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Report to Congress on Virginia-Class Attack Submarine Program

The following is the July 31, 2017 Congressional Research Service report, Navy Virginia (SSN-774) Class Attack Submarine Procurement: Background and Issues for Congress.

From the report:

The Navy has been procuring Virginia (SSN-774) class nuclear-powered attack submarines (SSNs) since FY1998. The two Virginia-class boats that the Navy has requested for procurement in FY2019 would be the 29th and 30th boats in the class, and the first two to be covered under a multiyear procurement (MYP) contract for at least 10 Virginia-class submarines to be procured in FY2019-FY2023.

The Navy estimates the combined procurement cost of the two Virginia-class boats requested for procurement in FY2019 at $6,502.3 million (i.e., about $6.5 billion). The second of these two boats is to be the first Virginia-class boat built with the Virginia Payload Module (VPM), an additional, 84-foot-long, midbody section equipped with four large-diameter, vertical launch tubes for storing and launching additional Tomahawk missiles or other payloads. The Navy plans to build all Virginia-class boats procured in FY2020 and subsequent years with the VPM, and the Navy’s FY2019 budget submission shows that VPM-equipped Virginia-class boats in FY2020 and beyond have an estimated recurring unit procurement cost of about $3.2 billion in today’s dollars.

The two boats requested for procurement in FY2019 have received an estimated total of $2,128.9 million in prior-year “regular” advance procurement (AP) funding. (This figure is an estimate, because Congress has not yet completed action on the FY2018 Department of Defense appropriations act.) Based on this estimate, the Navy’s proposed FY2019 budget requests the remaining $4,373.4 million in procurement funding needed to complete the boats’ estimated combined procurement cost. The Navy’s proposed FY2019 budget also requests $1,810.9 million in “regular” AP funding for Virginia-class boats to be procured in future fiscal years, and $985.5 million in additional Economic Order Quantity (EOQ) AP funding for components of Virginia-class boats to be procured under the FY2019-FY2023 Virginia-class MYP contract, bringing the total amount of procurement, “regular” AP, and EOQ AP funding requested for the program in FY2019 to $7,169.8 million (i.e., about $7.2 billion), excluding outfitting and postdelivery costs.

The Navy’s force-level goal, released in December 2016, is to achieve and maintain a 355-ship fleet, including 66 SSNs. To increase the size of the SSN force toward the 66-boat goal, the FY2019 30-year shipbuilding plan includes 16 more SSNs than the Navy’s previous (FY2017) 30-year shipbuilding plan. The first of the 16 additional SSNs is a second Virginia-class boat in FY2021. Under the Navy’s FY2019 30-year shipbuilding plan, a 66-boat SSN force would be achieved in FY2048. CRS and CBO estimated in 2017 that adding even more SSNs to the earlier years of the 30-year shipbuilding plan could accelerate the attainment of a 66-boat force to as early as 2037. The Navy’s FY2019 30-year shipbuilding plan shows options for adding another 12 SSNs to the 30-year plan, but only 3 of the 12 occur in the earlier years of the plan.

From the mid-2020s through the early 2030s, the number of SSNs is projected to experience a valley or trough, reaching a minimum of 42 boats (i.e., 24 boats, or about 36%, less than the 66-boat force-level goal) in FY2028. This projected valley is a consequence of having procured a relatively small number of SSNs during the 1990s, in the early years of the post-Cold War era. Some observers are concerned that this projected valley could lead to a period of heightened operational strain for the SSN force, and perhaps a period of weakened conventional deterrence against potential adversaries such as China. The projected SSN valley was first identified by CRS in 1995 and has been discussed in CRS reports and testimony every year since then. As one measure for mitigating this valley, the Navy’s FY2019 budget submission proposes to refuel and extend the service life of one older Los Angeles (SSN-688) class submarine. The Navy states that this could become the first of as many as five Los Angeles-class SSNs to be refueled and have their service lives extended.

via fas.org

  • Curtis Conway

    We need submarines folks, and lots of them.

    • PolicyWonk

      Indeed. Its a shame we didn’t properly plan for what many knew would become a problem.

      But this is partially why I think we need to purchase a fleet of AIP boats, forward basing them in the Med, Persian Gulf, and SCS, to supplement the SSN fleet. Modern SSK’s now have the endurance and flexibility to be incredibly dangerous, as we’ve found out in our own war games, let alone various other events.

