Anti-Aircraft Weapons

Anti-Aircraft Weapons, ordnance and missiles used defensively to destroy approaching enemy aircraft and missiles.

Before World War II, anti-aircraft weapons consisted of standard infantry rapid-fire automatic rifles and .30-calibre and .50-calibre machine-guns on mountings designed specially to direct fire against air targets. During World War II special 20-mm, 37-mm, 40-mm, 90-mm, 3-in., and 5-in. anti-aircraft guns were developed for use against high-flying aircraft. Anti-aircraft fire was extremely effective because of the invention during World War II of the proximity fuse, a tiny radar set located in the nose of a shell that detonated the charge when the explosion of the shell could be expected to be most effective against the target. In order to increase firepower, the United States Navy mounted two 20-mm anti-aircraft guns, then two 5-in. guns, and later two 40-mm guns and four 40-mm guns on single carriages for simultaneous aiming and firing of all guns on the mount. The US Army used four .50-calibre machine-guns on a single carriage, thereby quadrupling the fire output. “Quad 50s” and “twin 40s” were commonly used against both air and ground targets during the Korean and Vietnam wars.

Anti-aircraft gunners in World War II aimed at sight. In order to increase the accuracy of fire, automatic aiming and range-finding systems were developed, culminating after the war in radar-directed systems that aimed and fired the guns automatically. By the 1960s these fire-direction systems had evolved into computer-controlled systems that could digest a great volume of information quickly and could automatically set in motion the appropriate countermeasures.

The development of rocket-propelled missiles after World War II introduced an entirely new dimension in anti-aircraft defence. A great many surface-to-air missiles were developed that were capable of intercepting aircraft and ballistic missiles approaching their targets at supersonic speeds. Defending missiles were guided by infrared homing devices attracted by the heat given off by the targets, or by radar receivers in the missile that guided it electronically.

The US Army began developing anti-aircraft missiles in 1945. The first missile deployed was the Nike Ajax in 1953, followed shortly by the Nike Hercules; both were designed to provide long-range defence against enemy aircraft and missiles. Later, the Hawk missile was developed to provide shorter-range, tactical air defence. A successor to the Nike Hercules and Hawk systems, the Patriot missile is a mobile, medium- to long-range air defence weapon. Patriot missiles based in Israel and Saudi Arabia intercepted Scud missiles launched from Iraq during the Gulf War.

For close-in air defence, automatic weapons and short-range missiles have been developed. The US Army uses the 20-mm Vulcan automatic gun in conjunction with Chaparrals—heat-seeking missiles—for short-range air defence. In the 1970s the United States and the Soviet Union developed missiles for use against supersonic aircraft; the US Army's Redeye was a heat-seeking missile that could be launched by one person. In the 1980s the Redeye was replaced by the Stinger missile. The versatile British Rapier air defence system can deliver an armour-piercing missile at a distance of 6.4 km (4 mi) at a speed greater than Mach 2. It provided highly effective air defence during the Falklands War.