Spinrac, AN Attitude Control System for Obtaining Low Impact Dispersion

The Spining Rocket Attitude Control system, (SPINRAC) system for three-stage sounding rocket impact dispersion reduction is described. The SPINRAC points the spin-stabilized third stage to a predetermined attitude, prior to ignition. The SPINRAC uses a roll-stabilized gyro platform for inertial attitude information, processes the signals in a microcomputer, and uses a cold-gas system for actuation. Using control theory the guidance time can be kept small and thrust force low. Typically a reorientation angle of 20 deg and a coning half-angle of 10 deg is controlled to an accuracy of 0.4 deg 3-sigma value within 20 sec. Using the SPINRAC on a three-stage sounding rocket (Black Brant X, Skylark 12) makes it possible to reach apogee altitudes of 1000 km while maintaining low impact dispersion.