      We can purchase 3 SSK/AIP boats for roughly the price of one Virginia: this makes them a bargain.

      • Curtis Conway

        You could write a Masters Thesis on all the treaties about ‘this subject’ written over the last three decades, or since the draw-down after the Berlin Wall fell, considering the advantages of keeping a large Silent Service in force.

        • PolicyWonk

          The surface fleet serves as the deterrent because its highly visible and shows the flag (and therefore our interests) very clearly/bluntly and has done so for decades.

          But the ultimate stealth and sea-going battle/ISR platform is the submarine: everything else is merely a target.

          Diminishment of the SSN fleet is/was no way to save money or preserve the peace.

          • Every now and then a SSGN needs to show up in Busan.

          • PolicyWonk

            Heh – indeed.

            Lamentably, the SSGNs are going to go away, and a lot of firepower and capability will go with them. The Virginia’s with VPM are a step in the right direction, but they cannot replace the Ohio-based SSGNs.

            And it remains to be seen if the Columbia-class boomer production line will be extended to replace the SSGN fleet.

      • DaSaint

        Agree that we need more boats, but as much as AIP has it’s place, it would be very problematic to design and build a new class of AIP-capable SSKs at either EB or NNS. It would severely interrupt their workflow which is humming like a dream right now. And you couldn’t realistically build them at a yard that isn’t conversant with SS construction, so that would limit you to building them overseas, which just ain’t happening.

        But…it wouldn’t prevent you from purchasing a couple used ones for additional ‘training assets’, and position them accordingly. That may fly.

        • Curtis Conway

          DaSaint, I though of you this morning. You might want to review my suggestions on another topic:
          Prioritization and strategy is needed in the Defense Budget.

          Nuclear Deterrence is the highest priority.

          The Silent Service should come next and get the count up.

          Joint EM Spectrum control, protection, exploitation should be next, then let everybody (Joint Chiefs) fight it out in the pecking order.

          Personally I would make sure they get the FFG(X) right, and provide us with what we currently do not possess. A capable low cost Multi-warfare asset that can do most everything, and go most anywhere, even the Arctic, and build a lot of them.

          Then get that 12th NSC paid for, and have a healthy debate about whether ‘that force’ should grow for International Tasking via the plethora of Bilateral agreements & treaties across the planet.

          Then build an AEW&C V/STOVL aircraft to support the Expeditionary Strike Groups (Lightning Carriers).

          Perhaps the USAF consider some F-35s of different flavors for specific mission sets. The “C” birds would buy them a lot, but more (new upgraded) F-15s will do the trick combined with their Quarterbacks (and growing Quarterback Bench) they already have (F-22s & F-35s).

          Systemic improvements should provide/protect basic services, and apply to the greater community regardless of service. Communications, and EW development falls in this area.

          Engine improvements (particularly the [ITEP] turbine upgrades) should move ‘full speed ahead’. Build more plants and make more engines faster. Perhaps a program to increase the range of all M1A Abrams via a new ITEPed engine. The LV100-5 awaits in the wings, and it buys a lot for readiness, range & reliability. Maintenance on the AGT1500 is a bear.

          The FVL program should accelerate the LOACH Approach, and NOT use the V-280 Valor for that specific [attack] mission set. The V-280 Valor is your primary H-60 Replacement, and not for Primary Attack Missions.

          If the HVP development will not provide the solution in a decade or less, then put 8″ guns on DDG-1000 like they should have in the first place. The Navy has been ‘not supporting’ the Marines in NGFS long enough (too long) and lying about future support. The proof is in the pudding, and the Marines need Big Shells hitting the beach now (Today Gentlemen . . . today).

          Get EMALS Fixed! A single Cat Casualty taking out a Bird Farm IS NOT ACCEPTABLE, and whoever made, or supported, that decision to do otherwise should be removed from the equation. THAT was fundamentally a HUGE Mistake. An additional 100 tons on a 100,000 ton vessel is an easy decision given the capabilities of that platform. The alternative is NOT ACCEPTABLE.

