Benjamin Franklin-Class (SSBN-640) Ballistic Missile Submarines

Benjamin Franklin-Class (SSBN-640) Ballistic Missile Submarines

The Benjamin Franklin class consisted of 12 nuclear-powered ballistic missile submarines. These subs, completed between 1963-67, stood out for being the quietest and heaviest among all Lafayette types.

Despite their visual resemblance to the Lafayette class, the Benjamin Franklin class boats distinguished themselves with improved and quieter machinery. They also accommodated 28 additional crew members.

Benjamin Franklin Class
Length:425 ft (129.57 m)
Height:32 ft (9.75 m)
Width:33 ft (10.06 m)
Weight:7,350 tons surfaced
8,250 tons submerged
Armament:16 steam ejection tubes for Polaris, Poseidon & Trident missiles and four 21-inch torpedo tubes
Speed:21 knots on the surface
16 knots submerged
Powerplant:Single S5W pressurized water nuclear reactor
Crew complement:141 men; 15 officers, 126 enlisted
Contractors:General Dynamics Electric Boat Division, Mare I NSYd, Newport News, Portsmouth NSYd
Names of submarines:(640) Benjamin Franklin,
(641) Simon Bolivar,
(642) Kamehameha,
(643) George Bancroft,
(644) Lewis and Clark,
(645) James K. Polk,
(654) George C. Marshall,
(655) Henry L. Stimson,
(656) George Washington Carver,
(657) Francis Scott Key,
(658) Mariano G. Vallejo,
(659) Will Rogers

This class formed the last submarines of the “41 for Freedom” submarines that served as the cornerstone of the US underwater deterrent strategy during most of the Cold War.

The Ohio Class replaced the Benjamin Franklin- and Lafayette-class ballistic missile submarines in the 1980s.



The Benjamin Franklin class submarines, known as SSBN 640, were redesigned versions of the Lafayette class, based on the BUSHIPS sub-design 216. The fleet consisted of two distinct designs. The first six submarines, including Benjamin Franklin, Simon Bolivar, Kamehameha, George Bancroft, Lewis and Clark, and James K. Polk, were based on the SCB 216 Mod 2 design.

Port bow view of USS Mariano G. Vallejo underway in San Francisco Bay.
Port bow view of USS Mariano G. Vallejo underway in San Francisco Bay. (National Archives)

The other six, including George C. Marshall, Henry L. Stimson, George Washington Carver, Francis Scott Key, Mariano G. Vallejo, and Will Rogers, followed the SCB 216 Mod 3 design.

The SCB 216 Mod 2 design incorporated quiet machinery by mounting the turbines and propeller shaft housing on shock-absorbing material, reducing noise. Additional noise reduction measures included the installation of cork and rubber panels in high-noise areas. The speed performance matched that of the 627 class, capable of over 20 knots when submerged.

An HH-46A Sea Knight helicopter hovers over the USS George Washington Carver (SSBN-656) while in the Mediterranean Sea on August 1, 1977. (National Archives)

Despite appearing large externally, the Lafayette, James Madison, and Benjamin Franklin class submarines were compact inside. Spaces were efficiently used with triple bunking being standard. The largest open area was the enlisted mess area, and the medical facility was equivalent to four phone booths, with the officers’ wardroom serving as an operating theater in emergencies.

The 640 class had the same SCB 216 hull design as the previous 616 and 627 class submarines, with a length of 425 feet and a beam of 33 feet. They were equipped with an updated BQR-21 conformal sonar featuring Digital Multi-beam Steering (DIMUS). Some submarines in the 640 class were later modified with twin vertical end plate stabilizers, replacing the single tall fin/rudder.

Starboard view of USS Lewis and Clark (SSBN-644) somewhere in the Pacific Ocean on febrero 1, 1991
Starboard view of USS Lewis and Clark (SSBN-644) somewhere in the Pacific Ocean on February 1, 1991. (National Archives)

The Benjamin Franklin Class, along with the Lafayette and James Madison Class submarines, used either the Towed sonar array BQR-15 or BQR-17, depending on when it was installed. The BQR-15 was the earlier version, while the BQR-17 was a later upgrade. This sonar system was set on a long wire from the right side of the submarine. It carried devices that could listen to enemy submarines or ships.

The class of submarines also had different types of distractions, like the WLR-8. This tool mimicked the noises that other submarines make. The 640 Class submarines were also equipped with devices that explode and make noise, which are launched from the middle of the submarine. This noise hides the submarine’s noise and allows it to get away from enemies who might have noticed it.


