View source for Permit-class submarine

{{Short description|US Navy fast attack submarines}}
{|{{Infobox ship begin}}
{{Infobox ship image
|Ship image=USS Thresher (SSN-593) bow.jpg
|Ship caption= USS ''Thresher'' (SSN-593)
}}
{{Infobox ship class overview
|Name=
|Builders=*[[Portsmouth Naval Shipyard]]
*[[Mare Island Naval Shipyard]]
*[[Ingalls Shipbuilding]]
*[[New York Shipbuilding]]
*[[General Dynamics Electric Boat]]
|Operators={{naval|United States}}
|Class before={{sclass|Skipjack|submarine|4}}
|Class after={{sclass|Sturgeon|submarine|4}}
|Subclasses=
|Cost=
|Built range=1958–1967
|In service range=   
|In commission range=1961–1996
|Total ships building= 
|Total ships planned=
|Total ships completed=14
|Total ships cancelled=
|Total ships active=
|Total ships laid up=
|Total ships lost=1
|Total ships retired=13
|Total ships preserved=
}}
{{Infobox ship characteristics
|Hide header=
|Header caption= 
|Ship type=[[Nuclear submarine]]
|Ship displacement=*{{convert|3750|LT|t|0|lk=in|abbr=on}} surfaced
*{{convert|4300|LT|t|0|abbr=on}} submerged<ref name="FriedmanSubs1">{{cite book | last = Friedman | first = Norman | title = U.S. Submarines Since 1945: An Illustrated Design History | publisher = [[United States Naval Institute]] | year = 1994 | location = [[Annapolis, Maryland]] | pages = 141–46, 243 | isbn = 1-55750-260-9 }}</ref>
|Ship length= {{convert|278|ft|5|in|m|abbr=on}}
|Ship beam= {{convert|31|ft|7|in|m|abbr=on}}
|Ship draft= {{convert|25|ft|2|in|m|abbr=on}}
|Ship depth=
|Ship decks=
|Ship deck clearance=
|Ship power=
|Ship propulsion=*1 [[S5W reactor|S5W]] [[Pressurized water reactor|PWR]]
*2 steam turbines, {{convert|15000|shp|MW|0|abbr=on}}
*1 shaft
|Ship speed=*{{convert|15|kn|lk=in}} surfaced
*{{convert|28|kn}}  submerged 
|Ship range=Unlimited, except by food supplies
|Ship endurance=
|Ship test depth= {{convert|1300|ft|m|abbr=on}}
|Ship complement=112
|Ship time to activate=
|Ship sensors=*BQQ-2 [[sonar]] (later BQQ-5)
*Mark 113 [[Fire-control system]] (later Mark 117)
*[[Periscope]]s
|Ship EW= ESM
|Ship armament=*4 × [[American 21 inch torpedo|21 inch (533 mm)]] [[torpedo tube]]s amidships
*12-18 × [[Mark 37 torpedo]]es, later replaced by [[Mark 48 torpedo|Mark 48s]]
*4-6 × [[UUM-44 SUBROC]] anti-submarine missiles
*4 × [[UGM-84 Harpoon]] anti-ship missiles
|Ship armor=
|Ship notes=
}}
|}
The '''''Permit''-class submarine''' (known as the '''''Thresher'' class''' until the lead boat {{USS|Thresher|SSN-593|6}} was lost) was a class of [[Nuclear marine propulsion|nuclear-powered]] fast [[attack submarine]]s ([[Hull classification symbol#Submarine type|hull classification symbol]] SSN) in service with the [[United States Navy]] from the early 1960s until 1996. They were a significant improvement on the {{sclass|Skipjack|submarine|4}}, with greatly improved [[sonar]], diving depth, and silencing.<ref name="FriedmanSubs1"/> They were the forerunners of all subsequent US Navy SSN designs. They served from the 1960s through to the early 1990s, when they were decommissioned due to age.<ref>Friedman, pp. 235–36</ref> They were followed by the {{sclass|Sturgeon|submarine|5}} and {{sclass|Los Angeles|submarine|5}} 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 [[Ship Characteristics Board|SCB 188]].<ref>Friedman, p. 143</ref>

