required to propel a submerged body varies with the cube of its velocity, it should be apparent that at least for the near future, AIP will be valuable primarily as a low-speed, long-endurance adjunct to the under- water performance of conventional submarines. There is little short-term prospect for AIP to become a primary, full-performance alternative to either diesel or nuclear power. Even the phrase "closed cycle" is something of a misnomer, because except for fuel cells, all AIP alternatives require ejecting exhaust gases overboard, which limits both depth capability and stealth.

However, this is not to minimize the dangerous potential for AIP submarines to complicate seriously both coastal defense and assured access to littoral regions. If their distinctive characteristics are exploited by skillful operators, AIP submarines can be used to telling effect for both short- and medium-range missions. AIP dramatically expands the tactical "trade-space" for diesel-electric submarines. If conditions permit, they can transit rapidly on the surface with-out unduly expending the wherewithal for superior underwater performance. Submerged, they can opt for a long, slow, silent patrol that keeps their batteries fully charged and thus capable of powering speed bursts of significant duration. And by carefully husbanding their resources, they can revert again to slow-speed operation and repeat the cycle several times over weeks of submergence. Moreover, AIP technology is evolving rapidly, and some experts predict, for example, that the power output of a typical fuel cell module could well double or triple in the next several years, allowing an even more advantageous trade-off between underwater speed and endurance.

Their tactical flexibility, their small size, their inherent stealth - and the novel operational paradigms AIP submarines introduce to undersea warfare - will make these new boats a dangerous threat to submariners accustomed to nuclear- or conventionally diesel-powered adversaries. The Submarine Force needs to understand this threat - where it's been, where it's going, what it means, and how to counter it.

more:
http://www.chinfo.navy.mil/navpalib/...propulsion.htm

[Kapitan]

It realy depends on how much you want to spend, and what its going to be needed for.

Germany has no nuclear submarines only AIP ones but they dont get heavily involved in forign politics so thier subs realy have no use for the time being.

Britian on the other hand does and we use our nukes all the time for all diffrent kinds of missions and what not so it does depends on you place in the world.

Personaly id like to go on an AIP submarine not a nuke.

[amrcg]

Originally Posted by Smaragdadler

AIP is not Diesel and not every AIP is the same.
Your quote above talks only about 'normal' Diesel vs. Nuclear. AIP means 'air independent propulsion' and it comes in different concepts. There are some 'older' AIP-systems which 'only' allow to run the diesel submerged without snorkel. With most modern 'true' AIP (fuel cell) you don't need the diesel at all.

I thought that fuel cells were still not efficient enough to allow full autonomy. I thought they operated more like "more efficient batteries" in modern diesel subs. What is the current autonomy of a fule-cell-only sub?

Cheers,
Antonio

[Smaragdadler]

Originally Posted by amrcg

I thought that fuel cells were still not efficient enough to allow full autonomy. I thought they operated more like "more efficient batteries" in modern diesel subs. What is the current autonomy of a fule-cell-only sub?

We had talked about it a little bit in the u31-pic thread. There are lot of rumors but nobody came with hard facts.
This is what Skybird wrote about u212:

Originally Posted by Skybird

The Diesel is very much only an emergency backup. They are not expected to "charge batteries" under normal conditions during a trip, for all energy for board systems and engine is not coming from batteries, but directly from the fuel cells, the traditional diesel-battery-engine-concept cannot be compared to in this case - this is NOT a normal diesel sub with an added fuel cell. The engine is directly powered by the fuel cells. The energy in these fuel cells can only be replenished at harbour, by replacing and/or loading the cylindrical modules that store these ressources (they do indeed look like giant AAA battery cells, ) Normal operation of the the engine and screw is energized by the fuel cell only - always. Top secret propeller and fuel cell makes for so little noise at up to medium speed settings that the sub is described to be "undetectable by contemporary passive sonar even if sensors are just a "Katzensprung" away" (quoting a leading engineer of HDW in an interview with a defense affairs journalist at the beginniong of this year, a guy I once talked to). The same source told him that the "212 is easily the most "non-existing" sub in the water today."
The limited hull size (still much more room than in the 206 and 209) is referring to the roots of the project in the cold war. The 212 hull design was once meant for exclusive Eastern sea operations.

The duration of the sub beeing able to remain submerged without snorkeling or taking ressupplies is top secret, and various sources indicate various time frames from up to 3 weeks to up to 4 months. Since the sub is Germany's top intel gathering platform is is now meant to serve in that role globally, if wanted, and that requires long endurance capabilities. time and again German medias have pointed out that this sub can operate completely indepedent from surface (snorkelling, ressuplying) for "many, many weeks". That'S why some tend to think of it as "a nuclear sub without a nuclear engine."

but whatever - it looks damn sexy.

[BigBadVuk]

Well if Nimitz class is somewhere (if im right) around 1 year of authonomy then i guess subs r around that time also....

