Monday, September 2, 2019

Common Support Ship

The military has been pursuing commonality and modularity for some time, now, and with generally dismal results.  In particular, the military has been fascinated with the idea of common platforms that can be modified to serve multiple functions.

The Army has attempted to create a common vehicle, both armored and non, from which families of specialized vehicles can be created.  The Stryker and Bradley have both been used as the basis for multiple, specialized vehicles with some degree of success.

The various aviation services have attempted to create common airframes.  The F-35 is an example of such an attempt.  The S-3 Viking, though not an intentional attempt at a common airframe, did develop into ASW, SigInt, Tanker, and COD airframes.

The Navy attempted to create a base LCS that could morph into specialized functions via swappable modules – a disaster on every level.  The Navy also appears to be attempting to use the San Antonia LPD as a common hull, necking down various amphibious ship types, replacing older LPDs and LSD-41/49s.  It has also been proposed as a dedicated ballistic missile defense ship.

And so on.

Most attempts at a common base have met with limited success for a variety of reasons.  Ironically, the example of the unintended common airframe of the S-3 Viking has, arguably, met with the greatest success.

Along the lines of a common airframe, one could imagine a common hull for a range of support ships.  A reader offered this idea in a comment in a previous post and suggested uses such as mobile HQ's, hospital ships, mother ships, ammunition haulers, artillery/rocket platforms, and repair shops. (1)

ComNavOps has stated repeatedly that modularity is, by definition, a sub-optimal solution – a failure, in essence.  So, why would a common hull be a good idea?  The difference is the application.  Commonality and modularity are failures for combat platforms because, as I said, they inherently produce sub-optimal platforms and sub-optimal platforms will lose to optimized platforms every time.  On the other hand, for non-combat applications, like a family of support ships, the fact that they aren’t exquisitely optimized really doesn’t matter.  A little inefficiency in a support role is perfectly acceptable.

What we’re talking about with a common hull is, basically, a WWII Liberty ship.  A fairly generic ship that can be quickly and cheaply produced and can, with minimal modifications, serve a variety of functions.

The danger in trying to adopt a common support hull is making it too all-encompassing.  The hull size required to support an EOD MCM unit is much smaller than that required for hospital ship.  If one sizes the common hull for the largest possible application then all the lesser applications wind up with a ship that is too big and, as a consequence, overpriced.  Thus, for a common support hull to work we have to limit the applications to those that share a reasonably similar area (square) and volumetric (cube) need.

Here’s a list of possible functions that could be accomplished with a common hull and the required vessel size.

mobile HQ's – small
repair vessel - small

tender - medium
artillery/rocket platforms – medium
MCM mother ship – medium

troop transport - large
hospital ships - large
ammunition haulers – large

We see, then, that we need three different size ‘common’ vessels to meet our family of needs.  To stretch our Liberty ship example, we would need three different size Liberty vessels.  They could share common characteristics (length to beam ratio, etc.), I suppose, but at some point you’ve got to face the fact that you’ve designed a different ship for each vessel group size.  There’s nothing wrong with that.  Having three ‘classes’ of common ship would be fine.  It might even be possible to condense the three sizes into two without imposing too much waste and inefficiency.  I’ll leave that up to the designers.

The larger point is that there’s a fine line between commonality cost savings and operational inefficiencies due to the non-optimized commonality.  For example, in our medium size group, an MCM mothership would likely need a radically different stern structure for unmanned vehicle launches, small boat launches, etc. than a tender or artillery/rocket platform ship.  Yes, you can take the common medium hull and greatly modify it to fit the MCM mothership requirements but after you do, you’ve probably lost any cost savings that came from the original commonality.  Is it worth it or is it better to just design a different, optimized mothership?  I’m not offering an answer to that, just illustrating the challenge of assessing the balance between commonality and optimization.

So, there is certainly some potential for a common support hull – or maybe two or three common support hull sizes – but we need to assess and balance the potential commonality cost savings against the non-optimized operational inefficiencies.


