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 submarines and the , which were designed for the missile, and possibly eventually on four heavy cruisers 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 systems 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 Support for the program was finally withdrawn on 18 December 1958, when Secretary of the Navy Thomas S. Gates cancelled the project.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