Will the U.S. Navy Build Stealthy AIP Submarines?

[Onkel Neal]

The U.S. Navy has not built diesel-electric submarines since the late 1950s, instead investing itself into an all-nuclear powered submarine force. Will a slew of modern advancements in AIP (air-independent propulsion) technology prompt the Navy to reconsider its stance?

A conventional, diesel-electric submarine generates electricity that drives the motor, which then powers the propellers. There are major disadvantages to this design: a diesel-electric submarine must frequently surface to recharge its batteries, and cannot sustain high speeds for prolonged periods of time.

In the mid-1950s, the U.S. Navy shifted its research and development focus to nuclear propulsion. As with any revolutionary new technology, there were some serious growing pains; it would take a while for the first nuclear-powered boats to consistently exceed the reliability and effectiveness of the latest and most advanced diesel-electric designs. But over the coming decades, it became clear that nuclear propulsion handily outperforms its diesel-electric counterpart across numerous fronts: notably, it offers virtually unlimited range and travels at much higher sustained top speeds despite being markedly quieter. The U.S. Navy quickly began to phase out its fleet of conventional boats in favor of the all-nuclear force submarine force that it currently operates.

For decades, it seemed like a foregone conclusion that the Navy would never again return to conventional propulsion methods—however, recent strides in air-independent propulsion (AIP) technology pose a fresh challenge to what has been the Navy’s ironclad commitment to nuclear propulsion. AIP, in short, is a method of propulsion that allows the submarine to operate without direct access to outside air. There are three main ways that this can be accomplished on modern submarines: closed-cycle steam turbines, the Stirling system, and fuel cell technology. Each of these methods has its own set of benefits and design challenges, but AIP offers a generalizable set of advantages: AIP submarines generate substantially less noise than both their nuclear and diesel-electric counterparts, stay submerged for relatively long periods of time, and are generally much cheaper to produce than nuclear boats. Moreover, many older conventional submarines can fairly easily be retrofitted with AIP systems, giving them a new lease on life.

So, should the Navy revisit conventional submarines on the basis of AIP technology? The two remaining weaknesses of AIP, relatively limited endurance and lower sustained speed are wholly or partially negated in littoral and coastal waters. Though the Navy has historically prioritized the global-power projection capabilities of nuclear submarines, this doesn’t mean that there isn’t room for a small, cheap defense force composed of AIP submarines.

FULL ARTICLE

[ET2SN]

The USN's overall, strategic goal is to keep the hostile waters in someone else's back yard via force projection.

More advanced and quieter nuke propulsion? Sure. They'll look into it.
More advancements in patrol capability (the P8 Poseidon for example)? Defiantly, but think about where most of these US patrol aircraft work (hint, it isn't near our continent).

Diesels (and by extension, AIP) haven't been a US priority since the 1980's and that was mostly due to heritage and basing concerns*. The Navy got over diesel boats a long time ago.

As a former crew member on the USS Barbel (SS 580), trust me, they ain't coming back.



*- Japan had a prohibition against nuclear powered boats being based at their ports at the time. That has since changed.

[U56]

I am not sure the USA was wise to drop out of the diesel/aip niche. There appears to be a lucrative world wide market for submarines, seems like an ever increasing number of navies want them. Look at the success of French, Swedish, German and Russian sales of Scorpenes, Type214s, Kilo's etc., even the Chinese are now getting in on the act. The vast majority of these purchasing countries are unable to afford nuclear submarines. The Australians have even ordered a diesel version of a French nuclear design.
The present difficulties of Taiwan's search for a submarine provider would not presently exist if the US had a modern off the shelf model available.

[ET2SN]

The last time the US tried to sell a diesel boat (I think it was the Blueback), it didn't go so well.

It was one of the countries in South America and rumor had it that the US backed out of the sale the first time the other Navy tried to dive.

There were only a handful of US shipyards that could build a sub and I always got the feeling the Navy liked to keep them on a short leash.

[Cybermat47]

With France, Germany, Australia, and other diesel-electric and AIP users firmly within the USA’s sphere of influence, is there a need for the US to make diesel-electric or AIP submarines? If the US strategy stated by ET2SN works, then future naval conflicts will be fought closer to the waters of the USA’s allies. They’ll need diesel-electric and AIP subs, but the USN won’t.

[Mr Quatro]

They would have to build a new shipyard to build a diesel boat

All of ours are full of new construction or up grades and repairs or other naval vessels.

