Navy Plans For 'Large Payload Subs' Based On New Columbia Class To Take On SSGN Role And More

The service is also eying a new sub-launched ballistic missile to replace Trident and could end up expanding its nuclear deterrent capabilities.

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The U.S. Navy has started exploring its options for a next-generation nuclear-armed submarine-launched ballistic missile to arm its future Columbia-class ballistic missile submarines and that design will incorporate elements of the existing Trident D-5. At the same time, the service will keep the Columbia production line "hot" to potentially build more of those boats or produce a conventionally-armed, multi-purpose "Large Payload Submarine." This latter design could end up packed with cruise missiles or hypersonic weapons, be able to act as an undersea mothership for special operations forces or large underwater drones, and more.

Various naval officers offered updates on the future of the Navy's strategic and other large submarine capabilities during talks at the Naval Submarine League’s annual symposium on Nov. 8, 2018. At present, the service expects to purchase at least 12 Columbias to replace its existing 14 Ohio-class ballistic missile submarines, or SSBNs. There are also plans to buy a minimum of five of the as yet unnamed Large Payload Submarine, also known as the Large-Volume Host Platform, primarily to replace the four additional Ohios that have been reconfigured as conventional cruise missile and special operations submarines, or SSGNs.

"What we are going to do is we’re going to keep the Columbia line hot," U.S. Navy Rear Adm. John Tammen, head of the Office of the Chief of Naval Operation's Undersea Warfare Division, said. "That gives us the option, if STRATCOM [U.S. Strategic Command] says we need more than 12, well then we can produce more than 12."

A wide array of different factors will influence that decision. Once the Ohio SSBNs leave service, the Columbias will form the full extent of the third leg of the United States' nuclear triad, a key component of America's nuclear deterrent. As such, it will be essential to ensure that there are enough of the new submarines to adequately meet those demands.

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An artists conception of the future USS Columbia.

General Dynamics Electric Boat, with assistance from Huntington Ingalls Industries’ Newport News Shipbuilding, is still finalizing the Columbia's design. Both companies will produce the submarines, with the construction scheduled to start on the lead ship in 2020. 

To try and help reduce costs, the Navy has already been ordering various components, including pre-fabricated Common Missile Compartment sections, each of which has four missile launch tubes. In August 2018, a quality control problem with the welds in some of those tubes emerged, which has now turned over to be extensive enough to require at least $27 million in repairs and a year of total time to fix. The Navy insists this will not impact the production schedule for the boats, which will cost approximately $7.2 billion each.

Any further issues with the design or future construction might alter the Navy's planned production totals. The figures are also based on an understanding of the deterrent requirements, which could always change in the coming years due to geopolitical concerns. That understanding could further evolve as the service starts to define what its next submarine-launched ballistic missile, which will replace the existing Trident D-5, will look like.

“If you look at the decisions that we made on Columbia, as we went down to 16 [launch] tubes [from 24 on the Ohios], part of that decision was made because there was an assumption that the reliability of this [follow-on] weapon system way out in the 2070s and 2080s will be just as reliable and supportable as it is today with the current Trident,” U.S. Navy Vice Admiral Johnny Wolfe, director of Strategic Systems Programs, explained at the Naval Submarine League event. What the Navy is presently calling Trident D-5 Life Extension 2, D5LE2, "won’t look like the D-5 that we’ve got today, it won’t be completely new, it will be somewhere in the middle," he added.

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The Ohio-class ballistic missile submarine USS Maryland fires a Trident D-5 submarine-launched ballistic missile during a test.

This new-ish missile is expected to stay in service through 2084, They will fully replace the existing D-5 Life Extension variant, or D5LE, which entered service in 2013, by around 2042. The Navy has yet to define what the improvements will be, but they will almost certainly include updated guidance and control systems with improved protection against electronic warfare and cyber attacks and espionage, additional countermeasures to defeat any enemy defenses, and reliability enhancements. They may also have new or modified nuclear warheads with scaleable, "dial-a-yield" effects.

All of this could impact the final number of Columbias the Navy decides to buy. The U.S. military's most recent Nuclear Posture Review calls for a minimum of 12 of the submarines, but does not state any firm maximum number. That same policy document outlined a controversial plan for both submarine-launched ballistic missiles and sea-launched cruise missiles armed with lower-yield warheads, which you can read about more here and here

President Donald Trump's administration has also been pushing for expanding the U.S. nuclear arsenal and has shown a disdain for international arms control agreements. At present, the United States is limited in how many SSBNs it can have at all by the terms of the New Strategic Arms Reduction Treaty (New START) with Russia. 

That agreement places hard limits on the total number various categories of deployed and non-deployed land-based intercontinental ballistic missile systems, submarine-launched ballistic missile systems, and nuclear-capable bombers. By only having 16 tubes per submarine on the Columbias, versus the 24 on the Ohios, the United States had already set the stage to free up room to potentially add in more SSBNs, or other systems the treaty covers, in the future. 

