The second generation of Standard missile, the Standard Missile 2, was developed for the Aegis combat system, and New Threat Upgrade program that was planned for existing Terrier and Tartar ships.
The destroyer USS Mahan 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 for each phase of the missile's flight except the terminal phase where semi-active homing was retained.
This design change was made so that missiles could time share illumination radars and enable equipped ships to defend against saturation missile attacks.

Terrier ships reequipped as part of the New Threat Upgrade were refit to operate the RIM-67B (SM-2ER Block II) missile.
However, Aegis ships were not equipped with launchers that had space enough for the longer RIM-67B.
The RIM-156A Standard SM-2ER Block IV with the Mk 72 booster was developed to compensate for the lack of a long range SAM for the Ticonderoga class of Aegis cruisers.
The Mk72 booster allows the RIM-156A to fit into the Mk41 guided missile launch system.
This configuration can 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The USN rescinded the requirement for the nuclear armed missile in the 1980s, and the project was canceled.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 Standard Missile 6 ERAM is a new generation of Standard extended range missiles, which became operational in 2013.
The second generation of Standard missile, the Standard Missile 2, was developed for the Aegis combat system, and New Threat Upgrade program that was planned for existing Terrier and Tartar ships. The destroyer USS Mahan 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 for each phase of the missile's flight except the terminal phase where semi-active homing was retained. This design change was made so that missiles could time share illumination radars and enable equipped ships to defend against saturation missile attacks.
Terrier ships reequipped as part of the New Threat Upgrade were refit to operate the RIM-67B (SM-2ER Block II) missile. However, Aegis ships were not equipped with launchers that had space enough for the longer RIM-67B.
The RIM-156A Standard SM-2ER Block IV with the Mk 72 booster was developed to compensate for the lack of a long range SAM for the Ticonderoga class of Aegis cruisers. The Mk72 booster allows the RIM-156A to fit into the Mk41 guided missile launch system. This configuration can 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 Standard Missile 6 ERAM is a new generation of Standard extended range missiles, which became operational in 2013.
RIM-67 Standard