The Navy will soon finish initially prototyping new weapons tubes for its Virginia-Class submarines designed to massively increase missile firepower, bring the platform well into future decades and increase the range of payloads launched or fired from the attack boats.

The new missile tubes, called the Virginia Payload Modules, will rev up the submarines’ Tomahawk missile firing ability from 12 to 40 by adding an additional 28 payload tubes – more than tripling the offensive strike capability of the platforms.

Prototyping of the new submarines amounts to early construction, meaning the missile tubes now being engineered and assembled with be those which will ultimately integrate into the completed boat. In essence, construction and metal bending for elements of what will become the first VPM are underway.

“Prototyping is underway,” Rear Adm. Charles Richard, Director of Undersea Warfare, told Scout Warrior in an interview.

Increasing undersea strike capability is a key element of the strategic calculus for the Navy as it continues to navigate its way into an increasingly high-tech and threatening global environment; potential adversaries are not only rapidly developing new quieting weapons and sonar detection technologies but also fielding long-range, precision-guided anti-ship missiles designed to target surface ship at long ranges.

The Chinese DF-21D and subsequent follow-on weapons in development are engineered to destroy carriers, destroyers and other surface vessels from distances as far as 900-miles off shore; if there is not a suitable defense for these kinds of long-range “anti-access/area-denial” weapons, the Navy’s ability to project power and launch attacks could be significantly limited. Carriers, for example, could be forced to operate further from the coastline at ranges which greatly complicate the aerial reach of many fighter aircraft which would launch from a carrier air-wing.

(This first appeared in Scout Warrior here.)

Navy strategy is therefore looking much more closely at the size and mission scope of its submarine fleet moving into the future, as undersea assets will most likely have an ability to conduct reconnaissance or strike missions far closer to an enemy shoreline – locations where it may be much harder for surface ships to operate given the fast-increasing threat environment. While the service is, of course, massively revving up its surface-ship offensive and defensive weaponry designed to allow vessels to better operate in so-called “contested” or high-threat areas, submarines are expected to increasingly play a vital role in a wide range of anticipated future mission requirements.

For example, improved increased sonar and quieting technologies referred to as Navy “acoustic superiority” are expected to allow submarines to conduct undersea reconnaissance missions much closer to enemy forces – and possibly behind defended areas. Such an ability could prove to be particularly relevant in coastal waters, shallow areas or islands such as portions of the South China Sea. These are precisely the kinds of areas where deeper draft surface ships may have trouble operating.

Building Virginia Payload Modules:

The Navy plans to engineer a new 84-foot long module into the length of the submarine in order to add four 87-inch launch tubes into the body of the ship.

The tooling and initial castings are now nearing completion in preparation for the first prototyping of the VPM tubes which will be finished in 2017, developers explained. Construction of the first VPM boat is slated for 2019 en route to being finished and operational by 2024 or early 2025. Initial work is underway at an Electric Boat facility in Quonset Point, R.I.

“The first tube fabrication begins next April,” Ken Blomstedt, Vice President of the Virginia-Class Program here at Electric Boat, told Scout Warrior in an interview.

The second submarine construction among the planned Block V Virginia-class attack submarine will be engineered with integrated VPM. It is called SSN 803, Blomstedt explained. The last 20 ships of the class, in Blocks V, VI and VII, will have VPM integrated.

A new massive module will be emerging from an Electric Boat manufacturing facility in Quonset Point, R.I.; the module will then be attached to a lower section of the missile tube.

“We are able to add that amount of strike capability in for a 15 percent increase in the price of the vessel - all on-track coming in very nicely. We are excited about the progress of the design. We are finishing up the castings of the integrated tube and hull,” Richard said.

“Tube and Hull” Forging:

Electric Boat developers tell Scout Warrior the VPM technical baseline has now been approved by the Navy, clearing the way for initial construction.

