<h2>AAS  96-159</h2><h2>NONLINEAR INSTABILITIES IN A DUAL-SPIN SPACECRAFT WITH AN AXIAL NUTATIONAL DAMPER</h2><h4>P. A. Meehan and S. F. Asokanthan, University of Queensland</h4><h2> Abstract </h2>The dynamics of a dual-spin spacecraft with an axial nutational damper is investigated for non-linear phenomena.  The system is found to exhibit chaotic motion when a sinusoidally varying torque is applied to the spacecraft rotor.  A similar situation, in practice, may arise during spin-up of an unbalanced rotor.  The motion is studied using various methods such as bifurcation diagrams, Lyapunov characteristic exponents and Correlation Dimension.  Predicted instabilities indicate the range of rotor speeds and perturbation amplitudes to be avoided.  Onset of chaotic motion was shown to be characterised by period doubling and Hopf bifurcations.<br><br>