          Get those Icebreakers going, and I suggest just build 6 Heavy. Every iteration will be less expensive than the previous, and the cost break by the fourth (4) unit will be a very compelling ‘argument for’ given development of an additional [new] design. That vessel will be a floating command center, so greater aviation support/operations, and don’t forget about the Armory for the MARDET for when they are present. These will be multi-mission ships, not just Icebreakers, and you have to protect THAT asset just like you have to protect LCC-19/20, particularly in the Arctic during times of tension, and those times will come. If the NSC force should grow . . . well, we will now have a lower tension response to international problems, instead of just sending in the Military. I’d rather have a Sheriff Deputy on station, than the Marines. If the Marines are needed, they will not be far away, and command and control is already on station. I would like to see the NSC force grow to at least 14 units and have them support International Maritime Operations Centers (IMOCs) in the South China Sea, the Mediterranean AOR, and perhaps the Baltic.

          • DaSaint

            Curtis, you have entirely too much time on your hands my friend! Just kidding. Your points are well thought out and articulated. Let me see if I can respond to some of them, though not all:

            Agree with the 6 Heavy Polar Icebreakers. Make them SOF capable with significant aviation (read 2 helo) capabilities and Command & Control capabilities.

            Build the most capable FFG possible at the most affordable price possible for 30 units. Split production amongst 2 yards and compete production lots after the first 4 units. For my money, that’s the Type 26 or the Navantia F-100, not the FREMM.

            Build 3 SSN’s every year. One to each yard, and the third competitive. Every year until we have the subsurface levels we need.

            Now let me digress to some other points:

            Ensure that EVERY SSN is equipped with at least 12 Harpoon missiles as soon as possible. They’re going to be fighting more surface ships than subs in the Pacific, but will still retain a capable loadout of ADCAPS for the subsurface and surface threats

            Equip EVERY DDG and CG with 2 CIWS. Either 2 Phalanx or 1 Phalanx and 1 SeaRAM TODAY. No and, if or buts about it. I can’t stand to see a Burke with a missing CIWS up forward.

            Equip EVERY auxiliary with 2 Phalanx.

            Equip EVERY H-60 bird with a credible air-to-surface missile, and provision every CG, DDG, LCS, and pending FFG with an appropriate quantity of such ASM. And I don’t mean 4 rounds. More like 12.

            Ensure that EVERY CG, DDG, and FFG has at least 24 VL ESSM to complement whatever other SAM loadout they’re carrying.

            Put a platoon of Marines on every LCS. Permanently. You want to fight in the littorals, then you need Marines on board. Shoot, I don’t mind if they’re occasionally stationed on DDGs for particular rotations.

            Just some thoughts to increase near term lethality, defensive capability, and long term viability.

          • Curtis Conway

            What do you think about increased Proactive Coast Guard tasking with a greater NSC fleet…?

            How about that V/STOVL AEW&C aircraft for the ESGs and the MAGTF…?

            I know your not going for the new engine on the Abrams Tank.

          • DaSaint

            I promised not to comment on every item, but not because I didn’t agree. Ok, here goes:
            I believe there should be 12 NSC. Shoot, if manning wasn’t an issue, I’d say 16.
            An AEW version of the Osprey with fixed phased arrays kinda makes sense on multiple levels. The technology is there, just not sure if the Osprey has the altitude capability to make it effective, plus it’s unpressurized. Can it be pressurized? That would help.
            The Abrams tank should have been reengined long ago. But this is a maritime forum, so…:-)

            Be well my friend!

          • Curtis Conway

            “I can’t stand to see a Burke with a missing CIWS up forward.”

            This was done by a mindset that wants the ship to be safe while it runs, not attacks. Interesting mindset, HUHH.

            When the Israeli Merkava Tank was first fabricated they saved on metal for the rear escape hatch by making them of plywood. The first stations for Merkavas was on the Golan in defensive positions. They were to fight to the death, and some did . . . but NONE turned to run away!

          • Rocco

            Curtis does have to much time on his hands!! Lol that’s because he’s retired!! Great ideas between the both of you however we don’t have enough infrastructure to do all that yesterday!!!

          • Rocco

            Curtis as usual you hit the proverbial nail on the head!! With a pneumatic hammer!!

        • Curtis Conway

          The East Bank at HII Pascagoula is starting to hum. Bremerton still has some room/capacity. How about Long Beach Ship Yard? If you wanted to start a new jobs program we could go to Oakland (I don’t want to go though).