==Design==
The new class kept the proven [[S5W reactor]] plant from the immediately preceding {{sclass|Skipjack|submarine|5}}s, but were a radical change in many other ways.  The ''Thresher''s had the large [[Bow (ship)|bow]]-mounted [[sonar]] sphere and angled, amidships [[torpedo tube]]s used in the concurrently-built {{USS|Tullibee|SSN-597|2}}. 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 ''Thresher''s and with a quiet [[turbo-electric transmission|turbo-electric propulsion]] system.<ref>Friedman, pp. 136–42, 243</ref> Although they used the same [[HY-80]] steel ([[yield strength]] {{convert|80000|psi|MPa|abbr=on}}) as the ''Skipjack''s, the ''Thresher''s{{'}} [[pressure hull]]s were made using an improved design that extended test depth to {{convert|1,300|ft|m|abbr=on}}. 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 (submarine)|sail]] greatly reduced in size.<ref name="FriedmanSubs1"/>

The small sail of ''Thresher'' (the smallest fitted to an American SSN) compensated for the increased drag of the longer hull, giving ''Thresher'' a top speed of {{convert|33|kn|lk=in}}, the same as the ''Skipjack''s, according to one recollection.<ref>Polmar, Norman; Moore, K. J. (2004) ''Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines'', Potomac Books, p. 363</ref> 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.<ref name="Friedman, pp. 143-146">Friedman, pp. 143–46</ref>

Only ''Thresher'' was fitted with a five-bladed symmetric [[Propeller|screw]], very similar to the ones originally fitted to the ''Skipjack''s, which allowed her to reach this speed. During [[Sea trials|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.<ref name="FriedmanSubs1"/> This produced a noise that could carry for many miles and could be used by an enemy submarine to set up a firing solution because the frequency of blade-rate was directly related to the speed of the submarine (the RPM of the screw).  The solution was to either make the screw smaller so it did not hit the wakes of the sail and control surfaces, which would cavitate more easily because of its increased speed, or have a large screw that gently interacted with these areas of disturbed water.  The latter solution was chosen for all subsequent American SSNs.  ''Permit'' and later submarines of this class had seven-bladed skewback screws, which reduced the problem of blade-rate, but reduced the submarines' top speed to {{convert|29|-|28|kn}}.  ''Jack'' was designed with counter-rotating screws, each of which were smaller than the standard seven-bladed screw, as an alternative solution to the blade-rate problem.<ref name="FriedmanSubs1"/>

The class received mid-life upgrades in the late 1970s and 1980s, including the {{Interlanguage link|AN/BQQ-5|uk|AN/BQQ-5}} sonar suite with a retractable [[towed array sonar|towed array]], Mk 117 torpedo fire control equipment, and other electronics upgrades.{{citation_needed|date=August 2019}}

==Armament==
The boats had their torpedo tubes moved to the middle of the hull and angled outboard.  This made available the required large space in the bow for the BQQ-2 (BQQ-5 as modernized from the late 1970s) sonar sphere, a new and powerful low-frequency detection sensor. Initially armed with [[Mark 37 torpedo]]es, by the late 1960s they carried the improved [[Mark 48 torpedo|Mark 48]] and the nuclear [[UUM-44 SUBROC]] short-range anti-submarine missile, replacing up to six Mk 48s. The ''Thresher''s were the first class fitted with the Mark 113 fire control system that enabled the use of SUBROC; they were later upgraded with the Mark 117 system. In the late 1970s the [[UGM-84 Harpoon]] [[anti-ship missile]] was introduced; typically four were carried in place of Mk 48s.{{citation_needed|date=August 2019}}

The maximum weapons load was 23 torpedoes/missiles or, theoretically, up to 42 Mk 57, Mk 60, or Mk 67 [[Naval mine|mines]]. Any mix of mines, torpedoes, and missiles could be included.<ref>''War Machines Encyclopedia'', Aerospace Publishing Ltd., Italian version printed by De Agostini, pp. 526–27</ref>