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The USS Ohio with her missile tubes open for inspection.

The arrangement will sunset no later than 2026, as well, which could render the entire issue moot if the United States and Russia can't agree on a new arms control deal. The Navy doesn't expect the future USS Columbia to head out on her first deterrent patrol until 2031.

If there still doesn't end up being a demand for more Columbias, the Navy already has a plan, though. "If STRATCOM doesn’t need more than 12, then we’re looking at what we call the Large-Volume Host Platform, where we’ll take that center section — we haven’t nailed down the concept — but there will be the ability to host vehicles on board inside that center section," Rear Admiral Tammen said.

The existence of this proposed submarine first public appeared in a report the Congressional Budget Office (CBO) released in October 2018 that reviewed Navy's latest shipbuilding plan for the 2019 through 2048 Fiscal Years. At present, the service already expects to buy one of these ships every three years after construction of the 12th Columbia class boat ends in 2036. 

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A chart showing the Navy's expected fleet sizes, including a portion representing its planned inventory of attack submarines, SSGNs, and Large Payload Submarines, between 2019 and 2048.

"The Navy provides little information about the size and capabilities of the large payload submarine," the CBO noted. "CBO assumed that it would be based on the Columbia class hull with its missile tube section reconfigured to perform whatever missions the Navy might want and that other sections of the ship would receive the necessary equipment and modifications to support the payloads the submarine might carry."

Those payloads remain almost entirely undefined, but would likely include some configuration of vertical launch system (VLS) arrays that could accommodate land-attack and anti-ship cruise missiles, including a top-secret supersonic submarine-launched anti-ship weapons now under development, and conventionally-armed hypersonic weapons. The ships would also be able to insert and extract special operations forces and deploy and recover unmanned undersea vehicles.

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A proposal from General Dynamics Electric Boat about how to turn a launch tube on the Ohio-class SSGNs into a hangar for unmanned undersea vehicles.

These are all existing and planned missions for the Ohio SSGNs and late-block Virginia-class attack submarines, the latter of which will feature a so-called Virginia Payload Module (VPM) with four, large multi-purpose launch tubes. The VLS capacity the converted Ohios already offer – each one can carry up to 154 Tomahawk land attack cruise missiles – means those four ships are in particularly high demand, which also puts serious strains on their crews. 

Unfortunately, the four Ohio SSGNs are also among the oldest boats in that class. The last one is supposed to head into retirement in 2026, after which the VPM-equipped Virginias are supposed to take over. Those smaller submarines won't be able to provide nearly the same amount of capability, though. Having a true replacement SSGN, and possibly more of them in total, would give Navy more conventional submarine firepower and other capabilities available in case a major conflict erupts.

The large size of a Columbia-based submarine could add additional flexibility, allowing it to act as a massive undersea mothership for the Navy's planned family of large, long-range unmanned undersea vehicles, which themselves will be able to perform a host of different missions. It may even allow for them to launch larger drone submarines in the future. 

The Navy has no capability like that at present, but only needs to look at Russia's investments in those kinds of special purpose submarines to see the potential benefits. The Russian Navy has a diverse fleet of mothership subs that can deploy deep-sea intelligence gathering platforms and launch nuclear-powered, nuclear-armed torpedoes and submersibles that may be able to strike at targets at extreme ranges.

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A graphic showing potential missions for large unmanned undersea vehicles from the US Navy's 2004 underwater drone roadmap.

Depending on the Large Payload Submarine's other performance characteristics, one or more of the boats might be able to take on more specialized missions, such as tapping undersea cables or sensitive salvage operations. The USS Jimmy Carter, last of the Seawolf-class attack submarines, gained a similar special mission mid-section and now focuses on intelligence gathering and underwater espionage missions.

The Navy is also hoping that the commonality in design with the Columbia will keep down the cost of the Large Payload Submarines. The service estimates that the unit price will be around $7 billion. CBO warns that the lack of clarity about the scope of the modifications to the existing design may lead to a greater cost per boat, closer to $7.6 billion, in the end.

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A graphic showing the USS Jimmy Carter's Multi-Mission Platform hull section. The Large Payload Submarine may have similar capabilities with its new multi-purpose section.

All of this comes amid a renaissance with regards to submarine and anti-submarine warfare capabilities within the Navy, driven primarily by concerns about advancing capabilities among potential "great power" competitors, such as Russia and China. In addition to its plans for its largest submarines, the service is also looking to develop a new class of larger attack submarines, as well as a host of other undersea capabilities.

However many Columbias and Large Payload Submarines the Navy ultimately buys, a mix of SSBNs with improved ballistic missiles and SSGN-like multi-mission boats looks set to offer the service important boosts in capability and capacity to conduct both strategic and conventional operations for decades to come.

Contact the author: jtrevithickpr@gmail.com