Ohio Replacement Submarine

The Ohio Replacement Submarine (formerly the SSBN-X Future Follow-on Submarine) is a future United States Navy submarine designed to replace the Trident missile-armed ballistic missile submarines.

Overview
The United States Department of Defense anticipates a continued need for a sea-based strategic nuclear force. The current Ohio class is expected to retire its first vessel by 2029, resulting in an expectation that a new platform must be seaworthy by that time. A replacement may cost over $4 billion per unit compared to Ohio's $2 billion ($2.9 billion in 2011 prices). More recent projections estimate the cost of each submarine at $6 to 8 billion. Twelve boats are planned as replacement for the Ohio class. Sources such as the Federation of American Scientists suggest that the number should be lower due to ever decreasing number of deterrent patrols in the Post Cold War era and as a cost reduction measure. However, Navy officials disagree stating that a dozen new SSBNs is the minimum number required despite issues in funding. Work on reducing the unit cost of boats 2-12 to $4.9 billion per boat (in base year 2010 dollars) is currently in progress. Several options were explored by the Navy including a variant of the nuclear attack submarines fitted with a missile housing, a dedicated SSBN, either with a new hull or based on an overhaul of the current Ohio.

With the cooperation of both Electric Boat and Newport News Shipbuilding, in 2007 the Navy began a cost control study. Then in December 2008, the Navy awarded Electric Boat a contract for the missile compartment design of the Ohio-class replacement, worth up to $592 million. Newport News is expected to receive close to 4% of that project. Though the Navy has yet to confirm an Ohio-class replacement program, then-United States Secretary of Defense Robert M. Gates, as of April 2009, confirmed that the Navy should begin such a program in 2010. The new vessel is scheduled to enter the design phase by 2014. It is anticipated that if a new hull design is used the program must be initiated by 2016 in order to meet the 2029 deadline. A report published in November 2011 stated that construction (of first-of-class) would start in 2019, the first boat would be launched in 2026 and commissioned in 2029. However, in 2012 Pentagon announced that the entire program is some two years behind schedule.

Early production boats will be armed with Trident II D5LE missiles (the LE suffix standing for life-extension). The Trident II D5LE will have a new guidance system and remain in service until 2042.

Representative Gene Taylor of Mississippi had threatened to block the project unless the Navy shares with the Congress an internal Analysis of Alternatives. However, Taylor was defeated by Steven Palazzo in the 2010 midterm election.

The high cost of the submarines is expected to cut deeply into Navy shipbuilding. The total lifecycle cost of the entire class is estimated at $347 billion.

The program entered the Technology Development Phase (known as Milestone A) in January 2011.

In December 2012, the Naval Sea Systems Command awarded Electric Boat a $2 billion contract covering design work on the boat itself, design work related to the Common Missile Compartments, and provides for "shipbuilder and vendor component and technology development, engineering integration, concept design studies, cost reduction initiatives using a design for affordability process, and full scale prototype manufacturing and assembly." Both the Navy and Electric Boat have acknowledged that affordability will be key in the development of the new vessel. Accordingly, the Navy has included bonuses in the cost-plus-fixed-fee contract to incentivize Electric Boat to keep costs down, despite the lack of competition in the program. Electric Boat has stated that it will use its Design for Affordability Program - originally developed to reduce costs on the Virginia class submarine - to reduce both construction and life-cycle costs. Detailed design work is expected to begin in 2017 with the first patrol scheduled for 2031. Under the current program, 12 new submarines will replace the 14 existing Trident-equipped Ohio class boats.

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


 * Expected 40-year service life
 * Life-of-the-ship nuclear fuel core that is sufficient to power the ship for its entire expected service life, unlike the Ohio-class submarines that 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 in and a length sufficient to accommodate a D-5 Trident II missile
 * Ship beam at least as great as the 42 ft beam of the Ohio-class submarines
 * 16 missile launch tubes instead of 24 missile launch tubes on Ohio-class submarines. A recent report (as of November 2012) suggested that the boats will have 12 SLBM silos/tubes. However, other sources do not support this.
 * 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

Also, the US Navy has 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 revealed, citing Naval Sea Systems Command, 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 boats 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 utilises an electric motor which turns the propeller of a ship/submarine. It is part of an wider (Integrated electric power) concept whose aim is to create an "all electric ship". Electric drive should reduce the life cycle cost of submarines while at the same time improving acoustic performance.

Turbo-electric drive had been used on US capital ships (battleships and aircraft carriers) in the first half of the twentieth century. Later on, two nuclear-powered submarines USS Tullibee (SSN-597) and USS Glenard P. Lipscomb (SSN-685) were equipped with turboelectric drive but experienced reliability issues during their service life and deemed underpowered and maintenance heavy. Currently, only the French Navy uses turboelectric drive on its nuclear-powered 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 which would utilise an advanced electric drive eliminating the need for both reduction gearing (mechanical drive) as well as steam turbines, however.

Various electric motors and generators are being or have been developed for both military and non-military vessels. Those being considered for application on future U.S. Navy submarines include: permanent magnet motors (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 US Navy appears to be focusing on permanent-magnet, radial-gap electric propulsion motors (e.g. Zumwalt-class destroyers use an advanced induction motor). Permanent magnet motors are being tested on the Large Scale Vehicle II for possible application on late production Virginia class SSNs as well as future submarines. On tests carried out by 2006, permanent-magnet motors achieved good overall results but failed to meet design requirements in acoustic performance. Permanent magnet motors (developed by Siemens AG) are used on Type 212 class submarines.

Reports on the Royal Navy Successor submarine (i.e., the class that will replace the Vanguard class SSBNs) state that the submarines 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 (i.e., generators powered by steam turbines) which would be connected to a non-penetrating electric junction at the aft end of the pressure hull, with a watertight electric motor mounted externally (perhaps in an Integrated Motor Propulsor arrangement), powering the pump-jet propulsor, although SSD concepts without pump-jet propulsors also exist.

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

In 2012, the US Navy's announced plans for its SSBN(X) to share a common missile compartment (CMC) design with the Royal Navy's proposed replacement for its own ballistic missile submarine. The CMC will house SLBMs in so-called quad packs.

Miscellaneous
In June 2012, the Arms Control Association warned that using highly enriched uranium fuel on nuclear submarines could become a nuclear proliferation issue. Modern US submarines use fuel enriched to over 90%, eliminating the need for reactor refueling during their service life. Fuel (uranium) enriched to over 90% is classified as weapons grade uranium and is used in nuclear warheads (weapons) production. The current nuclear Non-Proliferation Treaty does not prohibit the creation of weapons grade uranium if it is to be used for powering nuclear reactors on submarines. The association warns that certain countries may exploit this loophole so as to produce nuclear weapons, using a nuclear submarine construction program as a paravane. Finally, the association recommends that future submarines (e.g. Ohio class replacement) should return to reactors fueled by low enriched uranium.