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Regulus 2
Regulus 2
Regulus 2
Credit: via Andreas Parsch
American supersonic sub-to-surface intermediate-range cruise missile, development started in 1953. Program cancelled in 1958 in deference to Polaris project.

AKA: KD2U-1; RGM-15; SSM-N-9; W27. Status: Cancelled 1958. Payload: 910 kg (2,000 lb). Thrust: 510.90 kN (114,855 lbf). Gross mass: 10,200 kg (22,400 lb). Height: 17.38 m (57.02 ft). Diameter: 1.83 m (6.00 ft). Span: 6.10 m (20.00 ft). Apogee: 18 km (11 mi).

In June 1953 Vought was selected by the US Navy to develop the Regulus II, a supersonic successor to the subsonic Regulus ship-launched cruise missile. The Regulus II would remedy the first generation missile's drawbacks by having autonomous inertial navigation, longer range, and supersonic dash capability through air defenses. However this also resulted in a larger missile, meaning fewer Regulus II's could be deployed per submarine. First test flight was in May 1956, but the schedule slipped due to delays in development of the J79 engine that was to propel the production version. First test launch of the missile from a submarine using the J79 engine was in September 1958. By then the Polaris submarine-launched ballistic missile program was in full development, making cruise missiles obsolete. Regulus was cancelled at the end of 1958, although surplus missiles were flown in guidance technology tests and as targets.

Development Cost $: 144.400 million in 1957 dollars. Maximum range: 1,610 km (1,000 mi). Number Standard Warheads: 1. Standard warhead: W27. Warhead yield: 1,500 KT. Boost Propulsion: Solid rocket. Maximum speed: 2,260 kph (1,400 mph). Initial Operational Capability: 1959.

Historical Essay © Andreas Parsch

Vought SSM-N-9-RGM-15 Regulus II

In June 1953 Vought received a contract to develop a supersonic successor to the SSM-N-8-RGM-6 Regulus cruise missile. The new missile was named Regulus II (although it was a completely new missile, and not a development of Regulus) and received the designation SSM-N-9. The SSM-N-9 designator had been previously assigned temporarily to the MGM-18 Lacrosse missile, before the latter was transferred to the Army as SSM-G-12.

The XRSSM-N-9 Regulus II prototypes had a retractable landing gear for missile recovery, and an interim Wright J65-W-6 engine, which didn't allow flight at the design speed of Mach 2. The first flight of an XRSSM-N-9 occurred in May 1956, and the testing of this model continued until the end of 1957. In 1958 testing continued with the improved XRSSM-N-9a prototypes, which still had the landing gear, but were equipped with the General Electric J79-GE-3 engine intended for the tactical missiles. The first launch of a Regulus II from a submarine occurred in September 1958. The designations YTSSM-N-9a and TSSM-N-9a were reserved for evaluation and production models of the landing gear equipped Regulus II, to be used for training purposes.

Regulus II was a Mach 2 cruise missile design, which could also attain a significantly higher altitude and range than the SSM-N-8 Regulus I. The radio command guidance of the Regulus I was dropped in favour of an inertial guidance system, making the SSM-N-9 much less prone to electronic jamming. Despite these advantages, the Regulus II would have been hopelessly obsolete with the advent of the UGM-27 Polaris SLBM (Submarine-Launched Ballistic Missile), and therefore the tactical SSM-N-9 Regulus II cruise missile was cancelled in late 1958. Nevertheless the evaluation of the missile's performance continued, and the first XSSM-N-9 tactical prototype (substituting the landing gear for additional fuel, allowing full range and Mach 2 capability) was launched in November 1959, followed by YSSM-N-9 evaluation models. Interestingly, the SSM-N-9 was redesignated as RGM-15A in June 1963, more than 4 years after the program had been cancelled.

In the final stages of the Regulus II program, around 1958, it was apparently proposed to equip the missile with a radar map matching guidance system. In this system, which is generally known as TERCOM (Terrain Contour Matching), the radar map of the terrain below the missile's flight path is constantly matched with preloaded radar maps, allowing the missile to follow a precise preprogrammed path. For evaluation missiles equipped with this guidance system, the designations YTSSM-N-9b and YSSM-N-9a were allocated to improved YTSSM-N-9a and YSSM-N-9, respectively. However, none of these variants were built.

After program cancellation, the remaining flight test missiles were used as KD2U-1 supersonic target drones by the U.S. Navy and the U.S. Air Force. The latter used the KD2U-1 extensively during testing of the IM-99-CIM-10 Bomarc surface-to-air missile. In June 1963, the KD2U-1 was redesignated as MQM-15A. Late in their career, some runway-launched MQM-15A drones were redesignated as GQM-15A.

Only 54 Regulus II test missiles were built before production was cancelled.


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for XRSSM-N-9 and XSSM-N-9 (RGM-15A):

  XRSSM-N-9 XSSM-N-9 (RGM-15A)
Length (w-o pitot tube) 17.52 m (57 ft 6 in); incl. pitot tube: 19.53 m (64 ft 1 in)
Diameter 1.27 m (50 in)
Wingspan 6.12 m (20 ft 1 in)
Weight (w-o booster) 10400 kg (23000 lb); booster: 3170 kg (7000 lb)
Speed Mach 1.8 Mach 2
Ceiling 14300 m (47000 ft) 18000 m (59000 ft)
Range 550 km (300 nm) 1850 km (1000 nm)
Propulsion Cruise: Wright J65-W-6 turbojet; 65 kN (14600 lb)
Booster: Aerojet General solid-fueled rocket; 511 kN (115000 lb)
Cruise: General Electric J79-GE-3 turbojet; 69 kN (15600 lb)
Booster: Rocketdyne solid-fueled rocket; 600 kN (135000 lb)
Warhead none W-27 thermonuclear (2 MT)
Main Sources

[1] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[2] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[3] James N. Gibson: "Nuclear Weapons of the United States", Schiffer Publishing Ltd, 1996
[4] Vought Heritage Museum Website
[5] BuAer Instruction 05030.4A: "Model Designation of Naval Aircraft, KD Targets, and BuAer Guided Missiles", Dept. of the Navy, 1958

Family: IRCM, submarine-launched, US Cruise Missiles. Country: USA. Agency: Vought. Bibliography: 563.

Photo Gallery

Regulus 2Regulus 2
Credit: via Andreas Parsch

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