==Construction==
The first submarine commissioned in the class was the ill-fated {{USS|Thresher|SSN-593|2}}, 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, {{USS|Permit|SSN-594|2}}. ''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 {{sclass|Benjamin Franklin|submarine|0}} [[SSBN]]s) were redesigned, and some ''Thresher''s 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 [[Welding|welded]] (not [[Brazing|brazed]]), and every hull penetration larger than a specified size can be quickly shut by a remote hydraulic mechanism.<ref name="Friedman, pp. 143-146"/> The program has been very successful, as no SUBSAFE submarines have been lost as of 2023 ({{USS|Scorpion|SSN-589|2}} was not SUBSAFE).{{citation_needed|date=August 2019}}

{{USS|Flasher|SSN-613|2}}, {{USS|Greenling|SSN-614|2}}, and {{USS|Gato|SSN-615|2}} were designed under project SCB 188M and were fitted with a larger sail, to house additional masts, and built 13 feet 9 inches longer than the other units of the class to include more SUBSAFE features, additional reserve buoyancy, more intelligence gathering equipment and improved accommodations. {{USS|Haddock|SSN-621|2}} was completed with the larger sail but the standard {{convert|279|ft|m|adj=on}} hull.

The engine room of {{USS|Jack|SSN-605|2}} was lengthened by {{convert|10|ft|m}} to accommodate an experimental [[direct drive|direct-drive]] propulsion system using concentric counter-rotating propellers.  Although counter-rotating propellers produced impressive gains in speed on the experimental {{USS|Albacore|AGSS-569|2}}, in ''Jack'' the results were disappointing because of the difficulty in sealing the shaft.  ''Jack'' was also used to test polymer ejection that could reduce flow noises that degraded sonar performance.{{citation_needed|date=August 2019}}

==Boats in class==
The gaps in the hull number sequence were taken by the unique {{USS|Tullibee|SSN-597|2}}, and the {{sclass|George Washington|submarine|5}}, {{sclass|Ethan Allen|submarine|5}}, and {{sclass|Lafayette|submarine|0}} fleet ballistic missile submarine classes.{{citation_needed|date=August 2019}}

