Columbia Class Submarine

Columbia Class Submarine

The Columbia Class submarine, formerly known as the Ohio Replacement Submarine and SSBN-X Future Follow-on Submarine, is an upcoming class of nuclear submarines designed to replace the Ohio-class ballistic missile submarines in the United States Navy. The first submarine officially began construction on October 1, 2020, and is scheduled to enter service in 2031.


The Columbia class is being designed to replace the UGM-133 Trident II–armed Ohio-class ballistic missile submarines, whose remaining boats will be decommissioned, one per year, beginning in 2027. The Columbia class will take over the role of submarine presence in the United States’ strategic nuclear force.

Electric Boat is designing the Ohio replacement submarines with help from Newport News Shipbuilding. A total of 12 submarines are planned, with construction of the lead boat planned to begin in 2021. Each submarine will have 16 missile tubes, each carrying one Trident II D5LE missile. The submarines will be 560 feet (170.7 m) long and 43 feet (13.1 m) in diameter, as long as the Ohio-class design, and 1 foot (30 cm) larger in diameter.

In studies to determine how many submarines would be needed to support the United States’ strategic nuclear force, the U.S. Navy looked at the number of missiles required to be at sea and on station at any given time, the number of missiles each submarine should be armed with and the likelihood that a submarine will remain undiscovered by the enemy and be capable of launching its missiles. Also taken into consideration was how the maintenance schedule of each submarine will affect that boat’s availability to be deployed on mission. Cost-reduction studies explored design and construction possibilities, including adding missile tubes to the design of the Virginia-class attack submarine, building Ohio-class replacement submarines using updated Ohio-class designs, and developing an entirely new Ohio replacement submarine design.

Using the information from these studies, the Navy concluded that a new design would be the least expensive option that could meet all of the technical requirements. For example, both the modified Virginia-class and updated Ohio-class design options would have required an expensive mid-life refueling, whereas each Columbia-class nuclear core will last as long as the submarine is in service.

The design and technology development of the Columbia class is projected to cost $4.2 billion (fiscal 2010 dollars), although technology and components from the Ohio and Virginia classes are to be included where possible, to save money. The cost to build Columbia, the lead boat of the class, will be an estimated $6.2 billion (fiscal 2010 dollars). The Navy has a goal of reducing the average cost of the remaining 11 planned hulls in the class to $4.9 billion each (fiscal 2010 dollars). The total lifecycle cost of the entire class is estimated at $347 billion. The high cost of the submarines is expected to cut deeply into Navy shipbuilding.

In April 2014, the Navy completed a 300-page specification report for the Ohio Replacement Program submarines. There are 159 specifications including weapons systems, escape routes, fluid systems, hatches, doors, sea water systems, and a set length of 560 ft (170 m), partly to allow for sufficient volume inside the pressure hull.

In March 2016, the U.S. Navy announced that General Dynamics Electric Boat was chosen as the prime contractor and lead design yard. Electric Boat will carry out the majority of the work, on all 12 submarines, including final assembly. All 18 Ohio-class submarines were built at Electric Boat as well. Huntington Ingalls Industries’ Newport News Shipbuilding will serve as the main subcontractor, participating in the design and construction and performing 22 to 23 percent of the required work.

In late 2016, some 3,000 employees were involved, in Electric Boat alone, in the detailed design phase of the program, with the procurement of the first submarine scheduled for 2021. Completion of the first submarine is scheduled for 2030, followed by its entry into service in 2031. All 12 submarines are expected to be completed by 2042 and remain in service until 2085.

On 28 July 2016, it was reported that the first submarine of the class will be named Columbia, to commemorate the capital of the United States. The Columbia-class was officially designated on December 14, 2016, by Secretary of the Navy Ray Mabus, and the lead submarine will be USS Columbia (SSBN-826). The Navy wants to procure the first Columbia-class boat in FY2021.

On 28 October 2020, U.S. Navy Secretary Kenneth J. Braithwaite announced that the second submarine would be named USS Wisconsin.

General characteristics

Although still evolving, the following are some of the characteristics for the SSBN(X) design:

  • Expected 42-year service life (it is planned that each submarine will carry out 124 deterrent patrols during its service life)
  • Life-of-the-ship nuclear fuel core that is sufficient to power the submarine for its entire expected service life, unlike the Ohio-class submarines, which require a mid-life nuclear refueling
  • Missile launch tubes that are the same size as those of the Ohio class, with a diameter of 87 inches (2,200 mm) and a length sufficient to accommodate a D-5 Trident II missile
  • Beam at least as great as the 42-foot (13 m) beam of the Ohio-class submarines
  • 16 missile launch tubes instead of 24 missile launch tubes on Ohio-class submarines.
  • Although the SSBN(X) is to have fewer launch tubes than the Ohio-class submarine, SSBN(X) is expected to have a submerged displacement about the same as that of Ohio-class submarines

The U.S. Navy has also stated that “owing to the unique demands of strategic relevance, SSBN(X)s must be fitted with the most up-to-date capabilities and stealth to ensure they are survivable throughout their full 40-year life span.”