          • Not the same work force that built Sturgeons in the ’70s. Let’s hope that they’re better. Belay that – let’s make them better! MAGA baby!

      • Rocco

        Agreed. BTW the knew this would happen they just didn’t want to deal with it.

      • Charlie

        It was Clinton cancelled the contracts so his buddies could build aircraft carriers

        • Rocco

          Which we needed!! Or we’d have 6 carriers now!!

        • PolicyWonk

          The Clintons, in all fairness to them (um… this isn’t an easy one to say) didn’t know much about the military (and said so). They followed the military draw-down plans left behind by his predecessor, George H. W. Bush (his Sec Def was Colin Powell, who drew up the plans), due to the so-called “peace dividend”.

          They eventually realized the original plans went too far, and subsequently increased the budgets. Both Clintons eventually became well educated w/r/t military matters, especially Mrs. Clinton, who earned the respect of many in the Pentagon during her stint as a US Senator, and was even considered for Sec Def (Ray Mabus got the job, and I don’t know that he has many fans on this forum if memory serves).

      • NavySubNuke

        If you want a hollow submarine force that provides numbers but no actual capability increase to the fleet — and worse actually harms the fleet by diverting necessary resources and personnel away from the SSN force —- then by all means lets buy some SSKs. If you want imagine what this future looks like – just look at what LCS is providing to the fleet….

    • pismopal

      Yep…boomers keep them up at night and there is no current way of countering them.

    • NOW HEAR THIS! Pay attention and listen to Curtis, he knows that of which he speaks!
      (And 5 more up clicks).

  • NavySubNuke

    Good luck to the entire PMS-450 team and their contractors as we work to get VPM built and into the fleet as quickly as possible.
    As we get ready to retire the SSGNs those extra tubes are going to be play a key role in continuing to deter conflict. And should deterrence fail they will be essential to winning the fight.

    • DaSaint

      Completely agree!

  • Nick

    As is well known money grows on trees, have to plant a lot more to fund the additional $50B to $55B for the additional 16 SSNs. It would be more realistic buy a new very quiet new generation conventional sub class for ~ $0.8M each, for 32 total twice the number for half the cost ~ $26B, besides the current build of two SSNs per year. It will be difficult as there are only two nuclear shipyards, EB and NN, and who will stretched as they will be building the new $122B class of 12 Columbia SSBNs as well. ” Quantity has a quality all its own”.

    • DaSaint

      Buy from whom? We can’t have combatants built in foreign yards. And I concur that EB and NNS don’t have the bandwidth.

  • Leatherstocking

    The lead-in says the 31 Jul 2017 report when it is the 31 July 2018 report. Yup, we’ll be in a real hole in the late 2020s and there’s little we can do to backfill this.

  • SierraSierraQuebec

    There is a route to sufficient numbers of attack submarines, but first it is necessary to exclude some options and set these matters aside in the decision making process. This route would be resistant to even a future hostile presidency and deep cuts to defense below the 3% level and avoid the low numbers of boats in the late 2020’s and the danger to the strategic balance that would create. Democracies must be stronger than dictatorships because the latter have greater freedom to plan and execute despite the throttling of their populations’ potential. Hard charging presidencies, despite the flaws, exxagerated or not, come only once every 3 to 5 administrations, expect the mediocrity and emasculation of various shades and colors of population control socialist engineering to return until the 2040’s and a continuing decline in defense budgets while the dictatorships continue to play the long game.
    Swedish and Japanese AIP submarines use a rather small set of 2 or 4 Kockums V4-275R Stirling heat pump engines of the same basic design to the 1985 trial unit on board the former submarine Nacken to generate a very minimal 150 or 300 kilowatts of power (approx. 200 or 400 shp), which is a bare minimum to propel the boat or energize its systems. Since speed is a square root function of power, its possible to move at low speeds with negligible power, although its not entirely clear if the batteries are being tapped to run the auxilliary mechanicals, HVAC, electronics, and other mundane but essential systems on the boats, as well as driving the boats at 5 and 6.5 knots, respectively, on their small 1600t and 4200t hulls. These vessels are primarily diesel-electric submarines by design, not true AIP boats, and their diesels have around ten times the power level of the AIP powerplant. Ironically, nuclear submarines typically have emergency backup diesels that are larger than the Stirling plants in service today as well as some emergency batteries.

