View source for SSM-N-8 Regulus

{{Short description|US Navy cruise missile}}
{{Use dmy dates|date=June 2017}}
{{More footnotes needed|date=April 2009}}
{{Infobox weapon
| is_missile         = yes
| name               = SSM-N-8 Regulus
| image              = Vought SSM-N-8 Regulus I (ID unknown) (30571413366).jpg
| image_size         = 300
| caption            = SSM-N-8 Regulus I on display at the [[Intrepid Sea, Air & Space Museum]]
| origin             = United States
| type               = [[Cruise missile]]
| used_by            = United States Navy
| manufacturer       = [[Vought|Chance Vought]]
| unit_cost          = 
| propellant         = 
| production_date    = March 1951
| service            = 1955-64
| engine             = [[Allison J33]]-A-14 turbojet {{convert|4600|lbf|kN|abbr=on}}<br />2 × [[JATO|booster rockets]]  {{convert|33000|lbf|kN|abbr=on}}
| engine_power       = 
| weight             = {{convert|13685|lb|kg}}
| length             = {{convert|32|ft|2|in|m}}
| diameter           = {{convert|4|ft|8.5|in|m}}
| wingspan           = {{convert|21|ft|m}} extended<br />{{convert|9|ft|10.5|in|m}} folded
| speed              = Subsonic
| vehicle_range      = {{convert|500|nmi|km|0}}
| ceiling            = 
| altitude           = 
| filling            = {{convert|3000|lb|kg}} such as the [[Mark 5 nuclear bomb|W5 warhead]] or the [[Mark 27 nuclear bomb|W27 warhead]]
| guidance           = radio-command by ground stations, aircraft, or ships along the flight path
| detonation         = 
| launch_platform    = 
}}

The '''SSM-N-8A Regulus''', also known as the '''Regulus I''' and '''RGM-6''', is a  nuclear-capable [[turbojet]]-powered second generation [[cruise missile]] operated by the US Navy between 1955 and 1964. Its development was an outgrowth of U.S. Navy tests conducted with the German [[V-1 missile]] at [[Naval Air Station Point Mugu]] in California.<ref>[http://www.public.navy.mil/subfor/underseawarfaremagazine/Issues/PDF/USW_Spring_2001.pdf ''Regulus: America's First Sea-borne Nuclear Deterrent''] {{Webarchive|url=https://web.archive.org/web/20170211231915/http://www.public.navy.mil/subfor/underseawarfaremagazine/Issues/PDF/USW_Spring_2001.pdf |date=11 February 2017 }} Edward C. Whitman. ''Undersea Warfare'' vol. 3 no. 3., pp 31.</ref> Its barrel-shaped fuselage resembled that of numerous fighter aircraft designs of the era, but without a cockpit. Test articles of the Regulus were equipped with landing gear and could take off and land like an airplane.<ref name="ReferenceA">''Regulus: The First Nuclear Missile Submarines'' documentary, Spark, 2002</ref> When the missiles were deployed they were launched from a rail launcher, and equipped with a pair of [[Aerojet]] [[JATO]] bottles on the aft end of the fuselage.

==History==
===Design and development===

==== Background ====
Nazi Germany's use of the [[V-1 flying bomb]] during [[World War II]] marked the first combat deployment of a [[cruise missile]], highlighting the potential of a new class of weapon.<ref>{{Cite web |date=1980-12-01 |title=The Birth of Guided Missiles |url=https://www.usni.org/magazines/proceedings/1980/december/birth-guided-missiles |access-date=2025-03-03 |website=U.S. Naval Institute |language=en}}</ref> Even before [[German Instrument of Surrender|Germany's surrender]], the United States captured, [[Reverse engineering|reverse-engineered]], and [[Mass production|mass-produced]] its own version of the V-1, the [[Republic-Ford JB-2|Republic-Ford JB-2 Loon]], intended for use against [[Empire of Japan|Japan]]. With the war's end and the onset of the [[Cold War]], the U.S. sought new ways to deploy [[Nuclear weapon|nuclear warheads]]. One proposal, put forward by Captain [[Thomas B. Klakring|Thomas Klakring]], was to launch nuclear missiles from submarines. He argued that submarines would be far more difficult to detect and attack than surface ships, such as [[Aircraft carrier|aircraft carriers]], while also introducing a new method of warhead delivery beyond [[aircraft]]. At the time, [[Bomber|bombers]] were the U.S. military's only means of delivering nuclear warheads, a reliance that threatened to diminish the Navy's role and overemphasize a single approach to nuclear strategy.<ref name=":0">{{Cite web |date=1993-04-01 |title=Blasts from the Past |url=https://www.usni.org/magazines/proceedings/1993/april/blasts-past |access-date=2025-03-03 |website=U.S. Naval Institute |language=en}}</ref><ref>{{Cite web |date=2022-11-04 |title=Battle Stations Missile! |url=https://www.usni.org/magazines/naval-history-magazine/2003/august/battle-stations-missile |access-date=2025-03-03 |website=U.S. Naval Institute |language=en}}</ref>

