The U.S. Navy wants to expand the size of its planned fleet of Virginia-class submarines by 21 ships, service officials said.

The Navy's fleet of fast attack Virginia-class submarines, designed to replace the now-retiring Los Angeles class of submarines, is currently listed in the Pentagon's Acquisition Program Baseline, or APB, as a 30-ship program.

However, the Navy's Fiscal Year 2014 30-Year Shipbuilding Plan calls for continued construction of the Virginia-class attack submarines out to 2033, leading to a total fleet size of 51 ships, said Capt. David Goggins, the Navy's program manager for Virginia-class submarines.

"We are working with the Pentagon to update the APB to increase the size of the class from 30 to 51 or another number," Goggins said.

Merging the program's baseline numbers with what's specified in the Navy's shipbuilding plan is an effort that has been underway for months, Navy officials explained.

Cost overruns pushed back the Navy's goal of building two Virginia-class submarines per year by a decade.

Virginia-class submarines are fast-attack submarines armed with Tomahawk missiles, torpedoes and other weapons designed to allow the vessel to execute a range of missions. Goggins explained that the Virginia-class will provide a significant upgrade in littoral warfare compared to the Los Angeles-class.

For instance, the ships can be driven primarily through software code and electronics, thus freeing up time and energy for an operator who does not need to manually control each small maneuver.

"What enables this is the ship control system that we use. You can drive the ship electronically. This allows you the flexibility to be in littorals or periscope depth for extended periods of time and remain undetected," Goggins said.

The Virginia-class submarines are engineered with a "fly-by-wire" capability which allows the ship to quietly linger in shallow waters without having to surface or have each small move controlled by a human operator, Goggins said.

"There's a person at the helm giving the orders of depth and speed. There's always a person in the loop. The software is telling the planes and the rudder how to move in order to maintain a course and depth. You still have a person giving the electronic signal," he said.

Unlike their predecessor-subs, Virginia-class submarines are engineered with what's called a "lock out trunk" -- a compartment in the sub which allows special operations forces to submerge beneath the water and deploy without requiring the ship to surface, Goggins explained.

"SEALs and Special Operations Forces have the ability to go into a lock out trunk and flood, equalize and deploy while submerged, undetected. That capability is not on previous submarine classes," he added.

Unlike their "SSBN" Ohio-Class counterparts armed with nuclear weapons, the Virginia-Class "SSN" ships are purely for conventional attack, Navy officials said. However, one analyst theorized that perhaps, in the future, Virginia-class submarines could be configured to carry nuclear weapons.

"There is obviously a land-attack mission for the Virginia-class submarines because they launch Tomahawks. In the future, there could be a nuclear role for them because, once upon a time, Tomahawks were nuclear-capable. If you buy more Virginias, you get a flexible platform," said Christopher Preble, vice president for defense and foreign policy studies at the Cato Institute, a Washington, D.C.-based think tank.

With the nuclear-armed Ohio-class, its primary role is to quietly function as a vitally important deterrent, Preble added, explaining that it has been many years since nuclear weapons were carried on Navy surface ships.

The Virginia-class submarines are built by a cooperative arrangement between the Navy and Electric Boat, a subsidiary of General Dynamics and Newport News Shipbuilding, a division of Huntington Ingalls Industries.

Each industry partner constructs portions, or "modules," of the submarines which are then melded together to make a complete vessel, industry and Navy officials explained. Thus far, 10 Virginia-class subs have been delivered to the Navy, and seven are currently under construction. Like other programs, the Virginia-class submarines are broken up into procurement "blocks."

Blocks I and II, totaling 10 ships, have already been delivered.

At the same time, the program is getting ready for the formal arrival of its first Block III Virginia-class Submarine, the USS North Dakota, which is slated for delivery in January of next year.

On Dec. 22, 2008, the Navy awarded a contract for eight Virginia-class submarines. The third contract for the Virginia-class, or Block III, covering hulls numbered 784 through 791 -- is a $14 billion multi-year procurement, Navy officials said.

Multi-year deals are designed to decrease cost and production time by, in part, allowing industry to shore up supplies in advance and stabilize production activities over a number of years. Budget uncertainties connected to sequestration have made these deals more difficult.

The eighth Block III Virginia-class sub is slated to begin construction next month. The Block III subs, now under construction, are being built with new so-called Virginia Payload Tubes designed to lower costs and increase capability, Goggins explained.

Instead of building what most existing Virginia-class submarines have -- 12 individual 21-inch in diameter vertical launch tubes able to fire Tomahawk missiles -- the Block III submarines are being built with two-larger 87-inch in diameter tubes able to house six Tomahawk missiles each.

"For each one of these tubes, you have hydraulics and you have electronics. What we did for Block III is we went to two very large Virginia Payload Tubes -- now you have two tubes versus 12. It is much easier to build these two tubes," Goggins said.

Although the new tubes were conceived and designed as part of what the Navy calls its "Design for Affordability" strategy to lower costs, the move also brings strategic advantages to the platform, Goggins explained.

"In the future, beyond Tomahawk -- if you want to put some other weapon in here-- you can," Goggins said.

Also, for Block V construction, the Navy is planning to insert a new 97-foot-long section designed to house additional missile capability. In fact, the Navy's Capabilities Development Document, or CDD, for what's called the "Virginia Payload Modules" is finished up and now being assessed by Pentagon acquisition officials.

The Block V Virginia Payload Modules will add a new "module" or section of the submarine, increasing its Tomahawk missile firing capability from 12 to 40, Goggins added. The idea is to have additional Tomahawk or other missile capability increased by 2026, when the "SSGN" Ohio-Class Guided Missile Submarines start retiring in larger numbers, he explained.

Shipbuilders currently working on Block III boats at Newport News Shipyard, Va., say Block V will involve a substantial addition to the subs.

"Block V will take another cylindrical section and insert it in the middle of the submarine so it will actually lengthen the submarine a little and provide some additional payload capability," said Ken Mahler, Vice President of Navy Programs, Huntington Ingalls Industries.

The first Block V submarine is slated to begin construction in fiscal 2019, Navy officials said.

The President's 2014 budget request cites $5.4 billion for Virginia Class Submarines; the breakdown includes $3.7 billion to fund two ships in 2014 as part of a multi-year contract, plus $1.6 billion advance procurement dollars for two ships in 2015. The budget request also includes funding to prototype components and systems engineering for the Block V Virginia Payload Modules.

Overall, the Virginia-class submarine effort has made substantive progress in reducing construction time, lowering costs and delivering boats ahead of schedule, Goggins said.

"We're delivering submarines jointly with EB (Electric Boat) below budget up to 11 months ahead of the contract date. The Navy's 30-year shipbuilding plan calls for two per year. We will continue to look for ways to deliver early and under budget," Mahler said.

The last six Virginia-class submarines have been delivered ahead of schedule, Navy officials said. The six submarines were Block I and Block II Virginia-class submarines.

The program's current two-boats per year production schedule, for about $4 billion dollars, can be traced back to a 2005 challenge issued by then Chief of Naval Operations Adm. Mike Mullen. Mullen challenged the program to reduce production costs by 20 percent, saying that would allow the Navy to build two Virginia-class submarines per year, Goggins indicated.

This amounted to lowering the per-boat price of the submarines by as much as $400 million each, he added.

This was accomplished through a number of efforts, including an effort called "capital" investments wherein the Navy partnered with industry to invest in ship-building methods and technologies aimed at lowering production costs.

Other cost-reducing factors were multi-year contract awards, efforts to streamline production and work to reduce operations and sustainment, or O&S costs, Goggins explained.