In November 2012, the U.S. Naval Institute, citing Naval Sea Systems Command, revealed additional design information:

  • X-shaped stern control surfaces (hydroplanes)
  • Sail-mounted dive planes
  • Electric drive
  • Off-the-shelf equipment developed for previous submarine designs (Virginia-class SSNs), including a pump-jet propulsor, anechoic coating and a Large Aperture Bow (LAB) sonar system.

The Columbia-class submarine may also be equipped with a Submarine Warfare Federated Tactical System (SWFTS), a cluster of systems that integrate sonar, optical imaging, weapons control etc.

Electric drive

Electric drive is a propulsion system that uses an electric motor that turns the propeller of a vessel. It is part of a wider (Integrated electric power) concept whose aim is to create an “all electric vessel”. Electric drive should reduce the life-cycle cost of submarines while at the same time reducing acoustic signature.

Turbo-electric drive had been used on U.S. capital ships (battleships and aircraft carriers) in the first half of the 20th century. Later on, two nuclear-powered submarines, USS Tullibee and USS Glenard P. Lipscomb, were equipped with turboelectric drives but experienced reliability issues during their service life and were underpowered and maintenance heavy. As of 2013, only the French Navy uses turboelectric drive on its nuclear-powered Triomphant-class submarines.

Conceptually, electric drive is only a segment of the propulsion system (it does not replace the nuclear reactor or the steam turbines). Instead, it replaces reduction gearing (mechanical drive) used on earlier nuclear-powered submarines. In 1998, the Defence Science Board envisaged a nuclear-powered submarine that would use direct energy conversion, eliminating the need for both reduction gearing as well as steam turbines.

In 2014, Northrop Grumman was chosen as the prime designer and manufacturer of the turbine generator units. The turbines convert thermal energy in the steam into mechanical energy, and the generators convert that mechanical energy into electrical energy. The electrical energy is then used for powering onboard systems as well as for propulsion via electric motor.

Various electric motors have and are being developed for both military and non-military vessels. Those being considered for application on future U.S. Navy submarines include permanent magnet motors (PMM) (being developed by General Dynamics and Newport News Shipbuilding) and a high-temperature superconducting (HTS) synchronous motors, being developed by American Superconductors as well as General Atomics.

More recent data shows that the U.S. Navy appears to be focusing on permanent-magnet, radial-gap electric propulsion motors (although the Zumwalt-class destroyer design switched from PMM to an advanced induction motor). Permanent magnet motors are being tested on the Large Scale Vehicle II for possible application on late production Virginia-class submarines, as well as future submarines. Permanent magnet motors, developed by Siemens AG, are used on Type 212 submarines, in service with the German and Italian navies.

Reports on the Royal Navy’s Dreadnought-class submarine, the class slated to replace the Vanguard class of ballistic missile submarines, state that the boats may have submarine shaftless drive (SSD) with an electric motor mounted outside the pressure hull. SSD was evaluated by the U.S. Navy as well, but it remains unknown whether the Ohio-class replacement will feature it. On contemporary nuclear submarines, steam turbines are linked to reduction gears and a shaft rotating the propeller/pump-jet propulsor. With SSD, steam would drive electric turbogenerators, powered by steam turbines, that would be connected to a non-penetrating electric junction at the aft end of the pressure hull, with a watertight electric motor mounted externally, possibly an Integrated Motor Propulsor arrangement, powering the pump-jet propulsor, although SSD concepts without pump-jet propulsors also exist. More recent data, including an Ohio Replacement scale model displayed at the Navy League’s 2015 Sea-Air-Space Exposition, indicates that the Ohio Replacement will feature a pump-jet propulsor visually similar to the one used on Virginia class. The class will share components from the Virginia class in order to reduce risk and cost of construction.

Common missile compartment

In December 2008, General Dynamics Electric Boat Corporation was selected to design the Common Missile Compartment that will be used on the Ohio-class successor.

In 2012, the U.S. Navy announced plans for its SSBN(X) to share a common missile compartment (CMC) design with the Royal Navy’s Dreadnought-class ballistic missile submarine. The CMC will house SLBMs in “quad packs”.


Type: Ballistic missile submarine (SSBN)
Displacement: 20,810 long tons (21,140 t) (submerged)
Length: 560 ft (171 m)
Beam: 43 ft (13 m)
Installed power: Nuclear reactor
Propulsion: Turbo-electric drive, pump-jet
Range: Unlimited
Complement: 155 (accommodation)
Sensors and
processing systems:
Enlarged version of the Virginia-class LAB sonar
Armament: 16 × Trident D5

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