Klakring proposed launching the Loon from submarines to test his concept. Work began in 1946, and by 1947, [[USS Cusk|USS ''Cusk'']] became the first U.S. submarine to fire a guided missile. Testing continued for several years, but significant issues arose. ''Cusk'' nearly sank when a Loon exploded on deck, and the missile itself was slow, had limited range and payload, and was impractical for military use. Despite these shortcomings, the tests successfully demonstrated how a submarine could surface, launch a missile, and submerge again, making it difficult for an enemy to retaliate. The Navy acknowledged the concept’s potential but recognized the need for a missile specifically designed for submarine deployment.<ref name=":0" />

==== Development ====
Development of such a missile began with [[Grumman]]'s [[SSM-N-6 Rigel]] and the [[Applied Physics Laboratory|Johns Hopkins Applied Physics Laboratory's]] [[SSM-N-2 Triton]]. However, work did not begin in earnest until August of 1947, days after the [[United States Army Air Forces|United States Army Air Force]] awarded a contract for the ground-based [[MGM-1 Matador]] [[cruise missile]]. The Navy, not wanting to lose its edge in missile development, began Project Regulus with the same equipment used in the Matador. On  17 November 1947, a contract was awarded to Chance Vought, which previously investigated a similar project as part of a study on "pilotless missiles". The company, desperate for government contracts as the money-making [[Vought F4U Corsair|F4U Corsair]] production line was nearing an end, focused on a practical design that could be brought into service quickly. With its survival at stake, the company invested heavily in [[research and development]], drawing from experience with jet fighter projects such as the [[Vought XF5U|XF5U Flying Flapjack]], [[Vought F6U Pirate|F6U Pirate]], and [[Vought F7U Cutlass|F7U Cutlass]]. The Navy initially planned on having each missile be operational in a sequential order, starting with the simple Regulus and ending with the more complex but capable Triton in 1960. However, both the Rigel and Triton were powered by [[Ramjet|ramjets]], which presented a significant challenge as the technology was too immature for immediate use, eventually leading to both programs' cancellation.<ref name=":0" /><ref name=":2">{{Cite book |last=Stumpf |first=David |title=Regulus: The Forgotten Weapon |publisher=[[Turner Publishing Company]] |isbn=978-1563112775 |publication-date=January 1, 1997}}</ref>{{Rp|page=51}}<ref name=":1">{{Cite web |title=The Evolution of the Cruise Missile |url=https://apps.dtic.mil/sti/tr/pdf/ADA162646.pdf |archive-url=http://web.archive.org/web/20250202113644/https://apps.dtic.mil/sti/tr/pdf/ADA162646.pdf |archive-date=2025-02-02 |access-date=2025-03-05 |website=apps.dtic.mil}}</ref>{{Rp|page=114, 117}}

==== Design ====
The contract required the missile to have a range of {{convert|500|nmi|km}} at Mach 0.85, a {{convert|3000|lb|kg|adj=on}} warhead, and a [[circular error probable]] (margin of error) of {{convert|25|nmi|km}}.<ref name=":1" />{{Rp|page=114}} Regulus was designed to be {{convert|30|ft|m}} long, {{convert|10|ft|m}} in wingspan, {{convert|4|ft|m}} in diameter, and would weigh between {{convert|10000|and|12000|lb|kg}}. The missile somewhat resembled the contemporary [[Republic F-84 Thunderjet|F-84 Thunderjet]] fighter aircraft, but without a cockpit, and test versions were equipped with landing gear so that they could be recovered and re-used.<ref name="ReferenceA" /> After launch, Regulus would be guided toward its target by control stations, typically by submarines or surface ships equipped with guidance equipment. It could also be flown remotely by chase aircraft.<ref name="ReferenceA" /> (Later, with the "Trounce" system (Tactical Radar Omnidirectional Underwater Navigational Control Equipment), one submarine could guide it).<ref>Friedman, p. 178</ref> Army-Navy competition complicated both the Matador's and the Regulus' developments. The missiles looked alike and used the same engine. They had nearly identical performances, schedules, and costs. Under pressure to reduce defense spending, the [[United States Department of Defense]] ordered the Navy to determine if Matador could be adapted for their use. The Navy concluded that the Navy's Regulus could perform the Navy mission better.<ref>David K. Stumpf, ''Regulus: America's First Nuclear Submarine Missile'', Turner Publishing Company, 1996. pp 21-22</ref>

