The Electric Boat unit of General Dynamics this week started building the yet-unnamed SSS-787 Virginia-class attack submarine — the 13th vessel of the class and the second to begin construction this year.

This is the first time in 22 years the Navy is building two same-class subs in the same year, the service notes. The Navy pursued the two-per-year sub-building contracts to help curb costs and cut construction times. Electric Boat won the $1.2 billion construction contract in April.

“To get to this important point, our Navy/industry shipbuilding team executed a very successful design-for-affordability program that yielded significant cost savings and has allowed the Navy to increase production in a fiscally responsible manner,” says Rear Adm. David Johnson, program executive officer for submarines. “A great deal of our success comes from increasing construction efficiencies.”

The last two subs, he says, were delivered in 65 months, eight months before their contracted delivery date. “We are well on our way to getting that number down to 60 months for our two fiscal year 2012 authorized boats [SSN-788 and SSN 789],” he said in a statement.

The design-for-affordability program involved redesigning portions of the Virginia class to reduce costs and construction time, the Navy notes. “The program has yielded significant cost savings for the Virginia class, reducing its per-submarine acquisition costs by nearly 20 percent while shortening their construction span from 84 months to 60,” the service says. “These efforts significantly contributed to the Navy’s transition to building two Virginia class submarines per year.”

“Our team has been diligently driving down the cost and construction time of these submarines to get to this key two per year milestone,” says Capt. Michael Jabaley, who was recently selected to be a rear admiral and Virginia-class program manager. “Building two submarines per year is the most economical way to procure these boats.”

Navy officials cite the Virginia-class program as a template to procure and build other vessels such as the proposed SSBN(X) replacement for ballistic missile submarines. Some analysts have suggested the Navy should delay the SSBN(X) and use modified Virginias for ballistic missile missions to save on costs.

The redesigned Virginia would cost about $3.5 billion, according to naval analyst and author Norman Polmar, compared to the SSBN(X) vessel slated to cost between $5 billion and $7 billion per each — provided the design and building of the new class plays out as planned.

The Navy has never been shy about investing in its submarines, which ranked as the third-highest service expense between 1999 and 2008, with about $16.2 billion in contracts and contract modifications, according to an exclusive Aviation Week Intelligence Network analysis of Pentagon contracting data aggregated by the National Institute for Computer-Assisted Reporting. That amount does not include what the Navy spends on the nuclear reactors to run the subs, as well as nuclear-powered aircraft carriers.