(1)Navy Matters, “LST Development and Death”, 25-Mar-2019, comment: Seal Of Lion, March 25, 2019 at 8:03 PM,


  1. Why not follow the example of the S-3?
    Build a ship with one task, for example hospital. When we have a good, or great, hospital ship sit down and look what more could be done. Let the design evolve with ease. My guess is that it would be easy to evolve the design into a troop carrier.
    Munition handler might work but that would of course be another study to verify it is a better solution the a new hull. Reuse as much as possible of the sub-equipment, for example the bridge and electronics but no more, don´t reuse for the sake of it.
    F15 had the same development cycle, First a dedicated fighter, then when the design was mature it evolve into the Strike Eagle.

  2. As modularity and commonality have been frequent recurring themes of discussion, Ive noticed a few things. First, warships seem to realize minimal or no cost savings due to serial production(caused by continual design changes?? Overall complexity??), but simpler ships (USNS/MSC) seem to. Second, even if common-hull designs just cant be made to work, there should be more system commonality, which would have a great impact overall. For example, there are supply ships, as well as amphib ships that use diesel power. Exactly why that is, i dont know. But it seems to me that gas turbine power across the board would streamline fuel logistics, as well as personnel training, maintenance, and parts supply.
    Certainly, with the volume of a supply ship, the potential to create a tender is there, the only major needed change being more electrical generation for the workshops. Creating a troopship, a fairly simple exercise. And while quite large, the prepositioning Ro/Ro ships, have vast potential as a basis for design spin-offs.

    1. "But it seems to me that gas turbine power across the board would streamline fuel logistics, as well as personnel training, maintenance, and parts supply."

      I agree but it could come at a significant cost. It really depends of the mission profile and size of the ship. Most cargo is transported at slower speeds than a battle group (Henry J. Kaiser class 20 knots, John Lewis class 20 knots). Turbines are not as efficient at partial load and the available turbines are of a limited size range. There is a wider range of available diesel engines to fit the ships required power.
      The cost of the fuel is not insignificant. Save a million dollars on fuel and you can spend it on war fighting.
      Commonality is good up to the point it hinders your ability to complete the mission.

      Article about commercial use of turbines that discusses some of the issues with turbines in ships.
      Quote from the article. "The specific fuel consumption of a gas turbine at 33% power or less may be two to three times that at full power."

      Article about fuel costs in shipping.

  3. something akin to a support version MEKO design with plug in play hull, propulsion and sensor and weapons suites. Damen shipyards kind of do this now, they have a whole host of civil ship and military ship designs with commonality of hull ect.

  4. Combidock. Use large, prebuilt modular sections to change configurations, and/or use standard ISO containers. Google Think Defence Blog Forman exhaustive look.

  5. I think that this is another situation where the navy needs BuShips.

    I did a paper for my history degree contrasting the WW2 experience of two shipyards, Cramp in Philadelphia and Manitowoc in Wisconsin, who both were contracted to build Gato/Balao class submarines.

    I can't imagine how these efforts could have been successful without BuShips.

    In regards to the situation in the posting, BuShips seems to be a logical starting place.

    They start controlling the development of ships and they could make expert decisions on whether or not a particular hull could be used for a different application, modified slightly, or a new one designed altogether.

  6. Had a idea like this once. Basically the navy could build one common hull that could be refit to do everything from haul cargo to act as a arsenal ship. Basically say have a Stout but cheapish hull based around a common cargo area at the fore and aft of the vessels.

    You could have a series of say 5 in a fleet. Set the up to tie in with say a Burke, Tico, etc these could be fitted to carry loads of Missiles for the fleet to use while also carrying supplies aft or say have a couple set up to operate 2 seahawks or their equivalent for sub hunting etc.

    Heck a lot cheaper to use that set up to hunt pirates or smugglers in the ocean or along our coast.

    1. There's nothing wrong with your idea, conceptually. In fact, I more or less suggested something along those lines in the post. However, be careful that you aren't glossing over some of the practical challenges in a one-size-fits-all-functions vessel.