Regulus had some advantages over Matador. It required only two guidance stations while Matador required three.<ref>Friedman, p. 263</ref> It could also be launched quicker, as Matador's boosters had to be fitted while the missile was on the launcher while Regulus was stowed with its boosters attached. Finally, Chance Vought built a recoverable version of the missile, designated '''KDU-1''' and also used as a target drone, so that even though a Regulus test vehicle was more expensive to build, Regulus was cheaper to use over a series of tests. The Navy program continued, and the first Regulus flew in March 1951.

Due to its size and regulations concerning [[oversize load]]s on highways, Chance Vought collaborated with a firm that specialized in trucking oversize loads to develop a special tractor trailer combination which could move a Regulus I missile.<ref>[https://books.google.com/books?id=1t4DAAAAMBAJ&dq=1954+Popular+Mechanics+January&pg=PA128 Build Special Trailer To Move Bulky Missile."] ''Popular Mechanics'', June 1954, p. 128.</ref>

===Ships and submarines deployed with Regulus I===
{{Main|Regulus missile submarines}}[[File:USS Tunny (SSG-282) Regulus launching sequence c1956.jpg|thumb|{{USS|Tunny|SS-282|6}} launches a Regulus I in 1956.]]
The first launch from a submarine occurred in July 1953 from the deck of {{USS|Tunny|SSG-282|6}}, a [[World War II]] fleet boat modified to carry Regulus. ''Tunny'' and her sister boat {{USS|Barbero|SSG-317|6}} were the United States's first nuclear [[Deterrence theory|deterrent]] patrol submarines. They were joined in 1958 by two purpose-built Regulus submarines, {{USS|Grayback|SSG-574|6}}<ref>Stumpf, pp 134</ref> and {{USS|Growler|SSG-577|6}},<ref>Stumpf, pp 142</ref> and, later, by the nuclear-powered {{USS|Halibut|SSGN-587|6}}.<ref>Stumpf, pp 151</ref> ''Halibut'', with its extremely large internal hangar could carry five missiles and was intended to be the prototype of a whole new class of cruise missile firing SSG-N submarines.<ref>''Regulus: The First Nuclear Missile Submarines'' documentary, Spark, 2002.</ref>

The Navy strategy called for four Regulus missiles to be at sea at any given time. Thus, ''Barbero'' and ''Tunny'', each of which carried two Regulus missiles, patrolled simultaneously. ''Growler'' and ''Grayback'', with four missiles each, or ''Halibut'', with five, could patrol alone. Operating from [[Pearl Harbor]], Hawaii, the five Regulus submarines made 40 nuclear deterrent patrols in the Northern Pacific Ocean between October 1959 and July 1964, including during the [[Cuban Missile Crisis]] of 1962. According to the documentary "Regulus: The First Nuclear Missile Submarines" by [[Nick T. Spark]], their primary task in the event of a nuclear exchange would be to eliminate the Soviet naval base at [[Petropavlovsk-Kamchatsky]]. These deterrent patrols represented the first ever in the history of the submarine Navy and preceded those made by the [[Polaris missile]] firing submarines.<ref name="ReferenceA"/>

{| class="wikitable" style="margin: 1em auto;"
!colspan=9|Regulus submarines
|-
!Class
!Name
!In Commission
!Number of<br/> missiles
!Post-Regulus use
|-
|[[Gato-class submarine|''Gato'']]
|{{USS|Tunny|SS-282|2}}
|1953-1965
|rowspan=2|2
|Converted to amphibious transport submarine
|-
|[[Balao-class submarine|''Balao'']]
|{{USS|Barbero|SS-317|2}}
|1955-1964
|Expended as target 1964
|-
|rowspan=2|[[Grayback-class submarine|''Grayback'']]
|{{USS|Grayback|SSG-574|2}}
|1958-1964
|rowspan=2|4
|Converted to amphibious transport submarine
|-
|{{USS|Growler|SSG-577|2}}
|1958-1964
|Decommissioned, memorial 1988
|-
|[[Halibut-class submarine|''Halibut'']]
|{{USS|Halibut|SSGN-587|2}}
|1960-1964
|5
|Converted to special mission submarine
|}
The Regulus firing submarines were relieved by the {{sclass|George Washington|submarine|1}}s carrying the [[Polaris missile]] system.<ref>Friedman, pp. 177-191</ref> ''Barbero'' also earned the distinction of launching the only delivery of [[missile mail]].