    • SierraSierraQuebec

      The Kockums V4-275R powerplant is little bigger than a small truck engine in size, and although it is vibration and noise free in operation and exports its pressurized exhaust gases offboard while submerged, a number of issues would emerge in scaling up the powerplant in to the thousands and tens of thousands of shaft horsepower as would be required in a true AIP attack submarine. The biggest issue is the quantity of liquid oxygen required to make the bigger powerplant useful, since any carbon combustion system requires a high quantity of oxidant relative to the power output; low to intermediate cruise speeds would be practical, but moving at speeds of 20 to 32 knots would consume the liquid oxygen supply that can not be easily replaced at 16 to 64 times and 10 to 40 times, respectively, over the rate of the slow creeping speed, and this does not even factor in more exponential displacement growth for the bigger engines little less the LOX supply, not a whole lot of improvement over lead-acid batteries. The Japanese are looking at lithium polymer batteries to give that surge of power for tactical speeds up to the 20-30 knot range, but as a guesstimate here this probably will not maintain these speeds for roughly more than 4-12 hours and would require running the normal diesels to recharge the batteries; its an improvement in as far as total energy and speed is concerned, but not by much. Liquid oxygen is as volatile as liquid hydrogen and can explode like on the Hindenberg and Challenger, and it would be not be possible to refuel the oxygen at sea due to the obvious safety hazard of it. It would be dependent on a dedicated tender or port facility for its LOX. Moreover, a large Stirling powerplant would be expelling far more hydrocarbon residues into the seawater, which speculatively could render the boats detectable by the large slow dispersing wake plume akin to a weak oil slick. In conclusion, Stirling propulsion is viable on the current or moderately expanded scale if the result of an effective equal to a hybrid pickup with a lawn mower engine is acceptable as is the case with submarines whose patrol area starts at the mouth of the harbor, but it will not by itself get a boat to a true AIP fleet submarine level. Not surprisingly, no serious growth of this propulsion system has or is under development.
      Hydrogen-oxygen fuel celled boats also can go ‘boom’, and are as much the result of the wishful thinking of ideologically motivated activists and opportunists of the political-industrial complex, the same people whom despite tens of billions in supercomputers and complex modelling give us forecasts so poor that you can’t plan to work on the car more than twelve hours in advance (assuming the opposite usually works more often than not). If you want no direct carbon emissions, a nuclear battery and chemical battery tandem makes more sense, but that would be using the other n word and politically correct fascists would never allow that to happen.

      • SierraSierraQuebec

        There was a brief time ten years or so ago when aluminum-air fuel cells where considered as an alternative to the relatively pricey lithium batteries used in notebooks and the rapidly evolving cell phone market. These fuel cells have close to an order of magnitude more power density, and moreover, as a power supply for automotive/mechanical use they are in the same range as carbon fuel powered engines. The most apparent drawback is they are effectively a solid fuel like coal or wood with discrete units of power production. As an electronics power source they would require constant management to use up the power of a given cell and then replace it outright, which by practical implication also would often require two or more cells. Lithium cells are vastly more convenient given the dozen or more electrical/USB recharging sources in a typical residence, and is essentially akin to liquid and gas fuels in terms of pour in ease of replenishment. Electronic devices have also become vastly more energy efficient in subsequent years, making the lithium battery more practical as a power source. As a mechanical energy source Al-Air cells have the same problem of practical difficulty with replenishing them, which is why aluminum-air powered cars never caught on despite being competitive with carbon fuel powered vehicles and far superior to all battery powered vehicles despite essentially being an all electric vehicle as well. In conclusion, the commercial failure of aluminum fuel cells has been the result of their solid fuel character trying to compete with the preferred convenience and simplicity of effective flexible level pour in or connected energy sources. All novel energy systems are slow to take hold, because the average person has minimal comprehension of them and will always choose the easiest path, hence the current dominance of hydrocarbon liquids and gases, electricity, and rechargeable batteries.

