Ethan Allen-Class (SSBN-608) Ballistic Missile Submarines

Ethan Allen-Class (SSBN-608) Ballistic Missile Submarines

The Ethan Allen Class of fleet ballistic missile submarines were larger and more advanced engineered than their predecessors, the George Washington Class.

Unlike the George Washington Class, whose hulls were retrofitted to house missiles, the Ethan Allen Class was uniquely crafted from the keel up with the specific intent of launching ballistic missiles. Their design marked a significant improvement in size, structure, and missile accommodation, solidifying their role as dedicated Fleet Ballistic Missile Submarines (FBMs).

Ethan Allen class
Length:410 ft 5 in (125.13 m)
Height:32 ft (9.75 m)
Width:33 ft (10.06 m)
Weight:6,900 tons surfaced
7,900 tons submerged
Armament:16 air ejection tubes for Polaris 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:136 men; 12 officers, 124 enlisted
Contractors:General Dynamics Electric Boat Division, Newport News
Names of submarines:(608) Ethan Allen,
(609) Sam Houston,
(610)Thomas A. Edison,
(611) John Marshall,
(618) Thomas Jefferson

Although they were not as sophisticated as the subsequent Lafayette Class, the Ethan Allen Class subs were the first of their kind to achieve a deep-diving capacity in the U.S. FBM fleet.



The Ethan Allen Class of nuclear ballistic missile submarines was the first fleet intentionally designed to launch ballistic missiles.

The submarines, based on the SCB-180 submarine design, implemented design elements from the Thresher (SSN 593) class, such as the deep-diving hull made of Hy 80 steel, enabling them to exceed the George Washington Class in diving depth.

An aerial bow view of the nuclear-powered strategic missile submarine USS Thomas Jefferson (SSBN-618) underway. (National Archives)

With a submerged weight of 7,900 tons, the Ethan Allen Class submarines were notably larger than the George Washington Class, which weighed 6,700 tons. The hull of these submarines measured 410 feet in length and thirty-three feet in width, featuring a surface displacement of 6,900 tons.

They possessed four torpedo tubes compared to the six of the George Washington Class, and incorporated Thresher-type machinery quieting features, along with improved accommodations.

USS Ethan Allen (SSBN-608) underway in Atlantic during December 1967
Broadside view of the USS Ethan Allen (SSBN-608) underway in the Atlantic during December 1967 (U.S. Navy)

The Thresher significantly influenced the Ethan Allen Class’s interior design, systems, and depth capabilities, echoing how the Skipjack had guided the George Washington Class’s design.


The Ethan Allen Class of submarines was initially armed with sixteen Polaris A-2 (UGM-27B) Submarine-Launched Ballistic Missiles (SLBMs), having a reach of 1,500 nautical miles, marking a 300-mile increase from the Polaris A-1. The A-2 missile carried the same W47 warhead as the A-1, but it featured an enhanced yield of 1.2 megatons.

Polaris A2 missile on the launch pad at Cape Canaveral
Polaris A2 missile on the launch pad at Cape Canaveral. (U.S. Navy photo)

The submarines used the MK 80 missile fire control system, the same as the George Washington Class, to launch the missiles.

The Ethan Allen submarine was the first to launch the A-2 missile on October 23, 1961, and it began its initial patrol with the A-2 missile on June 26, 1962.

A notable historical event occurred on May 6, 1962, when Ethan Allen fired a Polaris A-2 missile in the Christmas Island Pacific Test Area, marking the first comprehensive U.S. test of a ballistic missile that included nuclear warhead detonation.

USS Sam Houston (SSBN 609) loads a Polaris A-2 missile in 1965. (National Archives via Al Adcock)

Between 1965 and 1966, the Ethan Allen Class submarines were retrofitted with the more advanced Polaris A-3 (UGM-27C) missile and a gas generator/steam ejection missile launch system, improving the range to 2,500 statute miles. The refitting also included an upgrade to the Mk 84 fire control system, which worked with the A-3 missile and gas-steam missile ejectors.


The water-cooled Westinghouse 5SW reactor powered the Ethan Allen Class submarines.

The submarines USS Ethan Allen (SSBN 608), USS Sam Houston (SSBN 609), and USS Thomas A. Edison (SSBN 610) were equipped with turbines designed by Westinghouse, whereas the USS John Marshall (SSBN 611) and USS Thomas Jefferson (SSBN 618) were installed with turbines from General Electric.

