The Standard Missile was originally developed to replace some of the USN's first SAMs, the Terrier and Tartar missiles of the 1950s. From the time it entered service in the late 60s, it was a success, with upgrades giving it more and more capability throughout the 70s and 80s. It was chosen as the primary weapon for Aegis, as well as arming older ships originally built for Terrier or Tartar. Variants were also produced, most notably an anti-radiation missile for use over Vietnam that also gave the USN an interim anti-ship missile capability in the 1970s.

An SM-2MR with a Fritz-X in the background
By the late 1980s, it was becoming increasingly obvious that the Aegis/Standard team would be incredibly effective against high-altitude targets, but less so against sea-skimming weapons. As a result, another version of the SM-2 was built, known as Block III and designed as RIM-66K/L/M (SM-2MR NTU/Aegis Mk 26/Aegis Mk 41) and RIM-67D (SM-2ER NTU). This version had improvements to the seeker and guidance sections to better pick targets out of sea clutter, as well as an improved proximity fuze. It was followed in 1991 by Block IIIA, which introduced an improved warhead and more fuze upgrades, but didn't change the designations. The end of the Cold War saw the NTU ships retired, mostly in the mid-to-late 90s, and the Mk 26 Ticonderogas axed shortly thereafter. This entirely killed off the RIM-67, and saw the RIM-66M as the only survivor of its branch, making things much easier to keep track of. It was the only version to get the Block IIIB upgrade, which saw an IR seeker added to give improved performance in an ECM-heavy environment, as well as probably some limited capability over the horizon, particularly against surface targets. Technically, both Block IIIA and Block IIIB remain the current versions, although there have been a number of upgrades over the years, including another new fuze and software changes to improve maneuverability. I suspect the version numbers have stayed the same as part of a designation engineering strategy. Read more...








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