A steering law satisfying the constant total time of flight constraint.

Abstract

The problem considered in this paper is that of steering a rocket vehicle so as to achieve a ballistic trajectory that arrives at a specified position at a specified time. An exoatmospheric steering equation, which is only a function of the current state of the booster, is derived from the dynamic equation of velocity-to-be-gained, and its accuracy is shown to be relatively insensitive to variations in booster characteristics and to the coordinate system with respect to which steering is done. Moreover, steering can easily be done so as to satisfy such additional constraints and boundary conditions as near optimality with respect to fuel consumption for nonthrottleable, continuous-burn engines, low turning rates, and a roll-axis attitude constraint at thrust termination. Simulation results show that since the steering equation is sufficiently accurate, no trajectory-de pendent preflight calculations need be done when a simple in-flight choice of certain constants is made.