The Phalanx anti-missile system is being replaced by SeaRAM. What's interesting about this is that SeaRAM is basically the Phalanx system, with the 20mm gun replaced with a box of eleven RAM (RIM-116 "Rolling Air Frame") missiles. The Phalanx was developed in the 1970s, and entered service in 1977. RAM was developed in the 1980s, and didn't enter service until 1993. RAM has a longer range (7.5 kilometers) than the Phalanx (two kilometers) and was originally designed to be aimed using the ships fire control systems. Phalanx, on the other hand, has its own radar and fire control system and, once turned on, will automatically fire at any incoming missiles. This was necessary, as some anti-ship missiles travel at over a 500 meters a second. With SeaRAM, you've got a little more time, and can knock down the incoming missile farther from the ship. This is important, because it was feared that a large, very fast anti-ship missile (which the Russians prefer, and sell to foreigners), even when shot up by Phalanx, might still end up having parts of it slam into the target ship. Since SeaRAM has eleven missiles ready to fire, it can also engage several targets at once, something the Phalanx could not do.
The RAM missiles are 127mm in diameter, 9.3 feet long and weigh 162 pounds each. The terminal guidance system is heat seeking. Basically, it uses the rocket motor and warhead from the Sidewinder air-to-air missile, and the guidance system from the Stinger shoulder fired anti-aircraft missile. SeaRAM missiles cost about $450,000 each.
SeaRAM is meant to provide combat support ships that normally have no defenses, or at least no combat radars and fire control system. The new LCS will use the SeaRAM as well.