      For example, your suggestion about operating a couple of helos … It sounds easy and straightforward but there's a lot that goes into it. You'd need to add a flight control station, flight control radar, ?RAST?, hangar space, weapons magazines, fueling station(s), fuel storage, spare parts storage, maintenance facilities, overhead cranes of some sort, enhanced communications, berthing for dozens of helo det crew, and on and on. It can be done, certainly, but it's a bit more involved than just slapping on a flat surface and calling it a day.

      Similarly, 'loads of missiles' require computer interfaces, utility interfaces, exhaust routing, enhanced comms to receive targeting data, diagnostic computers, high temp resistance materials, blast/deflection armor, and on and on.

      Common hulls work well for generic, simple functions but the concept begins to break down as the functions increase in complexity. Helos and missiles are examples of fairly complex functions. Cargo storage/hauling, in contrast, is simple and basic and lends itself to a common hull.

      The key is the degree to which the ship has to be integrated with the mission package. Minimal integration (like cargo) lends itself to common hulls. Complex integration (like helos and missiles) negate any common hull cost savings.

      So, by all means, envision common hull applications but carefully think through the requirements.

    2. To add a bit to this, @James you may want to look at KA Bunga Mas Lima, a container ship which the Royal Malaysian Navy purchased and modified to serve as a support ship with the installation of a helo hangar, flight deck, and RHIB deployment facilities. On one hand, TLDM got themselves a reasonably cheap-ish ship to serve as a mothership for counterpiracy missions in the Gulf of Aden, and some support ship is better than no support ship at all, since the whole point of BM5 and sister shim BM6 was to stand in for TLDM's support ships which were all in refit and unavailable for deployment. On the other hand, BM5 has limitations on what it can do because these were modifications to a container hull, not a purpose built ship.

      But, well, this is what Malaysia could afford, so this is what Malaysia got. The US doesn't operate under the same industrial and economic constraints.

    3. "Similarly, 'loads of missiles' require computer interfaces, utility interfaces, exhaust routing, enhanced comms to receive targeting data, diagnostic computers, high temp resistance materials, blast/deflection armor, and on and on."

      @ComNavOps: Might we be looking at an ammo tender, instead of a missile barge? I recall CSBA's future force assessment from 2016; the idea was to make like Ulithi in WW2 and have the Expeditionary Sea Base ships act as ammo tenders and repair ships.

      Your mileage may vary as to how effective that may be; I have no strong opinions on that one way or another.

  7. I say, for non fighting tasks (oilers, solid stores, repair, Hospital ships etc) just use a commercial design with minimum alterations, eg basic navy comms, basic close in weapons. I know "re-supply at sea" kit is navy unique. These can be produced at a slow rate ny non navy yards and a tender basis. After 15 years scrap / sell / giveaway as they are cheap and not made to last. Times of high tension ramp up production and don't scrap etc. You can argue a helicopter landing pad is useful for deliveries of personnel, medivacs etc, but I don't see this as a big cost driver.

    I'm personally not convinced the saving for common ships is worth all the down sides.

    1. "a helicopter landing pad is useful ... but I don't see this as a big cost driver."

      If you literally mean just a pad, a flat area of deck space, then, yes, it's not a huge cost factor. If, however, you mean a hangar, refueling capability, fuel storage tanks, munitions magazines, and on and on then it's a major cost factor. Most people of casually mention a 'landing pad' really mean hangar and all the rest that goes with it.

  8. No just the pad. It may need to be like some oil survey ships (which don't look that "sexy"), but it does the job.

    1. It really depends on what you want to do with those ships and how you envision them being used. For the Malaysians, they modified Bunga Mas 5 and Bunga Mas 6 with helo hangars because their other support ships they were using for counterpiracy (one of them a Newport News-class LST) had only landing pads, and the problem with that is that the helo is exposed to the elements in bad weather, and you can't do maintennance on the helo. That may or may not work out for you depending on your CONOPS. An ammunition ship carrying extra bombs for a CVN probably doesn't need a helo, it can get by with the CVN's helos coming to collect pallets of bombs to sling lift over. Otoh, a hospital ship might well benefit from having a helo hangar for maintaining medevac helos - hospitals have ambulances, afterall.


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