SSM - N - 9 Regulus II The SSM - N - 9 Regulus II cruise missile was a supersonic guided missile armed with a nuclear warhead , intended for launching from surface ships and submarines of the U . S . Navy ( USN ) . History . The limitations of the Regulus I were well known by the time it entered service in 1955 , so the Navy issued a specification for a surface - launched supersonic shipborne cruise missile , equipped to carry a nuclear warhead , that had greater range , accuracy and resistance to countermeasures . Development of the Regulus II was well under way when the program was canceled in favor of the UGM - 27 Polaris SLBM ( Submarine - Launched Ballistic Missile ) system , which gave unprecedented accuracy as well as allowing the launch submarine to stay submerged and covert . Prototype and initial production missiles were later converted to Vought KD2U - 1 supersonic target drones for the U . S . Navy and the U . S . Air Force , which used the KD2U - 1 during tests of the Boeing IM - 99 / CIM - 10 Bomarc SAM ( Surface to Air Missile ) . Interestingly , the SSM - N - 9a Regulus II was redesignated as the RGM - 15A in June 1963 , nearly five years after the missile program had been terminated . At the same time the KD2U - 1 target drone was redesignated as the Vought MQM - 15A . Some targets equipped with landing gear were redesignated as Vought GQM - 15As . Design and development . The major drawback of the original Regulus was the use of radio - command guidance , which required a constant radio link with the launch ship / submarine that was relatively easy to interfere with . The earlier missile also suffered from restricted range which required the launch ship to launch the missile close to the target and remain exposed until the missile hit the target . To alleviate these drawbacks , the Regulus II was designed with an inertial navigation system , which required no further input from the launch ship / boat after launch , and a greater range through improved aerodynamics , larger fuel capacity , and a lower specific fuel consumption from its jet engine . Prototype missiles were built , designated XRSSM - N - 9 " Regulus II " , with retractable landing gear , to allow multiple launches , and Wright J65 - W - 6 engines and Aerojet General booster , which restricted them to subsonic flight . The first flight of the XRSSM - N - 9 took place in May 1956 . Beginning in 1958 , testing was carried out with the XRSSM - N - 9a , equipped with the General Electric J79 - GE - 3 turbojet and a Rocketdyne solid - fueled rocket booster to allow the entire flight envelope to be explored . Evaluation and training missiles with retractable undercarriage were produced as the YTSSM - N - 9a and TSSM - N - 9a respectively . After land - based testing , trials including test missile firings were carried out on board the , which had been modified with the replica of a submarine missile hangar and launching system . The SSM - N - 9 Regulus II missile was intended to be launched from the deck of an SSG ( guided missile submarine ) , and the missile most likely would have been deployed on the two Grayback - class submarine s and the , which were designed for the missile , and possibly eventually on four heavy cruiser s that had deployed with Regulus I and 23 other submarines potentially available for conversion . Carrying two Regulus II missiles in a hangar integral with the hull ( more on surface ships ) , submarines and ships equipped with the " Regulus II " would have been equipped with the SINS ( Ship ' s Inertial Navigation System ) , allowing the control system s of the missiles to be aligned accurately before launching . Forty - eight test - flights of Regulus II prototypes were carried out , 30 of which were successful , 14 partially successful and only four failures . A production contract was signed in January 1958 and the only submarine launch was carried out from USS " Grayback " in September 1958 . Due to the high cost of the missiles ( approx one million dollars each ) , budgetary pressure , and the emergence of the SLBM , the Regulus missile program was terminated on 19 November 1958 . Support for the program was finally withdrawn on 18 December 1958 , when Secretary of the Navy Thomas S . Gates canceled the project . At the time of the cancelation , Vought had completed 20 missiles with 27 more on the production line . Description . The airframe followed contemporary aircraft construction techniques , with weight savings from the use of advanced materials and the short airborne life of the missile . The fuselage was essentially tubular , tapering to a point at the nose , housing the guidance equipment , warhead and systems equipment . The engine was fed with air through a distinctive wedge shaped intake under the center fuselage . Its swept wings attached to its fuselage at the middle position , roughly halfway along its length , and a large swept fin attached to the top of the fuselage at the rear which was sometimes augmented by a large ventral fin at the extreme rear of the fuselage . Primary control of the Regulus II was through the use of elevons fitted to the outer half of the wing trailing - edges , as the missile was not fitted with a tailplane , and a rudder fitted to the trailing edge of the fin . Flaps were fitted to the inner half of the trailing edge for use during takeoff . Additional stability and control in pitch was provided by small trapezoidal canard foreplanes near the nose of the fuselage . To launch the missile , the carrier vessel had to surface and deploy the missile and launch apparatus , which consisted of a zero length launcher . Once deployed , the missile had to be linked to the submarine or ships navigation system to align the inertial navigation system and input target co - ordinates . With the navigation system ready and launch authorisation given , the missile engine would be run - up to full power with afterburner and the large solid - fuelled rocket booster ignited , immediately the missile would leave the zero length launcher and continue to the target autonomously . Regulus Target Drones . Suitable missiles from the development program and production line were converted to supersonic target drone s as the KD2U - 1 , later redesignated as the MQM - 15A and GQM - 15A . These targets were used for training of BOMARC surface - to - air missile crews firing from Santa Rosa Island , Florida , and controlled by the Montgomery Air Defense Sector , Gunter Air Force Base , Montgomery , Alabama . The KD2U - 1 targets were launched from the Eglin Gulf Test Range base near Ft . Walton Beach , Florida . Drone flights at Eglin commenced on 3 September 1959 , making 46 flights with 13 missiles . After the BOMARC tests the remaining missiles were moved to Roosevelt Roads Naval Station , in Puerto Rico by 30 September 1961 , where flights were begun to test Tartar , Terrier , and Talos surface - to - air missile s . Upon completion of the testing in Puerto Rico in 1963 , the Regulus II drones were moved to Point Mugu , California , where they remained in use until December 1965 .