ABSTRACT
The Sidewinder antiaircraft missile is one of the more spinechilling products of 20th-century engineering. It pursues its prey with a purposiveness and “intelligence” that would fascinate a Renaissance clockmaker. If the prey attempts to avoid the oncoming missile, the missile alters its course so as to nullify the evasive maneuvers of its prey. The basic principles underlying the design of this lethally purposive machine are the same principles that direct the movement of its biological namesake, the sidewinder rattlesnake, which preys upon small warmblooded animals in the deserts of the southwestern United States. The missile, like the snake, is steered by heat sensitive receptors. The missile has its infrared receptors in an array all around the nose; the snake has his in the pits beneath his eyes. Jet planes are excellent sources of infrared radiation; so are warm-blooded animals in the cold desert night (Bullock & Diecke, 1956; Dullemeijer, 1961; Noble & Schmidt, 1937; Shin-schi & Goris, 1974). The mechanism which keeps the missile oriented toward the hot rear-end of a jet plane is a servomechanism. The mechanism that keeps a snake oriented toward its intended prey is probably also a servomechanism, but we know more about the missile's machinery, so we will use the missile to explicate the concept of a servomechanism.