{| class="wikitable" style="font-size:97%;"
!Name
!Hull number
! width="20%" | Builder
!Laid Down
!Launched
!Commissioned
!Decommissioned
!Period of service
! width="35%" | Fate
|-
|{{USS|Thresher|SSN-593|2}}
|SSN-593
|[[Portsmouth Naval Shipyard]]
|28 May 1958
|9 July 1960
|3 August 1961
|{{n/a}}
|1.7
|Lost with 129 crewmembers and shipyard personnel on 10 April 1963, {{convert|200|nmi|km}} east of [[Cape Cod]], [[Massachusetts]], exact cause unknown.
|-
|{{USS|Permit|SSN-594|2}}
|SSN-594
|rowspan=2|[[Mare Island Naval Shipyard]]
|16 July 1959
|1 July 1961
|29 May 1962
|12 June 1991
|29.0
|Recycled via the nuclear [[Ship and Submarine Recycling Program]] 20 May 1993.
|-
|{{USS|Plunger|SSN-595|2}}
|SSN-595
|2 March 1960
|9 December 1961
|21 November 1962
|3 January 1990
|27.0
|Recycled via the nuclear Ship and Submarine Recycling Program 8 March 1996.
|-
|{{USS|Barb|SSN-596|2}}
|SSN-596
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|9 November 1959
|11 Feb 1962
|24 August 1963
|20 December 1989
|26.3
|Recycled via the nuclear Ship and Submarine Recycling Program 14 March 1996.
|-
|{{USS|Pollack|SSN-603|2}}
|SSN-603
|rowspan=2|[[New York Shipbuilding]], [[Camden, New Jersey]]
|14 March 1960
|17 March 1962
|26 May 1964
|1 March 1989
|24.8
|Recycled via the nuclear Ship and Submarine Recycling Program 17 February 1995.
|-
|{{USS|Haddo|SSN-604|2}}
|SSN-604
|9 September 1960
|18 August 1962
|16 December  1964
|12 June 1991
|26.4
|Recycled via the nuclear Ship and Submarine Recycling Program 20 June 1992.
|-
|{{USS|Jack|SSN-605|2}}
|SSN-605
|rowspan=2|[[Portsmouth Naval Shipyard]]
|16 September 1960
|24 April 1963
|31 March 1967
|11 July 1990
|23.3
|Recycled via the nuclear Ship and Submarine Recycling Program 30 June 1992.
|-
|{{USS|Tinosa|SSN-606|2}}
|SSN-606
|24 November 1959
|9 December 1961
|17 October 1964
|15 January 1992
|27.3
|Recycled via the nuclear Ship and Submarine Recycling Program 15 August 1992.
|-
|{{USS|Dace|SSN-607|2}}
|SSN-607
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|6 June 1960
|18 August 1962
|4 April 1964
|2 December 1988
|24.7
|Recycled via the nuclear Ship and Submarine Recycling Program 1 January 1997.
|-
|{{USS|Guardfish|SSN-612|2}}
|SSN-612
|[[New York Shipbuilding]], [[Camden, New Jersey]]
|13 February 1961
|15 May 1965
|20 December 1966
|2 February 1992
|25.0
|Recycled via the nuclear Ship and Submarine Recycling Program 9 July 1992.
|-
|{{USS|Flasher|SSN-613|2}}
|SSN-613
|rowspan=3|[[Electric Boat]]
|14 April 1961
|22 June 1963
|22 July 1966
|26 May 1992
|25.8
|Recycled via the nuclear Ship and Submarine Recycling Program 11 May 1994.
|-
|{{USS|Greenling|SSN-614|2}}
|SSN-614
|15 August 1961
|4 April 1964
|3 November 1967
|18 April 1994
|26.4
|Recycled via the nuclear Ship and Submarine Recycling Program 30 September 1994.
|-
|{{USS|Gato|SSN-615|2}}
|SSN-615
|15 December 1961
|14 May 1964
|25 January 1968
|25 April 1996
|28.2
|Recycled via the nuclear Ship and Submarine Recycling Program.
|-
|{{USS|Haddock|SSN-621|2}}
|SSN-621
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|24 April 1961
|21 May 1966
|22 December 1967
|7 April 1993
|25.3
|Recycled via the nuclear Ship and Submarine Recycling Program.
|-
|}

==See also==
* [[List of submarines of the United States Navy]]
* [[List of submarine classes of the United States Navy]]
* [[Ship Characteristics Board#USS Thresher loss|Ship Characteristics Board – USS ''Thresher'' loss]]

==References==
{{reflist|30em}}
* Gardiner, Robert and Chumbley, Stephen, ''Conway's All the World's Fighting Ships 1947–1995'', London: Conway Maritime Press, 1995. {{ISBN|1-55750-132-7}}.
* Karam, P. Andrew and Thompson, Roger, ''Rig Ship for Ultra Quiet: Life on a nuclear attack boat at the end of the Cold War''. [https://books.google.com/books?id=ML_BAAAACAAJ&q=rig+ship+for+ultra+quiet Google Books link]
* Hutchinson, Robert, ''Jane's Submarines, War Beneath The Waves, From 1776 To The Present Day'', Harper Paperbacks, 2005. {{ISBN|0-06081-900-6}}.
* Polmar, Norman (2004). ''Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines, 1945-2001''. Dulles: Brassey's. {{ISBN|978-1-57488-594-1}}.

==External links==
{{Commons category|Thresher/Permit class submarines}}
* [http://www.oneternalpatrol.com/uss-thresher-593.htm On Eternal Patrol USS ''Thresher'' page]
* [http://www.navsource.org/archives/08/05idx.htm NavSource.org SSN Photo Gallery Index]
* [http://www.globalsecurity.org/military/systems/ship/ssn-594.htm SSN-594 Permit class] at GlobalSecurity.org

{{Permit class submarine}}
{{US submarine classes after 1945}}

{{DEFAULTSORT:Permit Class Submarine}}
[[Category:Submarine classes]]
[[Category:Permit-class submarines| ]]
[[Category:Cold War submarines of the United States| Permit class]]
[[Category:Vietnam War submarines of the United States| Permit class]]
[[Category:1960s ships]]