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Developments in the field of automatic guidance and control of rockets

1981; American Institute of Aeronautics and Astronautics; Volume: 4; Issue: 3 Linguagem: Inglês

10.2514/3.19735

1533-3884

Advanced Research in Science and Engineering

Introduction T definitions are that navigation determines the vehicle's state for initial conditions as well as during flight; that selects the maneuvering sequence to get from the instantaneous state to a required state; and that executes the maneuvers called for by guidance. These definitions did not exist in the early development years. Navigation corrections were usually taken care of by flight time deviations, which were included in simple guidance functions. Fixed programs, such as flight-tilt programs and roll programs, to rotate the vehicle into its required flight plane have been considered control functions rather than guidance functions and have been exceptions to these definitions. The development of liquid fuel and oxidizer engines made it necessary to stabilize the rockets and to provide attitude control. This included a pitch tilt program, because these rockets with their low initial acceleration had to be launched in a vertical direction. In order to aim at a target the next requirements were to constrain the rocket to a predetermined flight plane and to provide a well-defined velocity vector at propulsion cutoff of the rocket engine. Related but less sophisticated requirements had existed for ship and airplane control. Inertial sensors, such as gimbal suspended gyroscopes and rate gyros, had been used for these systems. In 1912 Prof. Max Schuler had designed a threegyro, three-degree-of-freedom gyro compass for ship navigation, and two-degree-of-freedom gyros were used later as airplane orientation sensors. Schemes and components derived from these systems were applied to the first rocket attitude control systems. A somewhat more difficult task was to obtain guidance sensors, which did not exist yet. For many years inertial sensors were in competition with radio guidance devices, the latter being more promising in the early years to fulfill accuracy requirements. Accelerometers had to be used as inertial sensors for guidance. Velocity and displacement, as the information required, had to be derived; the first with normalized accuracy demands of at least 10~-10~ . The derived signals had to be obtained by the only available method, which was mechanical integration. In contrast to the inertial sensors, the radio sensors measured lateral displacements and forward (radial) velocities directly. Since the guidance systems had to be used for missiles an inertial system was preferable because it is self-contained and not subjected to external interference as radio guidance systems are. The radio guidance system became available and operational first. It yielded an accuracy in range that was about 10% better than the inertial system introduced afterward. Only a few test flights with a pure inertial system took place before the end of World War II. The cross-range impact errors were approximately twice as large as with the radio guidance system. Thus for some time it