Re-Entry Guidance and Flight Path Control

The capabilities and limitations of a specific flight path control law for range maneuvering during the atmospheric phase of re-entry from orbit, as determined by a digital computer study, are presented. Results of this study demonstrate that a relatively simple guidance and flight path control loop, utilizing a preprogrammed normalized trajectory plus vehicle velocity and range-to-go measurements, is very effective; range dispersions of more than ?? 100 nautical miles, caused by initial conditions or to uncertainties in lift-to-drag ratio, are reduced to less than one nautical mile. Variations in terminal accuracy are evolved as functions of control law gain, velocity measurement errors (via inertial guidance or ground radar tracking) and severe head winds.