South Korea is equipping its new class of FFX frigates with U.S. weapons (Phalanx and RAM) for protection against anti-ship missiles. European firms were offering comparable systems at competitive prices. But the U.S. systems were selected because they had more of a track record, having been used for years by U.S. warships, and those of many others as well.
Meanwhile, many other nations are replacing the Phalanx anti-missile system with 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 (which can detect incoming missiles more than ten kilometers away). 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 large 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.
But some navies use Phalanx and RAM, to provide a dual layer of defense. Any missiles that get past RAM, then have to get past Phalanx as well. Phalanx uses 20mm depleted uranium shells, to slice through incoming missiles. Phalanx fires shells at the rate of 75 per second. The Phalanx radar can pick up targets five kilometers away.
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.
The FFXs are 3,200 ton ships and are each armed with a 76mm gun, eight anti-ship missiles, six torpedo tubes, plus two RAM launchers and two Phalanx. The ships are highly automated, requiring a crew of only 95. Top speed is 61 kilometers an hour. Range is 7,000 kilometers. Most of the equipment (including electronics) and weapons will be locally built. South Korea plans to build as many as of twenty of these ships. The first six are all to be in service by 2015. The first ship in the class, the Ulsan, will cost $107 million. South Korea hopes to export the FFX to many navies who want a quality, low cost, warship.