Projects

Variations in the speed, position, and launch direction of the missile at thrust cutoff will produce errors at the impact point . These errors are of two types-errors in the intended plane which cause either a long or a short hit, and out-of-plane errors which cause the missile to hit to the right or left of the target. For brevity , we will refer to errors in the intended plane as "down-range " errors, and out-of-plane errors as "cross-range " errors. There are two possible sources of cross-range error and these will be treated first. 6 .3 . 1 Effect of a Lateral Displacement of the Burnout Point. If the thrust cutoff point is displaced by an amount, .6X, perpendicular to the intended plane of the trajectory and all other conditions are nominal,the cross-range error, .6C, at impact can be determined from spherical trigonometry . In Figure 6 . 3 - 1 we show the ground traces of the intended and actual trajectories. F or purposes of this example , suppose the intended burnout point is on the equator and the launch azimuth is due north along a meridian toward the intended target at A. The actual burnout point occurs at a point on the equator a distance , .6X to the east but with the correct launch azimuth of due north. As a result the missile flies up the wrong meridian , impacting at B. The arc length .6C represents the cross-range error. It is customary in spherical trigonometry to measure arc length in terms of the angle subtended at the center of the sphere so that b oth .6X and .6C