The Permit-class submarine (known as the Thresher class until the lead boat was lost) was a class of fourteen nuclear-powered fast attack submarines (hull classification symbol SSN) in service with the United States Navy from the early 1960s until 1996. They were a significant improvement on the , with greatly improved sonar, diving depth, and silencing. They were followed by the and classes.

The Thresher class was one of several results from a study commissioned in 1956 by Chief of Naval Operations (CNO) Admiral Arleigh Burke. In "Project Nobska", the Committee on Undersea Warfare of the United States National Academy of Sciences, collaborating with numerous other agencies, considered the lessons of submarine warfare and anti-submarine warfare learned from various prototypes and experimental platforms. The design was managed under project SCB 188.

Design

The new class kept the proven S5W reactor plant from the immediately preceding s, but were a radical change in many other ways. The Threshers had the large bow-mounted sonar sphere and angled, amidships torpedo tubes used in the concurrently-built . This placed the sonar sphere in the optimum position for detection of targets at long range. Tullibee was an alternate design optimized for anti-submarine warfare, much smaller and slower than the Threshers and with a quiet turbo-electric propulsion system. Although they used the same HY-80 steel (yield strength ) as the Skipjacks, the Threshers pressure hulls were made using an improved design that extended test depth to . The engineering spaces were also redesigned, with the turbines supported on "rafts" that were suspended from the hull on isolation mounts for acoustic quieting. Drag was reduced, with external fittings kept to a minimum and the sail greatly reduced in size. However, the small sail had disadvantages as well, including room for only one periscope and a reduced number of electronics masts, less convenient surfaced operation in rough seas, and an increased possibility of "broaching" (inadvertent surfacing) at periscope depth in rough seas.

Only Thresher was fitted with a five-bladed symmetric screw, very similar to the ones originally fitted to the Skipjacks, which allowed her to reach this speed. During trials of the Skipjack class, it was found that the propeller produced noise below cavitation depth. It was determined that the source of this noise, called blade-rate, was the blades of the screw vibrating when they hit the wake of the sail and control surfaces.

Construction

The first submarine commissioned in the class was the ill-fated , and so the class was known by her name. When Thresher was lost on 10 April 1963, the class took the name of the second ship in the class, . Thresher had numerous advanced design features and embodied the future of US Navy submarine design, and her loss was a serious blow. As a result, the SUBSAFE program was instituted to correct design flaws and introduce strict manufacturing and construction quality control in critical systems. The seawater and main ballast systems of future classes (Sturgeon-class SSNs and SSBNs) were redesigned, and some Threshers and other submarines were rebuilt to SUBSAFE standards. SUBSAFE includes specific training of SUBSAFE quality assurance inspectors in the engineering crew, and tracks extremely detailed information about every component of a submarine that is subject to sea pressure. Joints in any equipment carrying seawater must be welded (not brazed), and every hull penetration larger than a specified size can be quickly shut by a remote hydraulic mechanism.

{| class="wikitable sortable"

!Name

! width=50px | Hull number

! width=200px | Builder

!

!

!

!

!Period<br /> of<br /> service

! colspan=2 | Fate

|-

|

|SSN-593

|Portsmouth Naval Shipyard

|28 May 1958

|9 Jul 1960

|3 Aug 1961

|

|1.7

| width=90px |10 Apr 1963

| Lost with 129 crewmembers and shipyard personnel east of Cape Cod, Massachusetts, exact cause unknown.

|-

|

|SSN-594

|rowspan=2|Mare Island Naval Shipyard

|16 Jul 1959

|1 Jul 1961

|29 May 1962

|12 Jun 1991

|29.0

|20 May 1993 || Disposed

|-

|

|SSN-595

|2 Mar 1960

|9 Dec 1961

|21 Nov 1962

|3 Jan 1990

|27.0

| 8 Mar 1996 || Disposed

|-

|

|SSN-596

|Ingalls Shipbuilding, Pascagoula, Mississippi

|9 Nov 1959

|11 Feb 1962

|24 Aug 1963

|20 Dec 1989

|26.3

|14 Mar 1996 || Disposed

|-

|

|SSN-603

|rowspan=2|New York Shipbuilding, Camden, New Jersey

|14 Mar 1960

|17 Mar 1962

|26 May 1964

|1 Mar 1989

|24.8

|17 Feb 1995|| Disposed

|-

|

|SSN-604

|9 Sep 1960

|18 Aug 1962

|16 Dec 1964

|12 Jun 1991

|26.4

| 20 Jun 1992 || Disposed

|-

|

|SSN-605

|rowspan=2|Portsmouth Naval Shipyard

|16 Sep 1960

|24 Apr 1963

|31 Mar 1967

|11 Jul 1990

|23.3

|30 Jun 1992 || Disposed

|-

|

|SSN-606

|24 Nov 1959

|9 Dec 1961

|17 Oct 1964

|15 Jan 1992

|27.3

|15 Aug 1992 || Disposed

|-

|

|SSN-607

|Ingalls Shipbuilding, Pascagoula, Mississippi

|6 Jun 1960

|18 Aug 1962

|4 Apr 1964

|2 Dec 1988

|24.7

|1 Jan 1997 || Disposed

|-

|

|SSN-612

|New York Shipbuilding, Camden, New Jersey

|13 Feb 1961

|15 May 1965

|20 Dec 1966

|2 Feb 1992

|25.0

|9 Jul 1992 || Disposed

|-

|

|SSN-613

|rowspan=3|Electric Boat

|14 Apr 1961

|22 Jun 1963

|22 Jul 1966

|26 May 1992

|25.8

| 11 May 1994 || Disposed

|-

|

|SSN-614

|15 Aug 1961

|4 Apr 1964

|3 Nov 1967

|18 Apr 1994

|26.4

|30 Sep 1994 || Disposed

|-

|

|SSN-615

|15 Dec 1961

|14 May 1964

|25 Jan 1968

|25 Apr 1996

|28.2

| || Disposed

|-

|

|SSN-621

|Ingalls Shipbuilding, Pascagoula, Mississippi

|24 Apr 1961

|21 May 1966

|22 Dec 1967

|7 Apr 1993

|25.3

| || Disposed

|-

| colspan=10 |

|}

See also

  • List of submarines of the United States Navy
  • List of submarine classes of the United States Navy

References

  • Gardiner, Robert and Chumbley, Stephen, Conway's All the World's Fighting Ships 1947–1995, London: Conway Maritime Press, 1995. .
  • Karam, P. Andrew and Thompson, Roger, Rig Ship for Ultra Quiet: Life on a nuclear attack boat at the end of the Cold War. Google Books link
  • Hutchinson, Robert, Jane's Submarines, War Beneath The Waves, From 1776 To The Present Day, Harper Paperbacks, 2005. .
  • Polmar, Norman (2004). Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines, 1945-2001. Dulles: Brassey's. .
  • On Eternal Patrol USS Thresher page
  • NavSource SSN Photo Gallery Index
  • SSN-594 Permit class at GlobalSecurity.org