        • SierraSierraQuebec

          The Al-Air fuel cell makes maximum use of the oxygen molecules supplied to it, so that in a sufficiently large enough vessel it would not be necessary to carry oxygen in liquid or any other expensive or unstable form. Air, or more specifically, oxygen enriched air like the range of gases used in deep sea diving would provide a generous supply of oxidant for the fuel. While submerged at depth sending up an air line with a plastic head and some garbage item attached to disguise it amongst a billion other pieces of flotsam in the oceans will readily allow the oxygen to be topped up during brief static silent listening intervals with no real chance of detection. Carrying a surplus of aluminum (energy), perhaps six times as much as the air supply, for propulsion, ship service, and air replenishment would not be a problem in an 8000t vessel, aluminum is one of the most electropositive and energetic elemental metals in existence, but also is stable and has no real storage requirements. The supply of oxygen enriched air would be quite effective at quietly eroding-burning holes or score lines in Arctic ice. The spent electrolyte could be rejuvenated through cold precipitation or filtering out the aluminum oxide, and/or replaced outright as a liquid (corrosive but not volatile). The boats could be replenished at sea or suitable anchorages since the fuel bars, fresh electrolyte, and oxygen enriched air or the electricity to compress more could be achieved with modest additions on many logistical ships; a dedicated conveyor system for the aluminum fuel bars presents a slightly lesser challenge than munition replenishment equipments since the aluminum is neither fragile, explosive, nor combustible, not that its range would require out of port replenishment except in rare circumstances. The boats would gain ~650t in displacement during a patrol due to oxygen fixation, which would have to be adjusted for by one means or another.

          • SierraSierraQuebec

            Al-Air fuel cells applied to a Virginia class submarine hull (realistic numbers, not theoretical maximums):

            30MW at 200W/kg = 150 metric tons, at 1300 W-h/kg = 8.7 hours at 35 knots and 303nm
            -or- 46.5 hours at 5.6MW and 20 knots & 930nm
            -or- 15.5 days at 0.7MW and 10 knots & 3720nm
            (assuming published/probable figures for Virginia class boats are reasonably true)
            900 metric tons of aluminum provides energy for a patrol range of
            approximately 22,000nm at 10 knots (not including air compression, ship
            service, and other energy allocations), consistent with the range of
            large diesel-electric boats.

            Oxygen Required:
            133.5 metric tons at 0.75323 m3 per kg = 100,556 m3 at 1 atm or 101,888 m3 at 1 bar
            at 482.63 bar (7000psi titanium tanks) at 210.99 m3 -or- 4 x 2.2m diameter cylinders 13.9m long (46ft) each
            at 344.74 bar (5000psi steel tanks) at 295.55 m3 -or- 4 x 2.2m diameter cylinders 19.4m long (64ft) each
            at 206.84 bar (3000psi aluminum tanks) at 369.44 m3 -or- 4 x 2.2m diameter cylinders 24.3m long (80ft) each

          • SierraSierraQuebec

            The dimensions here were chosen just to provide a mental image of relative size of the oxygen-air tanks; at 2.2m they would be the same diameter as the four Virginia Payload Module Tubes and turned horizontally even the aluminum tanks would be a little less than the 84 feet or 25.6m many sources quote as the length of the inserted hull section. Although the VPM’s are not used to store pressurized air, they are of substantial strength that have to withstand sea pressure down to it least some depth from the surface as well as launch stresses. It should be clear that fitting such tanks in the former reactor and steam turbine section would not present a space or weight problem in a Block IV 30MW-AIP boat. The actual tanks would be the optimal spherical form widely used to store liquidified gases in tanker ships, space rockets, and industrial storage depots, and could be constructed from aluminum, steel, or titanium depending on the outcome of a correlated engineering analysis of option variables that I do not have the time to revisit after so many years from a smaller version of this boat type, have no off hand knowledge and/or engineering experience in every discipline to make quick estimates from, and little comparable known data to extrapolate from, but to offer an estimate here the tanks would weigh in the region of 500 metric tons to store 133 metric tons of compressed oxygen in 5000 psi steel tanks, but once again this is not a reliable figure. (Scuba tanks often carry 1 pound of gas for every 4-6 pounds of total weight to offer a quick comparison to a small cylindrical tank). These or the other metal tanks would not have to be inside the pressure hull, saving the weight of enclosing them and the potential pressure and fire hazards of OEA leakage inside the manned spaces, but there would be some negative compromise in attempting to blend spherical tanks and a cylindrical pressure hull and might force a radical re-arrangement to put the tanks fore and aft the pressure hull that would result in large re-design costs in the process.

