Optimal biased proportional navigation

Proportional navigation has frequently been used for the guidance of interceptor missiles. When such missiles are operated outside the atmosphere, since a velocity change can be accomplished only by the expenditure of propellant, it is important that any path correction be achieved efficiently. In this correspondence, it is shown that the addition of an appropriate bias term to a proportional navigation guidance equation allows an interceptor missile to attain an efficiency which can be made to approach that of an optimum system.