Something like years behind schedule

but I would like to see it happen for coastal defence after a major war

Keeping the enemy at bay for sure in the Gulf of Mexico and the Gulf of Alaska for just two reasons,
but as we all know any major shipyard would want export the diesel-electric AIP boats and that
would take years, plus permission.

Just hopeful wishing

[U56]

Originally Posted by Cybermat47

With France, Germany, Australia, and other diesel-electric and AIP users firmly within the USA’s sphere of influence, is there a need for the US to make diesel-electric or AIP submarines? If the US strategy stated by ET2SN works, then future naval conflicts will be fought closer to the waters of the USA’s allies. They’ll need diesel-electric and AIP subs, but the USN won’t.

Interesting points, but they are all afraid to sell any to Taiwan for fear of upsetting their business relations with China. Incidentally the French produce the successful Scorpene submarine, it appears purely for export, as I think all French Navy subs are nuclear, as are the UK. The last UK diesels were the 4 sold to Canada. The Canadians seem to have had a lot of trouble with these, but I am not sure that is the fault of the submarine.

[Onkel Neal]

I just don't see a diesel or AIP boat being viable 2000 miles away from port. If they have to stick a snorkel up, then they are not going to remain hidden for long. And if they have to run a diesel....

[ikalugin]

Nuclear is the best air indepdent propulsion when endurance and power output are important.

[les green01]

if you hadnt read the book blind men bluff great book both sides during the cold war surface diesel-electric subs by holding them down when they couldn't charge batteries or draw in air and get rid of the bad air

[Kapitan]

Originally Posted by U56

I am not sure the USA was wise to drop out of the diesel/aip niche. There appears to be a lucrative world wide market for submarines, seems like an ever increasing number of navies want them. Look at the success of French, Swedish, German and Russian sales of Scorpenes, Type214s, Kilo's etc., even the Chinese are now getting in on the act. The vast majority of these purchasing countries are unable to afford nuclear submarines. The Australians have even ordered a diesel version of a French nuclear design.
The present difficulties of Taiwan's search for a submarine provider would not presently exist if the US had a modern off the shelf model available.

There is a lot more to it than that, for a start you cant simply buy an off the self nuclear submarine it is actually illegal to transfer this technology to any state as per the nuclear non proliferation treaty, and I know your going to say but India has done this with a Russian submarine it hasn't, Russia has leased the submarine to India and upon the expiration of the lease it will be returned to Russia

Different countries have vastly different foreign policies, the USN is about global deployment and policing thus the use of AIP or conventional submarines do not fit within this doctrine, there no way an AIP or Conventional could keep pace with a CVBG over an extended period of time.

Of course there is the argument of littoral waters, well why deploy a vessel with limitations when another boat can offer you more than you will ever need and do the job far better? after all if we listen to Gorshkov "Better is the enemy of good enough."

With France, Germany, Australia, and other diesel-electric and AIP users firmly within the USA’s sphere of influence, is there a need for the US to make diesel-electric or AIP submarines? If the US strategy stated by ET2SN works, then future naval conflicts will be fought closer to the waters of the USA’s allies. They’ll need diesel-electric and AIP subs, but the USN won’t.

ET2SN is correct in his statement the USA will be forever haunted by December 7th 1941 and thus will do anything and everything to keep any threat away from their shores, this means in their doctrine there is no requirement for conventional or AIP boats. (same with the UK)

if you hadnt read the book blind men bluff great book both sides during the cold war surface diesel-electric subs by holding them down when they couldn't charge batteries or draw in air and get rid of the bad air

BMB is a good read that is for sure, and there are plenty of instances where conventional submarines have caused embarrassment to their nation or been forced to the surface.
USS Cochino suffered a battery explosion in the Barents sea, USS Gudgeon was surfaced by the soviets, a Zulu V SSB was forced to surface by USS Grenadier, 3 of the 4 foxtrots sent to Cuba in 1962 were surfaced, Canadian Oberon class counter detected by soviet Delta class and forced out of theatre (1981) there's many !

Interesting points, but they are all afraid to sell any to Taiwan for fear of upsetting their business relations with China. Incidentally the French produce the successful Scorpene submarine, it appears purely for export, as I think all French Navy subs are nuclear, as are the UK. The last UK diesels were the 4 sold to Canada. The Canadians seem to have had a lot of trouble with these, but I am not sure that is the fault of the submarine.

Tiawan will be building their own submarines soon, they had bough 4 old Dutch boats, and in the next 10 - 15 years the current Walrus class will likely start being phased out.

