RIM-174 Standard SM-6
A new missile being developed by the U.S. Navy, the RIM-174A Standard SM-6, complements the SM-3 missile, which is only capable against ballistic missiles and satellites. The SM-6 is an over-the-horizon-capable surface-to-air missile, with greater range than the RIM-156A SM-2 Block IV missile
In the new missile, active radar seeker of the AIM-120C-7 AMRAAM air-to-air missile has been added for terminal guidance. Because of that seeker, the ERAM acronym, in 2008, was redefined to mean Extended Range Active Missile. The active terminal radar replaces the semi-active radar homing of the RIM-156, which now requires the AN/SPG-62 illuminator, which is not over-the-horizon-capable.
The additional range will allow naval vessels to conduct anti-air warfare both over the sea and over the land. By using existing components, development risk is low, with operational capacity expected in fiscal year 2010. It extends the existing layered U.S. anti-air warfare system, the RIM-156 Standard SM-2 is the long-range weapon, with one per VLS cell, which can engage targets at least 130 nm/240 km away.
ESSM, with a range of 27+ nm/50+ km, forms the next band. For final defense, there is the 9 km (5 nm) RIM-116 Rolling Airframe Missile. U.S. forces on land will have additional final counter-rocket, artillery and mortar (C-RAM) capability, currently experimental with the Phalanx close-in weapons system.