And @amrcg even if u order full stop to nuclear sub...manuvering and reactor control room will NOT turn down all the pumps and systems for cooling the reactor, becose that will be the invitation for disaster...Chernobyl II at sea...So u need to keep reactor supplied with coolant all the time even if he is not operating at 100% and CRDM(control rods drive mechanisam-set of graphite rods for controling the fission,something like throtle in plane or car) is in full down position.And even if pumps are all on rubber stands,double insulated from sub external hull they r still noisy so generaly SSNs are louder than SSs..

[Henson]

What is being missed is that the two different platforms fulfill different missions, and especially in the case of the US the requirements we have of our submarines are a lot different than the requirements Japan or Pakistan have for theirs.

We need those legs and that speed to do what we need to do and get where we need to go. Considering where warfare is moving, once you get a submarine to a certain level of quiet it's debateable whether it's worthwhile to go any further now.

We live in brown water. The cold war is over, and so are cold war submarine realities.

[Kapitan]

Not so fast henson, cold war is still a reality, you guys still track trail and moniter russian exercises and submarines.

America is not 100% to blame i can name a few submarines that have been monitering such exercise's including german norwiegen swedish danish french British and American

[Henson]

Originally Posted by Kapitan

Not so fast henson, cold war is still a reality, you guys still track trail and moniter russian exercises and submarines.

America is not 100% to blame i can name a few submarines that have been monitering such exercise's including german norwiegen swedish danish french British and American

I won't confirm that either way.

I would point out that we have no doubt the russians attempt to track US subs, especially our Tridents (Ohio class SSBNs).

It is true however that our focus has moved to other missions, TLAM strike being among them. We train for a large range of possible missions, in all different types of waterspace.

[Kapitan]

I dont need you to confirm this, watching the tv doc documentary says it all, i mean what chance is there of just coincidentaly bumping into a norwiegen spy ship, not to mention a british spy ship as well.

We know all of you try and track us we know where you hide just off the coast, and we know what your doing it for.

Your missions have changed so have ours, our role is to protect our country, our sovrenty, your now taking to brown water to stop these terrorists and we know your not putting much emphasis on tracking our boats so much.

I dont ask for you to confirm you actions or the USN actions, because we and most people here already know that you still track our submarines.

We are also to blame il openly admit we do track your submarines, ohio's are the main goal.

In 1999 we sent two Oscar class submarines too sea to stalk you waters, the mission was a sucsess, it an open mission because you americans made it public, we put the Kursk in the med she was hunted by both british and americans for 3 weeks but you failed to find her.

It took a canadian P3 and for the kursk to have travel over 5,000 miles before she was spotted and moniterd heading home off the icelantic coast.

Another submarine at the same time was spotted first by a merchant ship lurking around the waters of pearl harbour, to confirm you sent out again a P3 which in turn moniterd the ship.

Despite being detected (which was an aim anyway) the mission was sucsessful the primary goal was to show that despite the issues Russia has we can still deploy far and wide, and let me remind you that since this has taken place, patrols have taken an up turning, there has been more of them.

Currently there is around 7 submarines at sea at my best guess, im not ranting here im filling in some detail so please dont take this as a negative post!

The submarines dont number what they used to be, we dont want a war with you we never have (maybe stalin and kruschev did), but i can only say that submariners from Russia admire thier american and british counterparts they hold close respect for you and what your doing, even if it is following them.

[Henson]

Trust me, that respect is reciprocated by all but the youthful, ignorant, or unwise.

We pay attention to anyone who could conceivably be a threat to our interests. No one expects us to do any different.


Incidentally, how would you know if an Oscar was detected? We don't exactly pubicize submarine encounters for reading on the web.

(I saw it on TV, it must be true...)

[Kapitan]

No we know you detected them, infact it was published in the Russian papers, they tv thing i was on about is something diffrent.

In this documentary the captain alleges that they are being spied on, not long after the cameras give a very good close up of the spy ships, and then the narrator translates what the captain says.

i dont take TV to light alot i mean alot of it is katwaddel.

But we understand we are a threat to you (Heavens knows why), but we know what your doing and we let you get on with it, we have no wish for a confrontation.

The reason it was publicised was that was the goal it was to prove to america publicly via the media that russia can still pose a threat so we basical helped compromise our own mission (again i aint a clue why).

Some high officed moscow idiot thought it would be a good idea to send these two submarines in tandem to prove that russia can still pose a threat, in my view it shouldnt have been done, it helped damage relations and got us where we are now in a tight spot.

Im not being youthfull but you do what you do to protect your country and family and i will do the same.

Together we are the same people doing the same thing just diffrent ways, we dont go out there looking for the problem we let it come to us.

As we said to the crew of one spy submarine back in the 1950's "thankyou for the ASW exercise" :rotfl:

In this post im not saying to the USN back off our coast but what i am saying is we know why your doing it, to protect yourself, any right minded person group or government would do that same, so realy no one is in the wrong.

Might i just add also that the two oscar class submarines missions were to be detected, the information is publicly availible but alot is still classified things like the route they took and what they did only the bear basics have been told.