The Benjamin Franklin class submarines were initially launched and commissioned with the Polaris A-3 ballistic missile.

However, between November 1972 and September 1974, during their first overhaul periods, they were upgraded to the Poseidon C-3 missile.

Trident C4 missile fired from USS Henry L. Stimson (SSBN-655) on December 15, 1984.
Trident C4 missile fired from USS Henry L. Stimson (SSBN-655) on December 15, 1984. (National Archives)

Further enhancements were made as the more powerful, longer-range Trident I C-4 became available, and these were also integrated into the subs.

Notably, the USS Benjamin Franklin, Simon Bolivar, and George Bancroft received their upgrades during their second overhaul. In contrast, Henry L. Stimson, Francis Scott Key, and Mariano G. Vallejo received their back fits pier side by a subtender.

Incorporating the Trident necessitated an electronic upgrade, including improved navigational and satellite receiving systems.


Every submarine in the class used a 15,000 shaft horsepower Westinghouse S5W nuclear reactor, which was cooled by high-pressure water, for power.


Like other submarines in the 616 and 627 classes, the Benjamin Franklin (640) class was equipped with four Mark 65 torpedo tubes at the front, each 21 inches in size.

These tubes held Mark 48 torpedoes that served two purposes and were managed by a Mark 113 Mod 9 system for firing the torpedoes.


The 12 ships of the class were commissioned between 1965 and 1967. In the fiscal 1965 shipbuilding program, plans proposed four additional units of this class to complete the envisioned 45-submarine Polaris force. However, these ships were never constructed.

USS Kamehameha (SSBN-642) commissioning ceremony on diciembre 10, 1965
USS Kamehameha (SSBN-642) commissioning ceremony on diciembre 10, 1965. (National Archives)

The average price for a 640-class submarine stood at roughly $66 million per boat. The addition of the nuclear reactor, electronics, weapon systems, and specialized equipment raised the total to $116 million. This figure excludes the price of 16 missiles, which cost an average of $1.7 million each, excluding the warheads.

No.NameBuilderKeel LaidLaunchedComm.
SSBN 640Benjamin FranklinElectric Boat25 May 19635 Dec 196422 Oct 1965
SSBN 641Simon BolivarNewport News17 Apr 196322 Aug 196429 Oct 1965
SSBN 642KamehamehaMare I NSYd2 May 196316 Jan 196510 Dec 1965
SSBN 643George BancroftElectric Boat24 Aug 196320 Mar 196522 Jan 1966
SSBN 644Lewis and ClarkNewport News29 Jul 196321 Nov 196422 Dec 1965
SSBN 645James K. PolkElectric Boat23 Nov 196322 May 196516 Apr 1966
SSBN 654George C. MarshallNewport News2 Mar 196421 May 196529 Apr 1966
SSBN 655Henry L. StimsonElectric Boat4 Apr 196413 Nov 196520 Aug 1966
SSBN 656George Washington CarverNewport News24 Aug 196414 Aug 196515 Jun 1966
SSBN 657Francis Scott KeyElectric Boat5 Dec 196423 Apr 19663 Dec 1966
SSBN 658Mariano G. VallejoMare I NSYd7 Jul 196423 Oct 196516 Dec 1966
SSBN 659Will RogersElectric Boat20 Mar 196521 Jul 19661 Apr 1967


The Simon Bolivar, the first Benjamin Franklin class submarine, was launched on August 22, 1964, a year later than expected, and was commissioned on October 29, 1965, a week following the Benjamin Franklin. It embarked on its first deterrent patrol in the Atlantic on April 27, 1966, while Benjamin Franklin joined the Pacific fleet on May 7.

The class deployment was concluded on October 3, 1967, as the USS Will Rogers embarked on its first war patrol.

USS Mariano G. Vallejo (SSBN-658) returning to Kings Bay after completing the Navy's 2,500th deterrent patrol
USS Mariano G. Vallejo (SSBN-658) returning to Kings Bay after completing the Navy’s 2,500th deterrent patrol (National Archives)

Initially, the submarines in this class were deployed with the Polaris A-3 missile. However, beginning in November 1972, they started being equipped with Poseidon C-4, with the rearming process concluding by September 1974.