USS John Marshall (SSBN-611) (National Archives)

All these ballistic missile submarines utilized a seven-blade propeller. The 15,000 horsepower reactor allowed these submarines to reach a maximum speed of over twenty-one knots when submerged.


The Ethan Allen Class was equipped with four 21-inch torpedo tubes positioned in the bow, solely for defensive purposes.

They initially held either the Mk 16 Mod 6 or the Mk 37 electric torpedo. However, in 1974, the multi-purpose Mk 48 torpedo became accessible and took over as the standard torpedo for all Fleet Ballistic Missile (FBM) submarines.

The Mark 112 Mod 2 system, which was connected directly to the onboard sonar, and the Mark 2 Mod 3 Ships Inertial Navigation System (SINS), served as the torpedo’s fire control.


The Polaris program, initiated in December 1957, initially planned to build five unique submarines to carry and launch a missile with a range of 1,800 miles. However, the acceleration of the program in December 1957 led to the quick creation of the five George Washington class submarines instead.

On August 22, 1958, President Eisenhower initially held back the funding for the first four Ethan Allen submarines, but reversed his decision by the end of the year, authorizing the construction of the USS Ethan Allen. Its construction commenced immediately, and it was launched at the General Electric Boat yards in Groton, Connecticut, on November 22, 1960.

No.NameBuilderKeel LaidLaunchedComm.
SSBN 608Ethan AllenElectric Boat14 Sep 195922 Nov 19608 Aug 1961
SSBN 609Sam HoustonNewport News28 Dec 19592 Feb 19616 Mar 1962
SSBN 610Thomas A. EdisonElectric Boat15 Mar 196015 Jun 196110 Mar 1962
SSBN 611John MarshallNewport News4 Apr 196015 Jul 196121 May 1962
SSBN 618Thomas JeffersonNewport News3 Feb 196124 Feb 19624 Jan 1963

The construction of the Ethan Allen class was divided into two locations. The first and third submarines, USS Ethan Allen (SSBN 608) and USS Thomas A. Edison (SSBN 610) were constructed at Electric Boat on the Thames River in Groton, Connecticut.

The second, fourth, and fifth submarines, USS Sam Houston (SSBN 609), USS John Marshall (SSBN 611), and USS Thomas Jefferson (SSBN 618), were built by Newport News Shipbuilding on the James River, Virginia.

The submarines were launched and commissioned between 1961 and early 1962. They made their initial deterrent patrols from late 1962 to early 1963, departing from Charleston, South Carolina, where they also received their basic missile loadouts.


After the completion of sea trials, Ethan Allen launched its inaugural 1,800-mile range Polaris A-2 missile on October 23, 1961. It was the first successful submerged launch of this second-generation Polaris missile.

The USS Ethan Allen (SSBN 608) launched a Polaris A-2 missile off the coast of Florida near Cape Canaveral on October 23, 1961. This event marked the first underwater launch of the second-generation Polaris missile.
The USS Ethan Allen (SSBN 608) launched a Polaris A-2 missile off the coast of Florida near Cape Canaveral on October 23, 1961. This event marked the first underwater launch of the second-generation Polaris missile. (U.S. Navy photo)

By May 1962, it joined Joint Task Force 8 at the Pacific nuclear testing range. Here, on May 6, 1962, at exactly 14:17:49 PDT, Ethan Allen made history by launching a Polaris A-1 missile equipped with a nuclear warhead.

This test, known as Shot Frigate Bird of test series Dominic 1, was the first-ever U.S. launch of a Polaris missile with a nuclear warhead. The test, conducted near Christmas Island, was the only full-systems U.S. strategic missile test that included a launch through detonation (Operation Frigate Bird).

The first-ever U.S. launch of a Polaris missile with a nuclear warhead: Shot Frigate Bird of test series Dominic 1
The first-ever U.S. launch of a Polaris missile with a nuclear warhead (U.S. Navy)

The first launch of a Submarine-Launched Ballistic Missile (SLBM) fitted with a thermonuclear warhead took place on October 20, 1961. This was executed by a Soviet Project 629 submarine that launched an R-13 missile. This missile was equipped with a one-megaton warhead, which detonated at the Novaya Zemlya test range in the Arctic during a test named “Rainbow.”

After this test, Ethan Allen returned to the East Coast, was rearmed with the Polaris A-2, and initiated its first operational patrol on June 26, 1962. This successful deployment set the stage for the future service of four Ethan Allen class submarines in the North Atlantic within the following six months. By April 14, 1963, the USS Sam Houston reached Izmir, Turkey, marking the arrival of the first FBM submarine of this class in the Mediterranean.