The scorpene is designed primarily as an export boat the Marine National will not likely operate them, like the USN and RN the MN has no need for conventional boats.

The last UK conventional the Upholders now the Victoria class have had issues, bear in mind they had sat idle for some time and Canada does defense on the cheap.
Canada refused to refit them in the UK yards before delivery and instead of heading the advice of the UK government to have them transported via heavy lift ship they decided to have them transit under their own power, the result was the death of a submariner in the HMCS Chicotami.
The deal overall was totally in Canadas favor they got the trainer and four boats for $750m CAD plus shipping and were done a lease to buy scheme interest free.

Canada cried foul play but in reality it was Canadas cost cutting and ignorance that ultimately cause their problems. (and I'm speaking as some one who lives in Both countries)

[sdmuleman]

Keep in mind also that a non nuc sub still has to meet all the Subsafe wickets for design, construction, maintenance, etc. That means that it's still going to be very clostly and hard to build, especially needing a new design & testing and certification, and likely standing up a new submarine shipyard to build them. Thus, the cost savings is likely far less than folks think. Yes, manning is lower, and you don't need costly nuclear trained Sailors, but that's again less of a savings than you'd think.

Also, shear physical size is required for certain missions - a small diameter hull isn't big enough to put a big VLS tube on, or embark a drydock shelter, or do certain other missions. Yes, you can shoot torpedos or horizontally launched missiles, but there's many more things out there to do, some of which require a larger boat. Likewise, physical size impact the size of sensors that can be carried. Further, electrical power is also significant - nuc boat not only gives you more or less unlimited propulsion, but also electrical power for fire control systems, sonars, etc etc.

Anyone significant thing to consider is manning, specifically officers. Currently, nuclear training is tightly integrated into the submarine officer (1120) community. You must be nuclear trained and proficient in nuc matters to stand many watches, get promoted, etc. Because of this, non nuc duty would either have to be in addition to regular nuc boat tours (i.e. in place of a shore tour) or would be an off ramp job that more or less takes that officer out of the running for future nuc boat jobs. Given that a diesel boat mission is also inherently less likely to be important, interesting, sexy, etc. it seems very likely that the diesel boats would becomes the second class citizens, with all the baggage and negatively associated. Now, of course other navies do make a mixed navy work, and USN has obviously done so in the past, but there significant differences.

Bottom line, cost/benefit calculus doesn't make sense, and any non nuc construction anytime in the immediate future is highly unlikely IMHO.

[ET2SN]

Originally Posted by sdmuleman

Anyone significant thing to consider is manning, specifically officers.

You've made some very good points, but you also have to consider the enlisted crew. Most of them will have to be specially trained for the class of boat. Its also a much different world when you're under way. Fresh water is much harder to come by if a reactor isn't suppling the power to produce it. That has a huge impact on the crew and their attitude.
"Going caveman" can be fun when you're young, but only for so long. Being a finalist in a "stink off" competition can also result in some skin diseases and even dental issues if water is really being rationed, and its always being rationed.

On the Barbel, the enlisted shower got tagged out (shut off) when we went underway and if you got caught wasting fresh water, that could lead to four or five hours on "still watch" in the engine room (when we ran the stills, the engine room could easily get above 100 degrees/38 degrees C). There was a lot of pride in the crew, but going to a Nuke felt like a luxury and I didn't waste a lot of time crying for the "good old days".

[ET2SN]

Originally Posted by Onkel Neal

I just don't see a diesel or AIP boat being viable 2000 miles away from port. If they have to stick a snorkel up, then they are not going to remain hidden for long. And if they have to run a diesel....

Just something to consider, because a lot of the "conventional wisdom" glosses over it-

A nuclear submarine sounds like a nuclear submarine. It has coolant pumps and steam turbines.

A diesel submarine sounds like any other ship that uses diesels for power, whether or not its running on the snorkel. Its very easy to get lost in the clutter of civilian traffic, even when running on the surface. We turned hiding in plain sight into an art form.

[Kapitan]

Originally Posted by ET2SN

when you're under way. Fresh water is much harder to come by if a reactor isn't suppling the power to produce it. That has a huge impact on the crew and their attitude.
"Going caveman" can be fun when you're young, but only for so long. Being a finalist in a "stink off" competition can also result in some skin diseases and even dental issues if water is really being rationed, and its always being rationed.

Not wrong I spent time on quite a few boats even the nukes and they all have a similar water saving policy, in the RN your limited to a shower lasting no more than 1 minuet of running water, naturally you find ways to maximize its use.