Modern Diesel/Electric and AIP Subs vs Nuclear Subs

[burndaddy02]

I'll apologize in advance if this topic has been done elsewhere, I'm new to the forums. I couldn't find the same discussion topic in a search.

 

Some attention has been paid, on and off, to the modern Air Independent Propulsion Submarines that are popping up around the world. They are smaller than nuclear subs, can operate in littorals perhaps more easily. They can become "holes in the water" longer in some cases than the traditional diesel/electrics because of these 'alternative' methods of power and propulsion that are popping up.

 

The question, do you think nuclear powered navies, like the U.S. Navy, should invest in these kinds of assets? The same question could easily be aimed at other nations as well. What are your thoughts on the pros and cons here?

[Eyeless_Camper]

Modern non-nuclear submarines are potentially stealthier than nuclear submarines; a nuclear ship's reactor must constantly pump coolant, generating some amount of detectable noise. Non-nuclear submarines running on battery power or Air-independent propulsion, on the other hand, can be virtually silent. While nuclear-powered designs still dominate in terms of submerged endurance and deep-ocean performance, the new breed of small, high-tech non-nuclear attack subs are highly effective in coastal operations and pose a significant threat to less-stealthy nuclear subs and ships.

[LightningStriker911]

i never knew the US Navy have a nuclear powered navies.

[Tanz]

While AIP powered Subs would be a good thing for the US in the economics times..it wont happen anytime soon. Yet there have been talks of us building them for other countries.

SSNs and certain SSBNs can be very loud but dead silent when they want to, as can these newer SSKs.

[Crag_r]

Depends on the intended role of the sub, an who it will be going up against mainly... and Cost

[thegreenbaron]

My question is: how would we build a submarine for freight?  I'm thinking a minimum of 200 tonnes to make it at least somewhat profitable, since we're not smuggling things like cocaine with it.

[Crag_r]

thegreenbaron, on 09 November 2012 - 01:27 AM, said:

My question is: how would we build a submarine for freight?  I'm thinking a minimum of 200 tonnes to make it at least somewhat profitable, since we're not smuggling things like cocaine with it.

Well the Russian's were considering converting remaining Typhoon class subs to carry cargo, though only 15,000 tons of cargo, and removed Missile tubes.

[thegreenbaron]

Crag_r, on 09 November 2012 - 03:30 AM, said:

Well the Russian's were considering converting remaining Typhoon class subs to carry cargo, though only 15,000 tons of cargo, and removed Missile tubes.

Yeah, but that was with nuclear typhoon class boats.  I'm talking purpose built ships.  AFAIK there only have ever been a few of those, and the USN sank all of them it captured at the end of WWII, along with the I-400's.

[JeeWeeJ]

The Germans had a cargo U-Boot in WW1, the Deutschland:

[MM2ss]

I do not believe that the AIP or DE submarine is appropriate for the USN at this time, based on our mission statement and our methods of operation.  Essentially, our naval doctrine makes the nuclear submarine the better choice for the USN.  If we were in the market for smaller, shorter ranged submarines, then the AIP or DE boat would be a potential candidate.  However, the way we utilize submarines requires long range and high speed capability which the current DE and AIP designs do not meet.

 

The case against the DE submarine is simpler than the case against AIP boats, so I will start there.  A DE boat would be a poor choice of vessel for supporting a carrier group, the need to run at high speeds for extended periods of time would rapidly deplete the batteries and speed is greatly limited when you have things like snorkel tubes, periscopes, and antennae poking up through the surface of the water.  Thus, for supporting carrier groups the DE is a no go.  Likewise, the need to go to periscope depth to recharge batteries makes the DE less effective for extended tracking of hostile subs.

 

AIP is another story all together.  Per my resources, there are four basic types the USN has looked into.

1) Closed-cycle diesel engines, generally with stored liquid oxygen (LOX)

--Despite the additional supply complication of needing regular replenishment of cryogenic oxygen and inert gas, there are logistics advantages in retaining standard diesel engines and using normal diesel fuel.

 

2) Closed-cycle steam turbines

--Low Rankine efficientcy, in fact the lowest of all the AIP options.  High oxygen usage as well.

 

3) Stirling-cycle heat engines with external combustion

--The Stirling-cycle engine forms the basis of the first AIP system to enter naval service in recent times. The Swedish builders, Kockums Naval Systems, tested a prototype plant at sea in 1989, and today, three Swedish Gotland-class boats are each fitted with two adjunct, 75 kilowatt Stirling-cycle propulsion units that burn liquid oxygen and diesel fuel to generate electricity for either propulsion or charging batteries within a conventional diesel-electric plant. The resulting underwater endurance of the 1,500-ton boats is reported to be up to 14 days at five knots, but significant burst speeds are possible when the batteries are topped up.  (NOTE) Again, we are looking at requiring liquid oxygen, which cannot be made on the boat, so long range and long term operations are going to be limited with this...