Additional submarines including USS ''Cusk'' and USS ''Carbonero'' were equipped with control systems that allowed them to take control of a Regulus in flight, thus extending its range in a tactical situation.<ref name="ReferenceA"/>

Regulus was also deployed by the U.S. Navy in 1955 in the Pacific on board the cruiser {{USS|Los Angeles|CA-135|6}}. In 1956, three more followed: {{USS|Macon|CA-132|6}}, {{USS|Toledo|CA-133|6}}, and {{USS|Helena|CA-75|6}}. These four {{sclass|Baltimore|cruiser|1}}s each carried three Regulus missiles on operational patrols in the Western Pacific. ''Macon''{{'s}} last Regulus patrol was in 1958, ''Toledo''{{'s}} in 1959, ''Helena''{{'s}} in 1960, and ''Los Angeles''{{'s}} in 1961.

[[File:USS Los Angeles (CA-135) firing a Regulus I missile on 7 August 1957 (NH 97391).jpg|thumb|right|A Regulus I fired from {{USS|Los Angeles|CA-135|6}}, 1957.]]Ten aircraft carriers were configured to operate Regulus missiles (though only six ever launched one). {{USS|Princeton|CV-37|6}} did not deploy with the missile but conducted the first launch of a Regulus from a warship. {{USS|Saratoga|CVA-60|6}} also did not deploy but was involved in two demonstration launches. {{USS|Franklin D. Roosevelt|CVA-42|6}} and {{USS|Lexington|CV-16|6}} each conducted one test launch. {{USS|Randolph|CV-15|6}} deployed to the Mediterranean carrying three Regulus missiles. {{USS|Hancock|CV-19|6}} deployed once to the Western Pacific with four missiles in 1955. ''Lexington'', ''Hancock'', {{USS|Shangri-La|CV-38|6}}, and {{USS|Ticonderoga|CV-14|6}} were involved in the development of the Regulus Assault Mission (RAM) concept. RAM converted the Regulus cruise missiles into an [[unmanned aerial vehicle]] (UAV): Regulus missiles would be launched from cruisers or submarines, and once in flight, guided to their targets by carrier-based pilots with remote control equipment.

===Replacement and legacy===
Despite being the U.S. Navy's first underwater nuclear capability, the Regulus missile system had significant operational drawbacks. In order to launch, the submarine had to surface and assemble the missile in whatever sea conditions it was in. Because it required active radar guidance, which only had a range of {{cvt|225|nmi|mi km|abbr=on}}, the ship had to stay stationary on the surface to guide it to the target while effectively broadcasting its location. This guidance method was susceptible to jamming and since the missile was subsonic, the launch platform remained exposed and vulnerable to attack during its flight duration; destroying the ship would effectively disable the missile in flight.<ref name="DS">[http://www.designation-systems.net/dusrm/m-6.html Vought SSM-N-8/RGM-6 Regulus]. ''Designation-Systems.net''.</ref><ref>{{cite web |url=http://blog.nuclearsecrecy.com/2018/05/10/a-view-from-the-deep/|title=A View from the Deep|last1=Wellerstein|first1=Alex|author-link1=Alex Wellerstein|date=10 May 2018|website=The Nuclear Secrecy Blog|access-date=15 June 2019}}</ref>

Production of Regulus was phased out in January 1959 with delivery of the 514th missile; in 1962, it was redesignated RGM-6.<ref name="DS"/> It was removed from service in August 1964. Some of the obsolete missiles were expended as targets at [[Eglin Air Force Base]], Florida. Regulus not only provided the first nuclear strategic deterrence force for the [[United States Navy]] during the first years of the [[Cold War]] and especially during the [[Cuban Missile Crisis]], preceding the [[UGM-27 Polaris|Polaris missile]]s, [[UGM-73 Poseidon|Poseidon missile]]s, and [[Trident (missile)|Trident missile]]s that followed, but it was also the forerunner of the [[Tomahawk (missile family)|Tomahawk cruise missile]].[[File:Vought KDU-1 Regulus in flight.jpg|thumb|A KDU-1 target drone]]Following retirement, a number of Regulus I missiles were converted for [[target drone]] usage under the designation BQM-6C.<ref name="DS"/>

==Regulus II==
{{Main|SSM-N-9 Regulus II}}
A second generation supersonic [[Vought]] [[SSM-N-9 Regulus II]] cruise missile with a range of {{Convert|1,200|NM|km}} and a speed of Mach 2 was developed and successfully tested, including a test launch from ''Grayback'', but the program was canceled in favor of the [[UGM-27 Polaris]] nuclear ballistic missile.<ref name="ReferenceA"/>

The Regulus II missile was a completely new design with improved guidance and double the range, and was intended to replace the Regulus I missile. Regulus II-equipped submarines and ships would have been fitted with the [[Inertial navigation system|Ships Inertial Navigation System]] (SINS), allowing the missiles to be aligned accurately before take-off.