          • SierraSierraQuebec

            The submarines would leave port with a load of pure compressed oxygen, regularly stopping and topping up the pressure with air whenever convenient and subsequently diffusing out the unwanted nitrogen and other gases through slow but relatively efficient diffusion membrane processes possible related to those used to create nitrox and other oxygen enriched airs for (human) diving tanks while the boat resumes being underway. Air could be obtained at depth with an air line and head disguised as one of the billions of similar pieces of floating garbage in the ocean. Over the course of a patrol the oxygen concentration may drop continuously, but it is unlikely the boat would have to stop for a prolonged period of time just to generate enough oxygen for immediate tactical demands and may have other pressing replenishment needs by that point regardless. On return to port or link up with a replenishment ship, the tanks would be emptied in whole or in part for replacement with pure or enriched oxygen-air, although replenishment at sea might require calm or sheltered conditions and only involve partial enrichment. There are a number of hazards and precautions surrounding the use of oxygen enriched air, but they are widely known in the naval and general diving community, so there is a wealth of knowledge and expertise to draw from to arrive at optimal design and best operational practices.
            There is a lot more to be considered with the boats, but suffice it to say, the numbers are in the range.

          • SierraSierraQuebec

            Average Use Ohio SSGN class Cruise Missiles over 30 Year Extrapolated Lifespan: 300 + 100 (Contingency) = 400 Missiles
            [USS Florida SSGN-728, 93 Missiles Launched, Libya, 2011; 4 SSGN in service approx. 10 Years, 616/640 Missiles Total]

            Replacement: 10 Block V Virginia class w/Payload Modules, (28 VPM + 12 VPT) x 10 Boats = 400 Missiles (plus internals)
            Cost: Projected at $3.2B per boat, or $32B for Block V
            Note: Half a billion seems a lot for 4 extra silos & 28 cruise missiles, but this is the published claim and the basis for comparison here; the extra cost apparently reflects growth potential with the VPM’s and/or undisclosed enhancements.

            Alternative: 8 Block V Virginia class w/Payload Modules, (28 VPM + 12 VPT) x 10 Boats = 320 Missiles (plus internals)
            Cost: Projected at $3.2B per boat, or $25.6B for Block V; forward VPT replaced by canted VPM tubes, providing 48 uniform silos for 144 future larger supersonic/hypersonic missiles or initially 16 extra cruise missiles with 64 more internal (ie. 400 missiles on 8 boats) for a few hundred tons & negligible cost.
            Reloadable with 640 preserved missiles from Ohio class SSGN’s. Other options possible at higher cost.
            Additional: 4 Block IV-AIP (Al-Air Fuel Cell Replacement Section), 25-28 Internal Weapons x 4 Boats = ~32-40 Missiles
            Cost: Projected at $1.4B per boat, $800M or more in design costs (fuel cell units, air tanks, motor, distribution, arrangement; much of it already developed for DDG-1000 & other electric drive systems)

          • SierraSierraQuebec

            To mark fifty years of sovreignty abrogation north of the border, the Block IV-AIP boats could be named USS Hecla, Fury, Terror, And Erebus, rather than state or naval servicemen names, potentially waking up a lot of morally arrogant and adolescent people in the process. FONOPS through the Northwest Passage coud be regularly announced and exercised as part of a normal work up patrol for them. Cool names for a small trial sub-class of submarines too.
            A smaller nuclear boat will not save any money. The Virginia already is a cost effective size range for a nuclear submarine, employing a smaller reactor like the older S5W 11MW unit to modern lifetime core standards would require some billions to do and result in a third of the power and the loss of any hoped for cost savings of then two smaller classes of nuclear submarines. The Los Angeles class S6G at 26MW and Seawolf class S6W at 34MW are in the same power range as the lifetime cored 30MW S9G of the Virginia class, so the cheapest and fastest route would be to use the S9G reactor at lower power levels and accept a modest increase in expected lifespan by five or ten years and/or freedom to cruise at higher average speeds. To get the boat down to 5000t or less would require gutting it and accepting greatly reduced combat effectiveness in whatever you could squeeze in to it for a price tag of around $2.2-2.4B with fewer than 18 weapons on board. A simplified Virginia that omits the forward VLS would cost halfway in between at $2.5-2.6B, the cost savings allowing twice as many installed cruise missiles on destroyers or an arsenal bomber.

