The Grayback-class submarine was a class of two guided missile-carrying submarines of the United States Navy. They carried the Regulus I and Regulus II nuclear cruise missiles, deployed 1957–64, that were rapidly phased out by Polaris Submarine Launched Ballistic Missiles (SLBMs). They and USS Halibut were the sole submarines designed specifically to carry Regulus missiles, and the only submarines capable of carrying Regulus II. However, USS Tunny and USS Barbero were modified earlier to carry two Regulus I missiles per boat.

Quick Facts Class overview, General characteristics ...

Grayback preparing to launch a Regulus II missile, c. 1960
Class overview
Name	Grayback
Operators	United States Navy
Preceded by	Tang-class
Built	1954–1958
In commission	1958–1964, 1969–1984
Completed	2
Retired	1
Preserved	1
General characteristics
Type	Submarine
Tonnage	Surfaced: 2712 tonnes (2670 tons) Submerged: 3708 tonnes (3650 tons)
Displacement	2,768 long tons (2,812 t) full
Length	317 ft 7 in (96.80 m)
Beam	27 ft 2 in (8.28 m)
Draft	19 ft (5.8 m)
Propulsion	3 × Fairbanks-Morse Diesel engines (total 4,500 shp (3,400 kW)),[1] 2 × Elliott electric motors (total 5,500 shp (4,100 kW)),[1] 4 × 126-cell GUPPY I batteries,[2] 2 shafts
Speed	15 knots (28 km/h; 17 mph) surfaced, 12 knots (22 km/h; 14 mph) submerged
Test depth	700 ft (210 m)[2]
Complement	84
Armament	2 × Regulus missile hangars (4 × Regulus I missiles or 2 × Regulus II missiles) 8 × 21 inch (533 mm) torpedo tubes (6 bow, 2 stern)

Close

On the Graybacks, two missile hangars allowed for a total of two Regulus II or four Regulus I missiles each. Since Regulus II was cancelled in December 1958 except for test firings,^[3] the class deployed with four Regulus I missiles. They were originally ordered as sisters of USS Darter, similar to the last Tang-class submarines, but were converted under project SCB 161 to missile submarines during construction.^[4][2] Torpedo armament was the same as the Tangs, with six bow and two stern tubes. The stern tubes were for "swim-out" weapons only, such as the Mark 37 ASW homing torpedo.

In Grayback's later role as an amphibious transport submarine, the former missile hangars were used to store SEAL Swimmer Delivery Vehicles and other equipment used by the SEALs and Marine Force Recon units.

• Grayback (SSG-574), launched 1957, served as a missile submarine 1958–1964, converted to an amphibious transport submarine (hull classification symbol LPSS) (initially transport submarine (APSS)) and served as such 1969–1984. Sunk as a target near Subic Bay, Philippines, 13 April 1986.
• Growler (SSG-577), launched 1958, served 1958–1964. Museum ship at the Intrepid Sea-Air-Space Museum in New York City from 29 September 1988.