Editing SSM-N-8 Regulus (section)

==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 Production of Regulus I missiles continued until January 1959 with delivery of the 514th missile, and it was withdrawn from service in August 1964.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"/>