“The module consists of four 87-inch vertical payload tubes. The module is broken up into three sections – a forward support base, center section with four vertical payload tubes and an internal ballast tank to preserve or restore buoyancy for increasing the length of the ship,”

The technical baseline, which was informed by 39 key decisions, has been formally submitted and approved by the Navy as of February of this year.

“Will be exciting to see that first 184-foot module with VPM installed. Key to the module is using an integrated tube and hull approach,” Blomstedt added.

Electric Boat is using an emerging construction technique, called “tube and hull forging” design to expedite building and lower costs. The tactic involves connecting the top section of the tube to the pressure hull as one monolithic piece, he said.

“From a technology standpoint we are broadening the base with a one-piece casting. That piece comes into the missile tube fabricator,” Blomstedt said.

Along with firing Tomahawk missiles, the additional 87-inch payload tubes are being engineered to accommodate new weapons as they emerge and possibly launch other assets such as unmanned underwater vehicles.

The Navy will likely use the pace for a whole bunch of future payloads that they are just starting to think about,” Blomstedt said.

While it is certainly conceivable that Torpedoes and other weapons could eventually be fired from VPM tubes, Virginia-Class boats currently have a separate torpedo room with four torpedoes able to launch horizontally

A ballast tank has a pressure hull where the crew can operate, water levels inside the boat are adjusted to raise or lower the boat within the ocean; the weapons are designed to fire out of the launch tubes from a variety of different depths.

“When you submerge the ship, there is normally sea water all around the tubes

Navy Need for More Undersea Firepower;

The reason for the Virginia Payload Modules is clear; beginning in the 2020s, the Navy will start retiring four large Ohio-class guided-missile submarines able to fire up to 154 Tomahawk missiles each. This will result in the Navy losing a massive amount of undersea fire power capability, Navy developers have explained.

From 2002 to 2008 the U.S. Navy modified four of its oldest nuclear-armed Ohio-class submarines by turning them into ships armed with only conventional missiles -- the USS Ohio, USS Michigan, USS Florida and USS Georgia. They are called SSGNs, with the “G” designation for “guided missile.” These boats were among US military assets that provided firepower during action against Libya in 2011 – by firing Tomahawks from undersea at key locations such as enemy air defenses designed to clear the way for strike aircraft.

If the VPM action is not taken, the Navy will lose about 60-percent of its undersea strike launchers when the SSGNs retire in the 2020s. When VPM construction begins in 2019, that 60-percent shortfall will become a 40-percent shortfall in the 2028 timeframe.

Accordingly, building VPMs is designed to eliminate the loss of firepower. The rationale for accelerating VPM is to potentially mitigate that 40-percent to a lower number, Navy developers have said.

Virginia-class submarines, engineered to replace the 1980s-era Los Angeles-class attack submarines, are being built in block increments. Blocks I and II, totaling 10 ships, have already been delivered to the Navy. Block III boats are currently under construction. In fact the first Block III boat, the USS North Dakota, was delivered ahead of schedule in August of 2014.

The first several Block IV Virginia-class submarines are under construction as well -- the USS Vermont and the USS Oregon. Last April, the Navy awarded General Dynamics’ Electric Boat and Huntington Ingalls Industries Newport News Shipbuilding a $17.6 billion deal to build 10 Block IV subs with the final boat procured in 2023.

Also, design changes to the ship, including a change in the materials used for the submarines’ propulsor, will enable Block IV boats to serve for as long as 96-months between depots visits or scheduled maintenance availabilities, Navy developers explained.

Kris Osborn became the Managing Editor of Scout Warrior in August of 2015. His role with Scout.com includes managing content on the Scout Warrior site and generating independently sourced original material. Scout Warrior is aimed at providing engaging, substantial military-specific content covering a range of key areas such as weapons, emerging or next-generation technologies and issues of relevance to the military. Just prior to coming to Scout Warrior, Osborn served as an Associate Editor at the Military.com. This story originally appeared in Scout Warrior.