ZERO-RESIDUAL-ENERGY, SINGLE-AXIS SLEW OF FLEXIBLE SPACECRAFT USING THRUSTERS - DYNAMICS APPROACH

By examining the phase plane response of an elastic mode to a sequence of step torques, the paper first shows that if the half-slew time is an integer times the modal period, a flexible spacecraft can be slewed with zero residual energy in one critical mode. Because this stipulation cannot be met for an arbitrary slew angle and slew acceleration, two intervening pulses of equal width for undamped mode, and of unequal width for damped mode, are shown to be required to achieve two goals at once: 1) slew the spacecraft by the desired angle, and 2) have zero residual energy in a critical elastic mode. Using elementary structural dynamics, easily solvable analytical relationships are developed among the rest-to-rest maneuver angle, slew acceleration, slew time, widths of the intervening pulses, natural frequency of the critical mode, and its damping coefficient. This minimum-time, zero-residual-energy, single-axis slew is illustrated on a spacecraft with two solar arrays. In addition, the assumption of only one elastic mode being critical is carefully examined. To bring cohesion between this work and the works in the past, the place of this contribution is identified. Finally, to bring an arbitrary rigid and elastic modal state of a flexible spacecraft to the origin, a conceptual, discrete control scheme using thrusters is suggested.