Surface-to-air missile

A surface-to-air missile (SAM), or ground-to-air missile (GTAM), is a missile designed to be launched from the ground to destroy aircraft or other missiles. It is one type of antiaircraft system; in modern armed forces, missiles have replaced most other forms of dedicated antiaircraft weapons, with anti-aircraft guns pushed into specialized roles.

The first serious attempts at SAM development took place during World War II, although no operational systems were introduced. Further development in the 1940s and 1950s led to the first operational systems being introduced by most major forces during the second half of the 1950s. Smaller systems, suitable for close-range work, evolved through the 1960s and 1970s, to modern systems that are man-portable. Shipborne systems followed the evolution of land-based models, starting with long-range weapons and steadily evolving toward smaller designs to provide a layered defence that have pushed gun-based systems into the shortest-range roles.

The American Nike Ajax was the first operational guided missile SAM system, and the Soviet Union's S-75 Dvina was the most-produced SAM. Widely used modern examples include the Patriot and S-300 wide-area systems, SM-6 naval missiles, and short-range man-portable systems like the Stinger and Strela-3.

The first known idea for a guided surface-to-air missile was in 1925, when a beam riding system was proposed whereby a rocket would follow a searchlight beam onto a target. A selenium cell was mounted on the tip of each of the rocket's four tail fins, with the cells facing backwards. When one selenium cell was no longer in the light beam, it would be steered in the opposite direction back into the beam. The first historical mention of a concept and design of a surface-to-air missile in which a drawing was presented, was by inventor Gustav Rasmus in 1931, who proposed a design that would home in on the sound of an aircraft's engines.

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