Let's Have "Missile Barges" (and More) Now

A few years ago I noted that someone had proposed missile barges to accompany fleet ships Let's Talk Arsenal Ships and Missile Barges

Perhaps we should call it a self-propelled arsenal barge. SNAFU! has this image of a towed missile barge, the source of which is hard to track, but the caption on the picture indicates this is Russian design using a Sovremennyy-class destroyer as a towing ship*

There is this U.S. Navy image of what appears to be a JHSV pulling what appears to be a high speed missile barge:
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In the meantime, there is this 2005 article by Cmdr. John B. Perkins from the Armed Forces Journal, "Surface ship, submarine missions are coalescing" to ponder:

Andrew F. Krepinevich, director of the U.S. Center for Strategic and Budgetary Assessments (CSBA), alluded to this trend 10 years ago.

“Just as bombers are becoming relatively less important than the ordnance they carry,” he said, “so too might surface warships, which could evolve to become “barges” (with some perhaps operating below the surface) for advanced conventional munitions that can strike pre-designated targets at extended ranges.”

This concept makes the case that barges would be ideal as strike platforms of the future. The reference to the barges “operating below the surface” is the first precursor toward the idea of larger systems operating underwater.
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One of Krepinevich’s associates at CSBA put it this way: “This type of basic anti-navy architecture could be made more effective by incorporating increasingly sophisticated mines, active and passive sea-based sensor networks and quiet-attack submarines. Such architectures would have far lower barriers to entry (cost and learning) than carrier battle group operations, potentially enabling those competitors to leapfrog the carrier era and become major maritime competitors, at least in littoral waters. Absent a revolutionary breakthrough in ASW[anti-submarine warfare], naval power-projection operations could be driven sub surface.”
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This reference brings the point home in stark fashion: Technologies meant to find and destroy objects will become inexpensive and plentiful. The world’s strongest navy should not build anything but ships that employ the best covering tactics available. The CSBA suggested that the capital ship of the fleet in 2020 might be an arsenal ship — a missile-firing submersible armed with cruise and conventional ballistic missiles — and that such ships might be armed with a few hundred to a thousand missiles.

A distributed power projection navy might include several classes of arsenal ships and other submersible power projection forces in the fleet.

Recently, the DoD's Defense Advanced Research Projects Agency announced the concept of a "Sea Train":

The Sea Train vessels independently depart a port under their own power to reach a sortie point notionally 15 [nautical miles, or nmi] from the pier. The four independent vessels then begin the Sea Train mission by assembling in Sea Train configuration and completing a notional 6,500 nmi transit through varied sea state conditions that might require re-routing to optimize travel times or vessel seakeeping. The Sea Train then arrives at a disaggregation point, where the four vessels begin independent yet collaborative operations consisting of transits, loiters, and sprints in varied sea state conditions. The vessels then arrive at a sortie point to begin the aggregation process and conduct a Sea Train sprint from the operational area. The Sea Train then returns to normal transit speed for the remainder of the transit in varied sea state conditions, disaggregates outside of port and the vessels self-navigate to a pier.

There has been research in this area as set out here (pdf) in a paper by Igor Mizine and Gabor Karafiath:

A sea train is an arrangement of multiple hulls connected together to form a longer assembly of vessels. The sea train configuration takes advantage of fundamental hydrodynamic principles to reduce the drag of the assembled train below that of the individual components proceeding separately. In some circumstances the sea train arrangement can also offer operational advantages.

WHAT IF?

What if we develop large numbers of these "sea train" modules, including several loaded with generators, sensors, and "missiles in a box," they can serve as "accompanying assets" to a battle force. Such vessels, arriving in an area of interest could decouple, spread themselves out over a wide area and allow for a very wide distribution of lethality. 

Other "Sea Trains" may be equipped with machine shops, cranes, additive manufacturing equipment, or replenishment munitions or fuel. These units could be held in "safe havens" and brought to the fleet as needed. None of them need be manned which makes them far less expensive to construct. Each could carry sufficient habitability containers to provide comfort for technicians or oother personnel needed to operate equipment at their needed destination. 

 The larger the number of sea train modules, the great the the likelihood of needed components reaching the fleets on a timely basis. With enough units, even the expanse of the Pacific can be "shrunk."

As with WWII merchant shipping, some elements of a sea train could contain self-defense detection and weaponry, remotely monitored, but capable of self protection when authorized by a "human in the loop." Such equipment might include ASW-capable drones, or ASuW assets. 

Further, the use of unmanned but armed surface and subsurface could take the place of manned convoying ships.

COMMUNICATIONS

A key issue in discussing using unmanned vessels in the manner described above is communicating with those vessels to direct their positioning and, in the case of combat. controlling their weaponry. 

Obviously, with the towed missile barge such communications could be done through a cable connection piggy-backing on the tow line. 

With vessels within line of sight of the controller ship, the comms may be done through lasers or line of sight radios.  It is also conceivable that light weight fiber optic lines could connect units even several miles distant.

In certain environments, satellite links may be available. If those are blocked, manned or unmanned aircraft may serve as relay platforms. Indeed, the concept of solar powered high-altitude communications air systems placed to create an continuous link along the projected sea routes is not far-fetched. AeroVironment, among others, has been working along these lines for almost four decades. 

Explained in their video concerning their HAPS project - which could obviously be modified for military use, if needed:

The point is that we currently have the technology to distribute lethality at a much lower cost than the cost of new ships. We just need to get moving on experimenting with these technologies to find the right mix to provide the tools needed by our Navy and Marine Corps. 

*What SNAFU! wrote in 2012 to accompany those images was:

Worried about saturation attacks by anti-ship missiles?  Tow a couple of these behind a Burke loaded with about 1000 plus quad packed SM3's.  Want to savage a coast line?  Fill the other half with about 500 tomahawk land attack missiles.

UPDATE: DARPA "Sea Train" concept image:

DARPA offers up contract bid info here:

The Defense Advanced Research Projects Agency (DARPA) Tactical Technology Office (TTO) seeks to enable extended transoceanic transit and long range naval operations by exploiting the efficiencies of a system of connected vessels (Sea Train). The Sea Train will demonstrate long range deployment capabilities for a distributed fleet of tactical Unmanned Surface Vessels (USVs).