 

4) Hydrogen-oxygen fuel cells

--This is the interesting one.  Fairly high efficiency, low temperature, little wasted heat energy.  Unfortunately, it looks to be very costly...also, while efficient, they are also not very strong individually...

There are several alternative configurations, but for submarine propulsion, so-called "Polymer Electrolyte Membrane" (PEM) fuel cells have attracted the most attention because of their low operating temperatures (80° Centigrade) and relatively little waste heat. In a PEM device, pressurized hydrogen gas (H2) enters the cell on the anode side, where a platinum catalyst decomposes each pair of molecules into four H+ ions and four free electrons. The electrons depart the anode into the external circuit - the load - as an electric current. Meanwhile, on the cathode side, each oxygen molecule (O2) is catalytically dissociated into separate atoms, using the electrons flowing back from the external circuit to complete their outer electron "shells." The polymer membrane that separates anode and cathode is impervious to electrons, but allows the positively-charged H+ ions to migrate through the cell toward the negatively charged cathode, where they combine with the oxygen atoms to form water. Thus, the overall reaction can be represented as 2H2 + O2 => 2H2O, and a major advantage of the fuel-cell approach is that the only "exhaust" product is pure water. Since a single fuel cell generates only about 0.7 volts DC (direct current), groups of cells are "stacked" together in series to produce a larger and more useful output. The stacks can also be arrayed in parallel to increase the amount of current available.

(NOTE) 0.7 VDC per cell...it is going to take a whole heap of cells to run a boat...

[sheep21]

i guess for a navy such as the US Nuclear boats give them the ability to deploy boats anywhere across the globe at high speed without having to worry about batteries and the like, diesal boats i would think are better for navies which stick to general patrol areas, Canada has the Upholder class and generaly patrols NW Atlantic, NE Pacific & Arctic oceans. No real need for world wide deployment and cheaper to run.

[SG_ONeill]

This reminds me of a movie called "Down Periscope" in which a disgraced U.S. Navy captain is ordered to participate in a war game to test the Navy's defenses and is placed in command of the USS Stingray, a WWII Balao class diesel submarine. In the movie, the Stingray's captain managed to evade the fleet using unconventional tactics and sink a dummy target in the Navy's home port.

[Carrier_Enterprise]

Not all countries need large nuclear subs to patrol their coastlines.

 

The US likes being able to drop a nuke or some seals any where in the world undetected.

[slackware1995]

Eyeless_Camper, on 08 November 2012 - 05:53 PM, said:

Modern non-nuclear submarines are potentially stealthier than nuclear submarines; a nuclear ship's reactor must constantly pump coolant, generating some amount of detectable noise. Non-nuclear submarines running on battery power or Air-independent propulsion, on the other hand, can be virtually silent. While nuclear-powered designs still dominate in terms of submerged endurance and deep-ocean performance, the new breed of small, high-tech non-nuclear attack subs are highly effective in coastal operations and pose a significant threat to less-stealthy nuclear subs and ships.

"A nuclear ship's reactor must constantly pump coolant" has been false for many decades. Even with using pumps, these boats are incredibly quiet. In fact, it's easier to find one by the lack of noise than by the noise created.

Second, the only time a DE boat can be quieter is when it runs on batteries. With batteries, you generally have a choice, very slow and quiet with decent endurance; or fast and noisy with minimal endurance.

Many people just don't understand the amount of money/technology the US has placed into sound dampening technology. As this poster shows, they don't understand how a nuclear power plant works. US SSBN's are incredibly quiet. The fast attack boats are outfitted with either a "slow" quiet propeller, or a "fast" noisy one.

For the US, to me the simple solution would be to move from current designs to a Nuclear-Generator-Battery-Motor design. In essence, you could be incredibly quiet while charging the batteries and still be at 100% effective fighting, yet have the option of bringing the Nuclear reactor to near 0% and run off batteries for even more "quiet".

[Crag_r]

slackware1995, on 30 May 2013 - 09:18 PM, said:

"A nuclear ship's reactor must constantly pump coolant" has been false for many decades. Even with using pumps, these boats are incredibly quiet. In fact, it's easier to find one by the lack of noise than by the noise created.

Is that why those noisy and old Canadian/Australian/Swedish/Japan/Dutch DE subs are always beating their US nuclear powered counterparts in war-games?

[slackware1995]

Crag_r, on 30 May 2013 - 09:33 PM, said:

Is that why those noisy and old Canadian/Australian/Swedish/Japan DE subs are always beating their US nuclear powered counterparts in war-games?

