WASHINGTON -- The program to build a new class of nuclear-powered ballistic missile submarines for the US Navy passed a major procedural hurdle Jan. 4, the US Navy announced Monday, allowing engineers and designers to move to the detail design portion of the effort.

The Milestone B approval was granted by Pentagon acquisition chief Frank Kendall for the Columbia-class program, previously known as the Ohio Class Replacement (ORP) and as SSBN(X).

The US plans to design and build 12 Columbia-class submarines for a total acquisition cost of $100 billion – as measured in 2017 dollars – or $128 billion, as measured in total year dollars through the program, which stretches into the mid-2030s.

In a statement, Columbia program director Capt. David Goggins declared "the Navy is committed to delivering Columbia on time and within budget while taking advantage of every opportunity to achieve further cost savings."

The official tally for the acquisition cost has been baselined at $100 billion, pegged to the year of the Milestone B review.

With that approval, the Columbia class moves to the engineering and manufacturing development (EMD) phase of the program. The first ship is scheduled to be ordered in 2021.

"Milestone B enables the program to move into the Engineering and Manufacturing Development phase where we will focus our attention on achieving an 83 percent design maturity prior to construction start in 2021," Goggins said in the statement, adding that the next phase will be a production readiness review.  

General Dynamics Electric Boat is the Columbia program's prime contractor. The shipbuilder, with shipyards at Quonset Point, Rhode Island and Groton, Connecticut, is expected to grow its workforce from 14,000 to 18,000 employees to build the Columbias while continuing to build Virginia-class attack submarines.

Huntington Ingalls Industries Newport News Shipbuilding, GD's 50-50 partner in building the Virginia class, will built roughly a third of each Columbia.

The Columbia's name was officially announced Dec. 14 and will carry hull designation SSBN 826. Follow-on ships of the class will be designated SSBN 827 through 837.

US ballistic missile submarines carry the Trident D5 weapon with nuclear warheads. The Lockheed Martin-built missile will also arm Britain's new Successor-class submarines, now known as the Dreadnought-class after the name of the first ship.

The Navy expects the Columbia to carry out its first deterrent patrol during fiscal 2031.