SSBN-640 Benjamin Franklin-Class FBM Submarines

Generally similar to the SSBN-616 Lafayette-class, the twelve Benjamin Franklin (SSBN-640)-class submarines had a quieter machinery design, and were thus considered a separate class.

Lockheed commenced the TRIDENT I (C4) program in November of 1973 with the missile's IOC date established as 1979. The first of the new Ohio-Class submarines was authorized in 1974 but would not be available until 1979. Thus the Navy decided to borrow a page from the Extended Refit Program (ERP) book and a C3 to C4 SSBN "backfit" program was initiated in mid- 1976. The first boat in this SSBN backfit was the Francis Scott Key (SSBN-657). Following the deployment on 20 October 1979 of TRIDENT I (C4) missiles on the Francis Scott, other selected SSBNs were backfitted with the C4 [referred to as follow-on backfits]. Two additional SSBNs of this class (655 and 658) underwent the "pierside backfit" while three others (640, 641, and 643) were backfitted during their normally-scheduled second shipyard overhauls.

Two of these submarines [Kamehameha and James K Polk] were later converted to SEAL-mission capable attack submarines. In March of 1994 USS JAMES K. POLK (SSN 645) completed a 19-month conversion from ballistic missile submarine to attack/special warfare submarine at Newport News Shipbuilding. The January 1999 inactivation of the POLK leaves the KAMEHAMEHA (SSN 642) as the Navy's only former ballistic missile submarine equiped with Dry Deck Shelters (DDSs).