The P-150 Malakhit (Malachite, Малахит in Russian) missile, NATO reporting name SS-N-9 Siren, is a medium-range anti-ship missile designed by the Soviet Union in the early 1970s. It was initially designed for the submarine force, but was later adapted for surface launch.
The Malakhit was developed to fill the Soviet Navy's need for a good submarine-launched anti-ship missile. The solutions that existed at the time were unsuitable: The SS-N-2 Styx with its hypergolic fuel was too dangerous, while the massive SS-N-3 Shaddock could be carried only in small numbers and required the sub to stay surfaced and in radar contact to guide it unless another ship was available for handoff. The USSR's solution was to devise a medium-range, smaller jet-powered missile that could be launched with only initial target information, or even just a target bearing. Early versions of the Siren had to be launched while surfaced but later versions could be launched from periscope depth.
The P-150 is boosted from its launch tube by a solid-fueled rocket and then transitions to turbojet-powered cruise, flying at around 100m altitude. It then switches on its active radar seeker to acquire its target and attacks with a steep terminal dive. On contact it detonates a 400kg fragmentation warhead, which is sufficient to disable a frigate or heavily damage anything larger. Early versions were vulnerable to chaff and other distraction measures, though newer missiles have some degree of ECM resistance and target discrimination.
Though designed for submarines, the Siren was later adapted for corvettes and missile boats. The Russian Navy has decommissioned all Siren-equipped subs, but numerous corvettes armed with it remain in service. In the recent Russo-Georgian War of 2008, the Russian corvette Mirazh destroyed a Georgian patrol torpedo boat with two P-150 missiles.