          • SierraSierraQuebec

            Modern torpedos are virtual underwater missiles that have reaction engine power to weight ratios high enough to fly, and it is not infeasible to mount jettisonable wings, control fins, aerofans, and a rocket booster on a Mk48 sized torpedo technology base; since (shallow) water creates about ten times the resistance compared to air, the weapon nominally would fly ten times faster and farther, making it a viable successor to the long retired nuclear SubRoc and the anti-ship equal to two or more cruise missiles, but this would not save much displacement on a smaller nuclear submarine and you would have to fund and engineer this torpedo that could experience a lot of technical problems in development given its lack of precedent and multi-stage flight profile.
            The AIP submarine could evolve in to an even better boat as selected technologies and engineering mature. There has been some research in artificial gills to extract oxygen from seawater as like all sea life does on lower energy scale, here you would have a significant economic application to develop the technology further. Other oxygen sources could include compounds like ferrous oxide (rust) from the classic thermite reaction that can melt holes clear through an engine block with the aluminum reductant, even though no developed system exists at present; a conductive molecular porous membrane and suitable electrolytes or other approaches would be inexpensive and easy to employ if it worked well. The Al-Air fuel cells would require little to no local control and could be mounted outside the primary pressure hull much like external weapons, freeing up the extra weight for a smaller, deeper diving manned pressure hull capable of descending below the thermocline as deep as 1000m. The Al-Air fuel cells also could be arrayed around the primary pressure hull, resulting in protection from lightweight ASW torpedos.

          • SierraSierraQuebec

            The foreplanes, sail, and rudder generate more than 15% of the underwater resistance, folding masts, casing stowed deepwater air intake and communications lines, a collapsing conning tower, and a networked series of strong thruster valves connected to the network arrays of fuel cells would provide redundant, power efficient, active helm control that would be particularly effective at low speeds when the planes lack flow to be effective. The net effect of these alterations in a purposely designed AIP boat some years in the future would be a 5000t ship running on 20MW of propulsive power that would be even quieter and longer ranged than the AIP Virginia boat. This submarine could come in at under a billion and have manning and operating costs lower than smaller diesel-electric boats given that most of the machinery is simple in operation and amenable to remote operation.
            The Al-Air fuel cell submarine was viable back in the 1980’s when modelling and mathematical analysis demonstrated a potent boat was technologically possible, with over thirty years of intervening developments that prospect has not changed because fundamental chemistry has not changed either. If future naval operations are to be assured, it is critical to develop sensor dominance much like the radio and radar dominance that quashed the U-Boat threat, particularly at present acoustic dominance in the effort to counter area denial from adversarial submarine forces. This will require hunter drones with active transducers and towed arrays capable of keeping pace for periods of time with fast naval forces or operating separately for longer periods at slower speeds in order to achieve some degree of acoustic sensing saturation. All weather drone seaboats could efficiently accomplish the bulk of this sensor fleet, but underwater drones also will be needed in numbers when air control is not present and will require a propulsion power source for which there are no realistic alternatives other than aluminum, since even a narrow torpedo like design and light towed array will require significantly more propulsion energy for size than a vessel hundreds of times larger. This massive sensor net would be bound together for analysis by artificial intelligence to extract every possible piece of useful information out of it.

          • SierraSierraQuebec

            The suggested route is to build the four trial boats in the near future, apply lessons learned, and start work on the design and construction of optimized Al-Air submarines so that they start commissioning in numbers at the 2028 low point in the submarine fleet so that the ebb is as brief as possible and not likely to have any effect in the longer range strategic balance. Attempting to build up a nuclear submarine only force in numbers will never get funded in the long run nor can the building expertise be expanded very easily even with the funding, but little prevents the continued existence of a few dozen nuclear boats and their ability to run at speed over global ranges and quickly generate the local superiority in force essential in most military operations. Its time to start understanding what economy of force means and start paring away non essential excess.