Forty-eight test flights of Regulus II prototypes were carried out, 30 of which were successful, 14 partially successful and four failures. A production contract was signed in January 1958 and the only submarine launch was carried out from ''Grayback'' in September 1958.

Due to the high cost of the Regulus II (approximately one million dollars each), budgetary pressure, and the emergence of the [[UGM-27 Polaris]] SLBM (submarine-launched ballistic missile), the Regulus II program was canceled on 18 December 1958. At the time of cancellation Vought had completed 20 Regulus II missiles with 27 more on the production line. Production of Regulus I missiles continued until January 1959 with delivery of the 514th missile, and it was withdrawn from service in August 1964.

Both Regulus I and Regulus II were used as target drones after 1964.<ref name="ReferenceA"/>

== Surviving examples ==
[[File:Misil regulus.JPG|thumb|Regulus I in launch position on {{USS|Growler|SSG-577|6}}.]]

The following museums in the United States have Regulus missiles on display as part of their collections:
;[[Carolinas Aviation Museum]], Charlotte, North Carolina
:Regulus I missile in launch position at the [[Carolinas Aviation Museum]] in Charlotte, North Carolina. It is mounted on a catapult launching stand used for aircraft carrier launches and was restored late 2006 after having been on outdoor display for a number of years.
;[[Frontiers of Flight Museum]], [[Dallas Love Field]], Texas
:Regulus II missile
;[[Intrepid Sea-Air-Space Museum]], New York City, New York
:Regulus I cruise missile can be seen ready for simulated launch on board {{USS|Growler|SSG-577|6}} at the [[Intrepid Sea-Air-Space Museum]] in New York City.
;Point Mugu Missile Park, [[Naval Air Station Point Mugu]], California
:The museum's collection includes both a Regulus and a Regulus II missile
;{{USS|Bowfin}} Museum, Pearl Harbor, Hawaii
:
;Veterans Memorial Museum, Huntsville, Alabama
:Regulus II missile
;[[Smithsonian Institution]], [[National Air and Space Museum]]
:Regulus I on display at [[Steven F. Udvar-Hazy Center]]
;[[New Jersey Naval Museum]], Hackensack, New Jersey
:Regulus with intact engine
;US Navy [[Pacific Missile Range Facility]], Barking Sands, island of Kauai, Hawaii
:Regulus I restored in 2011 on static display inside the North Gate

==Operators==
*{{USA}}
:[[United States Navy]] (from 1955 to 1964)

==See also==
*[[List of missiles]]
*[[SSBN Deterrent Patrol insignia]]

==References==
{{Reflist}}
{{Refbegin}}
* {{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]] |isbn=1-55750-260-9}}
{{Refend}}

==External links==
{{Commons|SSM-N-8 Regulus}}
*[http://hometown.aol.com/Reallycoolpix/USSHalibut.html USS Halibut Webpage]
*[http://www.regulus-missile.com US Navy Photos & Documentary film] produced by [[Nick T. Spark]], '' "Regulus: The First Nuclear Missile Submarines" '' which aired initially on the [[History (U.S. TV channel)#Europe|History Channel]] in Europe.
*[https://web.archive.org/web/20080103223620/http://www.carolinasaviation.org/collections/missiles/regulus.html Carolinas Aviation Museum]
*[https://www.amazon.com/Regulus-First-Nuclear-Missile-Submarines/dp/B074TTHNP8/ref=sr_1_1?s=movies-tv&ie=UTF8&qid=1505946662&sr=1-1&keywords=regulus] "Regulus: The First Nuclear Missile Submarines"

{{Vought aircraft}}
{{USN drones}}
{{USN missiles}}
{{US missiles}}
{{Authority control}}

{{DEFAULTSORT:Ssm-N-8 Regulus}}
[[Category:Nuclear cruise missiles of the United States]]
[[Category:Nuclear cruise missiles of the United States Navy]]
[[Category:Cruise missiles of the Cold War]]
[[Category:Cold War nuclear missiles of the United States]]
[[Category:Vought]]
[[Category:Military equipment introduced in the 1950s]]