The second generation of Standard missile, the Standard Missile 2, was developed for the
Aegis Combat System, and the
New Threat Upgrade (NTU) program that was planned for existing Terrier and Tartar ships. It is the primary anti-air weapon of the US Navy. The
destroyer served as the test platform for the development of the CG/SM-2 (ER) missile program project. The principal change over the Standard Missile 1 is the introduction of inertial guidance until the terminal phase where semi-active homing takes over. Terrier ships re-equipped as part of the New Threat Upgrade were refit to use the RIM-67B (SM-2ER Block I) missile. The RIM-156A Standard SM-2ER Block IV with the Mk 72 booster was developed to provide a long range SAM for the of Aegis
cruisers. The Mk 72 booster allows the RIM-156A to fit into the
Mark 41 Vertical Launching System. This configuration is also be used for terminal phase ballistic missile defense. There was a plan to build a nuclear armed standard missile mounting a
W81 nuclear warhead as a replacement for the earlier Nuclear Terrier missile (RIM-2D). The USN rescinded the requirement for the nuclear armed missile in the 1980s, and the project was canceled. The Standard can also be used against ships, either at line-of-sight range using its semi-active homing mode, or over the horizon using inertial guidance and terminal infrared homing.
RIM-174 SM-6 ERAM is a new generation of Standard extended range missiles which became operational in 2013 designed to supplement the SM-2. As of April 2025, the Navy is considering phasing out the SM-2 series and replacing them with the
PAC-3 MSE variant of the
MIM-104 Patriot missile system, which can be fired from the same VLS systems but is available in greater numbers, can be produced faster, requires fewer interceptors fired to achieve a kill, and has sufficient maneuverability to engage surface-skimming targets as close as 1km away from the launch vessel (a part of the engagement envelope that the
SM-6, which must first boost to high altitudes and dive on a target, cannot engage in as it requires a greater minimum distance). ==Operational history==