Russia is continuing to replace its Cold War era S-300 air defense systems with the newer S-400 (SA-21). In the last six years 12 S-400 battalions have entered service. Each consists of 4-8 launcher vehicles (each with two missiles, plus two reloads) plus radar vehicles and a command vehicle. Russia is planning to have 56 S-400 battalions in service by the end of the decade. Despite this, in 2012 the Defense Ministry ordered more of the older S-300V (SA-12) system. This seems to indicate that the S-400 is having problems (it has certainly encountered many delays so far). The S-500, while still in development, has also had several embarrassing delays announced.
The original S-300 was known to NATO, during the Cold War, as the SA-10. This system entered service in the late 1970s and was upgraded several times since then. One major upgrade came to be called the SA-12 and it entered service in the late 1980s. Finally, there was the SA-21, which was so different from the original S-300 that it was given a new name by the Russians: the S-400. These systems began entering service, slowly, in 2007.
By 2012 Russia had deployed S-400 battalions near Kaliningrad, Moscow and the Far East. Russia has 160 older S-300 battalions, most of them the SA-10 model. A third of the existing S-300 battalions are not in service (and are supposed to be in storage, just in case). Each S-300 battalion had a long-range search radar to detect targets and six launcher vehicles (each carrying four or two missiles). Each of the new S-400 battalion has eight launchers, each with two missiles plus a control center and radar.
The S-300V/SA-12 missiles had a range of 75 kilometers and were considered somewhat similar to the American Patriot systems. Later models of the S-300V had some capability to shoot down short range ballistic missiles. The SA-12 missiles were carried in canisters (either four or two per launcher vehicle). Each launcher vehicle also contained a guidance radar.
The S-400 claims to be superior to the U.S. Patriot and is expensive. Russia is now offering to export the S-400, despite all the advanced technology in it. The S-400 missiles weigh 1.8 tons each, are 8.4 meters (26 feet) long, and about 50cm (20 inches) in diameter. There are actually three different missiles, each with a different range (120, 250 and 400 kilometers). All missiles can reach targets as high as 30 kilometers (93,000 feet). The missile has a 145.5 kg (320 pound) warhead. The target acquisition radar has a range of 700 kilometers. S-400 missiles can hit short range ballistic missiles up to 60 kilometers away.
The S-400 has more range than the U.S. Patriot (max 160 kilometers), weighs twice as much, and claims the ability to detect stealthy aircraft. The S-400 also has an anti-missile capability, which is limited to shorter range (under 3,500 kilometers) ballistic missiles. That would mean a warhead coming in at about 5,000 meters a second (the longer the range of a ballistic missile, the higher its re-entry speed).
The S-400 system actually has two types of missiles, one of them being smaller with a shorter range (120 kilometers) and two larger missiles with much more range (250 and 400 kilometers). The 120 kilometers range missile are deployed four to a launcher, like S-300 systems. The S-400 has no combat experience but U.S. intelligence believes that the tests these systems have undergone indicate it is a capable air defense weapon. Just how capable won't be known until it actually gets used in combat. None of the S-300 series systems have any combat experience either but some models have performed well in tests.