In the following table, the details of the conversion to Poseidon are shown:

No.FY ProgramConversion YardStartComplete
SSBN 6401971Electric Boat25 Feb 197115 May 1972
SSBN 6411971Newport News15 Feb 197112 May 1972
SSBN 6421972Electric Boat15 July 197127 Oct 1972
SSBN 6431971Portsmouth NSYd28 Apr 197131 July 1972
SSBN 6441971Puget Sound NSYd30 Apr 197121 July 1972
SSBN 6451972Newport News15 July 197117 Nov 1972
SSBN 6541972Puget Sound NSYd14 Sep 19718 Feb 1973
SSBN 6551972Newport News15 Nov 197122 Mar 1973
SSBN 6561972Electric Boat12 Nov 19717 Apr 1973
SSBN 6571972Puget Sound NSYd20 Feb 197217 May 1973
SSBN 6581973Newport News21 Aug 197219 Dec 1973
SSBN 6591973Portsmouth NSYd16 Oct 19728 Feb 1974

On October 20, 1979, the submarine USS Francis Scott Key became operational with the Trident I missile.

The Trident I deployment was finalized on July 20, 1982, following the rearming of Francis Scott Key, Henry L. Stimson, Mariano G. Vallejo, Benjamin Franklin, Simon Bolivar, and George Bancroft.


The Benjamin Franklin class was decommissioned in response to the START I nuclear reduction initiatives, and all missile systems were removed. These initiatives required a significant reduction in strategic weapon systems, including existing and future intercontinental missile systems.

By 1992, the Lewis and Clark, George Marshall, George W. Carver, and Will Rogers had been decommissioned.

Crewmen aboard USS Francis Scott Key (SSBN 657) welcome the USS Tennessee (SSBN 734) of the Ohio Class as this last one arrives at Naval Submarine Base Kings Bayfor the first time.
Crewmen aboard USS Francis Scott Key (SSBN 657) welcome the USS Tennessee (SSBN 734) of the Ohio Class as this last one arrives at Naval Submarine Base Kings Bay for the first time. The Ohio class submarines replaced all previous SSBN submarines. (National Archives)

By the end of 1993, Benjamin Franklin, Simon Bolivar, George Bancroft, and Henry L. Stimson were put on stand-down status, leaving only Kamehameha, James K. Polk, and Mariano G. Vallejo in service.

This resulted in only five operational Lafayette-style ballistic missile submarines by 1994.

No.NameDecomm.StrikenBroken up
SSBN 640Benjamin Franklin23 Nov 199323 Nov 19931995
SSBN 641Simon Bolivar8 Feb 19958 Feb 19951995
SSBN 642Kamehameha4 Aug 20012 Apr 20022003
SSBN 643George Bancroft21 Sep 199321 Sep 19931998
SSBN 644Lewis and Clark1 Aug 19921 Aug 19921996
SSBN 645James K. Polk8 Jul 19998 Jul 19992000
SSBN 654George C. Marshall24 Sep 199224 Sep 19921994
SSBN 655Henry L. Stimson5 May 19935 May 19931994
SSBN 656George Washington Carver18 Mar 199318 Mar 19931994
SSBN 657Francis Scott Key2 Sep 19932 Sep 19931995
SSBN 658Mariano G. Vallejo10 Mar 199510 Mar 19951995
SSBN 659Will Rogers12 Apr 199312 Apr 19931994

Two of these submarines, the Kamehameha and the James K. Polk, were converted into attack submarines suitable for SEAL missions in March 1994.

When the Polk was inactivated in January 1999, the Kamehameha remained the only former ballistic missile submarine with dry deck shelters. However, by 2002, the Kamehameha was also decommissioned.

Further reading


  • Polmar, N., Moore, K. J. (2014). Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines. United States: Potomac Books, Incorporated.
  • Polmar, N. (1993). The Naval Institute Guide to the Ships and Aircraft of the U.S. Fleet, 15th Edition. United States: Naval Institute Press.
  • Gibson, J. N. (1996). Nuclear Weapons of the United States: An Illustrated History. United States: Schiffer Publishing.
  • Adcock, A. (1993). U.S. Ballistic Missile Subs in Action. United States: Squadron/Signal Publications.
  • Friedman, N. (1995). U.S. submarines through 1945: an illustrated design history. United States: Naval Institute Press.


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Javier Guerrero
Javier Guerrero
Javier is the editor @ Nuclear Companion and loves to investigate and write about the cold war.

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