These submarines were progressively deployed throughout their service life across various regions, eventually replacing the Jupiter IRBMs based in Turkey. They went on to operate in the Atlantic and Mediterranean out of Holy Loch, Scotland, until the mid-1970s.

John F. Kennedy on board the USS Thomas Edison (SSBN-610) on April 14, 1962, during the president's visit to the U.S. Atlantic Fleet.
John F. Kennedy on board the USS Thomas Edison (SSBN-610) on April 14, 1962, during the president’s visit to the U.S. Atlantic Fleet.(U.S. Navy photo)

Post the deployment of the Poseidon missile, they were relocated to the Pacific to join the George Washington class at the Guam submarine base. This transition was complete by August 10, 1973, marking the shift from Atlantic to Pacific operations.

In line with the upgrade in their operations, all Ethan Allen class submarines were equipped with the advanced Polaris A-3T missile by the time of their Pacific redeployment. Specifically, Ethan Allen was re-armed with this missile in October 1972, and its first patrol with the Polaris A-3T began on August 29, 1974.

The last Polaris A-2 was retired from service with the return of the USS John C. Marshall on June 9, 1974.

Conversion to attack submarines

In the Pacific, the Ethan Allen class submarines were conducting deterrent patrols until 1981. However, they were nearing the limits of their structural and nuclear reactor lifespans by 1980. To address this, and to comply with the SALT II treaty limitations in anticipation of the introduction of the Ohio class submarines in the early 1980s, a decision was made to repurpose these vessels.

Consequently, in 1981, they were retired from their Fleet Ballistic Missile (FBM) roles. Each submarine was redesignated and converted into an attack submarine, or SSN, which necessitated the decommissioning of their missile tubes and removal of their missile fire control systems, thus marking their new era as “slow attacks” as they were nicknamed.

Special Operations submarines

From September 1983 to September 1985, Sam Houston and John Marshall underwent modifications at the Puget Sound Naval Shipyard to be repurposed as ‘Amphibious Transports’ for special operations.

Both vessels were equipped with Dry Deck Shelters (DDS), serving as housing for SEAL team swimmer vehicles, and as entry and exit points for the SEAL teams. The DDS canisters were installed on the upper decking of the two submarines, just aft of the sail.

The John Marshall (SSBN 611) reconfigured as an SSN with two Dry Deck Shelters (DDS) used to transport Special Forces.
The John Marshall (SSBN 611) reconfigured as an SSN with two Dry Deck Shelters (DDS) used to transport Special Forces. (U.S. Navy photo via Al Adcock)

In addition, the alterations included the addition of extra berthing spaces for up to 67 commandos, the removal of some missile tube bases, and the conversion of others into air-locks and storage spaces for equipment. The estimated operational life of these converted vessels extended into the late 1990s, with a diving depth of 300 meters (984 feet).


The decommissioning process for the Ethan Allen Class submarines began with the USS Ethan Allen on March 31, 1983, making it the first submarine of the class to retire. Its recycling was completed by July 30, 1999, and certain parts of its hull containing nuclear reactor components can now be seen in Hanford, WA.

No.NameRec. SSNDecommStrickenBroken up
SSBN 608Ethan Allen1 Sep 198031 Mar 19832 Apr 19831999
SSBN 609Sam Houston10 Nov 19806 Sep 19916 Sep 19911992
SSBN 610Thomas A. Edison6 Oct 19801 Dec 198330 Apr 19861997
SSBN 611John Marshall20 Jun 198122 Jul 199222 Jul 19921993
SSBN 618Thomas Jefferson20 Nov 198024 Jan 198530 Apr 19861998

The last submarine of this class was retired from service in 1992. The process of recycling and scrapping these submarines occurred from 1992 until 1999.

The sail from the USS Thomas Jefferson (SSBN-618) at Gosport Park, located just a few blocks from Norfolk Naval Shipyard in Portsmouth, Virginia
The sail from the USS Thomas Jefferson (SSBN-618) at Gosport Park, located just a few blocks from Norfolk Naval Shipyard in Portsmouth, Virginia. (Naval History and Heritage Command)

In Tom Clancy’s book, “The Hunt for Red October,” the retired USS Ethan Allen is destroyed as a diversion, enabling the rogue Soviet submarine, Red October, to evade capture.

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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