Fundamentals of proportional navigation

Proportional navigation has proved to be a useful guidance technique in several surface-to-air and air-to-air missile systems for interception of airborne targets. In this article, which is tutorial in nature, the basic theory of proportional navigation is presented and clarified. In addition, two variations on this guidance method are treated: one in which the commanded acceleration is biased by a small value of the measured rotational rate of the line of sight between the interceptor and its target, and one in which the line-of-sight rotational rate is reduced to a prescribed value (dead space) and then maintained at this rate until intercept. The analysis is directed, by example, to the case of the exoatmospheric interception of a satellite; however, the guidance theory presented is also applicable to the intercept of a nonmaneuvering airborne target.