View source for Permit-class submarine

{{Short description|US Navy fast attack submarines}}
{{Infobox ship
|section1={{Infobox ship/image
 |image=USS Thresher (SSN-593) bow.jpg
 |image_caption= USS ''Thresher'' (SSN-593)
 }}

|section2={{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_canceled=
 |total_ships_active=
 |total_ships_laid_up=
 |total_ships_lost=1
 |total_ships_retired=13
 |total_ships_preserved=
 }}

|section3={{Infobox ship/characteristics
 |hide_header=
 |header_caption= 
 |type=[[Nuclear submarine]]
 |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>
 |length= {{convert|278|ft|5|in|m|abbr=on}}
 |beam= {{convert|31|ft|7|in|m|abbr=on}}
 |draft= {{convert|25|ft|2|in|m|abbr=on}}
 |depth=
 |decks=
 |deck_clearance=
 |power=
 |propulsion=*1 [[S5W reactor|S5W]] [[Pressurized water reactor|PWR]]
             *2 steam turbines, {{convert|15000|shp|MW|0|abbr=on}}
             *1 shaft
 |speed=*{{convert|15|kn|lk=in}} surfaced
        *{{convert|28|kn}}  submerged 
 |range=Unlimited, except by food supplies
 |endurance=
 |test_depth= {{convert|1300|ft|m|abbr=on}}
 |complement=112
 |time_to_activate=
 |sensors=*BQQ-2 [[sonar]] (later BQQ-5)
          *Mark 113 [[Fire-control system]] (later Mark 117)
          *[[Periscope]]s
 |EW= ESM
 |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
 |armor=
 |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 fourteen [[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 (watercraft)|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 sortable" 
!Name
! width=50px | Hull number
! width=200px | Builder
! {{vert header|Laid Down|mw=90px}}
! {{vert header|Launched|mw=90px}}
! {{vert header|Commissioned|mw=90px}}
! {{vert header|Decommissioned|mw=90px}}
!Period<br /> of<br /> service
! colspan=2 | Fate
|-
|{{USS|Thresher|SSN-593|2}}
|SSN-593
|[[Portsmouth Naval Shipyard]]
|28 May 1958
|9 Jul 1960
|3 Aug 1961
|{{n/a}}
|1.7
| width=90px |10 Apr 1963 
| Lost with 129 crewmembers and shipyard personnel {{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 Jul 1959
|1 Jul 1961
|29 May 1962
|12 Jun 1991
|29.0
|20 May 1993 || Disposed{{efn|name=SSRP|Recycled via the nuclear [[Ship-Submarine Recycling Program]].}}
|-
|{{USS|Plunger|SSN-595|2}}
|SSN-595
|2 Mar 1960
|9 Dec 1961
|21 Nov 1962
|3 Jan 1990
|27.0
| 8 Mar 1996 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Barb|SSN-596|2}}
|SSN-596
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|9 Nov 1959
|11 Feb 1962
|24 Aug 1963
|20 Dec 1989
|26.3
|14 Mar 1996 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Pollack|SSN-603|2}}
|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{{efn|name=SSRP}}
|-
|{{USS|Haddo|SSN-604|2}}
|SSN-604
|9 Sep 1960
|18 Aug 1962
|16 Dec  1964
|12 Jun 1991
|26.4
| 20 Jun 1992 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Jack|SSN-605|2}}
|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{{efn|name=SSRP}}
|-
|{{USS|Tinosa|SSN-606|2}}
|SSN-606
|24 Nov 1959
|9 Dec 1961
|17 Oct 1964
|15 Jan 1992
|27.3
|15 Aug 1992 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Dace|SSN-607|2}}
|SSN-607
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|6 Jun 1960
|18 Aug 1962
|4 Apr 1964
|2 Dec 1988
|24.7
|1 Jan 1997 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Guardfish|SSN-612|2}}
|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{{efn|name=SSRP}}
|-
|{{USS|Flasher|SSN-613|2}}
|SSN-613
|rowspan=3|[[Electric Boat]]
|14 Apr 1961
|22 Jun 1963
|22 Jul 1966
|26 May 1992
|25.8
| 11 May 1994 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Greenling|SSN-614|2}}
|SSN-614
|15 Aug 1961
|4 Apr 1964
|3 Nov 1967
|18 Apr 1994
|26.4
|30 Sep 1994 || Disposed{{efn|name=SSRP}}
|-
|{{USS|Gato|SSN-615|2}}
|SSN-615
|15 Dec 1961
|14 May 1964
|25 Jan 1968
|25 Apr 1996
|28.2
| || Disposed{{efn|name=SSRP}}
|-
|{{USS|Haddock|SSN-621|2}}
|SSN-621
|[[Ingalls Shipbuilding]],  [[Pascagoula, Mississippi]]
|24 Apr 1961
|21 May 1966
|22 Dec 1967
|7 Apr 1993
|25.3
| || Disposed{{efn|name=SSRP}}
|-
| colspan=10 | {{notelist}}
|}

==See also==
* [[List of submarines of the United States Navy]]
* [[List of submarine classes of the United States Navy]]
* {{slink|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.net/archives/08/05idx.htm NavSource 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]]