The reasons are clear
For more than a decade, inadequate defense budgets and a high operational tempo have forced the U.S. military to shortchange modernization in order to preserve force structure and near-term readiness. Even when a service initiates a new major acquisition program such as the Air Force’s F-35 fighter, B-21 bomber and KC-46 tanker, the numbers that will be procured each year are relatively small. This means that the military will be required to operate older platforms for years and even decades longer than planned. These older systems require more maintenance and upgrades to critical systems, which drain the resources available for modernization.
Nowhere is the problem more challenging than in the Navy’s submarine force. The Navy operates two different fleets of submarines. One is the nuclear-powered ballistic missile submarines (SSBNs) that constitute a leg of the nuclear triad. There are 18 Ohio-class SSBNs, 14 of which carry Trident sea-launched ballistic missiles and four that were converted to employ sea-launched Tomahawk cruise missiles and are officially designated as guided-missile submarines, or SSGNs.
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The other underwater fleet consists of the nuclear-powered attack submarines (SSNs). The SSN fleet is comprised of three classes. The oldest are the 36 boats of the Los Angeles class. Next are the three Seawolf-class submarines. The newest of the SSNs and the only one currently in production is the Virginia class. 13 Virginia-class boats have been commissioned, and the Navy intends to continue producing them to replace the older classes of attack submarines.
There is an absolute requirement to modernize both the SSBN and SSN fleets. The Los Angeles-class boats are reaching the end of their nominal 33-year service life although life extension of 5 – 10 years is possible. The oldest of the Los Angeles-class SSNs, the USS Bremerton, was commissioned in 1981 and the youngest, the USS Cheyenne, was commissioned in 1996. So even with the most optimistic predictions about the Los Angeles class’ service life, the remaining 36 boats will have to be decommissioned over the next two decades.