You mean the coastal wargames where the DE boats have other design advantages? IE. smaller, sonar designed for coastal environment?   Move those DE boats out to open ocean, and things change significantly. Your statement is about equivalent to saying a Cobra beat a F15 in wargames, but omitting the fact that the wargame was held in the grand canyon, with an upper limit on height of 200 ft below the rim of the canyon.

Let me put it this way. The US in the past had a small nuclear submarine that went up rivers without being detected. There have been rumors that the russians put nuclear subs into the Puget Sound, San Diego Bay, and other such areas. Amazingly, in the late 80's I was in the Olympic mountains and witnessed the US navy firing depth charges near Port Angeles. I really wish I'd have had a camera with me for that.

[UmamiSalami]

JeeWeeJ, on 09 November 2012 - 04:21 PM, said:

The Germans had a cargo U-Boot in WW1, the Deutschland:

A surprisingly good idea considering their war situation. The value of the cargo carried on its first voyage exceeded its construction cost.

[UncleDaddy]

AIP subs are perfect for a greenwater navy, but for a big blue water navy like the US, nuclear is the way to go.

[Eyeless_Camper]

slackware1995, on 30 May 2013 - 10:05 PM, said:

You mean the coastal wargames where the DE boats have other design advantages? IE. smaller, sonar designed for coastal environment?   Move those DE boats out to open ocean, and things change significantly. Your statement is about equivalent to saying a Cobra beat a F15 in wargames, but omitting the fact that the wargame was held in the grand canyon, with an upper limit on height of 200 ft below the rim of the canyon.

Let me put it this way. The US in the past had a small nuclear submarine that went up rivers without being detected. There have been rumors that the russians put nuclear subs into the Puget Sound, San Diego Bay, and other such areas. Amazingly, in the late 80's I was in the Olympic mountains and witnessed the US navy firing depth charges near Port Angeles. I really wish I'd have had a camera with me for that.

HMS Gotland managed to snap several pictures of the USS Ronald Reagan during a wargaming exercise in the Pacific Ocean, effectively "sinking" the aircraft carrier. The exercise was conducted to evaluate the effectiveness of the US Fleet against diesel-electric submarines, which some have noted as severely lacking.

I dont think 2 weeks in the Pacific Ocean is coastal, and sinking US carriers and submarines during that time  :eyesup:

[JeeWeeJ]

I've read multiple stories of Australian, Dutch and Swedish (and possibly others) diesel-electric subs annihilating US carrier taskforces during NATO (and other) exercises in open water. A DE sub might not have the range of a nuke, but in capable hands it can be just as deadly, if not deadlier.

 

With a well trained crew even the crappiest machine can be a weapon of mass destruction.

[Eyeless_Camper]

Well said, Jee  :great:

[MM2ss]

The real kicker on the DE vs nuke sub is quality of crew.  You could always spot guys who had been stuck on the Parche, they carried themselves a particular way and their sound discipline was top notch.  You also had crews with no sound discipline (don't worry Scranton, I won't mention you guys during TRE...oops).  Most crews fall somewhere in between those two extremes.

 

Now, if you have a good crew it doesn't much matter if you are a nuke or diesel.  You will be pretty darn silent relative to the water.  Where the nuke boats tend to have the advantage is when they can make full use of their often great depth of operation, their greater submerged endurance, and when needed their greater underwater speed.  The DE's have the advantage in operations where you need to be a little quieter, or where you do not need to stay under (including snorkel tubes, I mean nothing breaks the surface) for great periods of time (I just missed on triple digits, we did 98 days completely below water, not even a periscope).

 

Now, case in point regarding crew qualities.  As people know, submarines tend to do things like track other submarines when they are at sea.  I have tracked both diesel and nuke subs.  We were able to track both at similar ranges.  The DE was easier to pinpoint because it had to snorkel every few days.  The nuke boat, well, they had a really lousy watch section, we got a real good update on them about every 18-24 hours.

 

With a good crew that nuke boat would have been harder to track, as there would have been fewer or no transients.  We would have had to get closer or lock in on a few components to keep tabs.  The DE, well the snorkeling routine helped a great deal, and it would not matter what kind of crew they had, they would have needed to snorkel eventually.  We locked in on some of the aux gear and tracked them that way.

[Eyeless_Camper]

"Snorkel every few days"

 

What kind of submarine was that?

Our Gotland can operate without the need for a Snorkel for

"Submerged endurance is dependent on the amount of liquid oxygen stored on-board and is described as "weeks"."

So 2 Weeks+

[MM2ss]

Iranian sub, with a less that stellar crew, Kilo class (not the improved Kilo either).  Likely they could have stayed down longer had they elected to operate at say 3-5 knots instead of trying to find us and running around at about 10 knots.

[Eyeless_Camper]

Ah, that explains it all  :tongue: