Dynamic Trap States of Dual-Spin Spacecraft

Two trap states are identified for spacecraft having asymmetric or unbalanced rotors. The first is a minimum energy state to which the spacecraft settles when the despin motor is deactivated. The second, encountered while despinning the platform, is characterized by a stalling of the despin process and a violent increase in nutation. Analysis demonstrates that, in both trap states, the spacecraft possesses two modes of attitude motion, each with a distinct frequency. Excitation by the motor at an appropriate natural frequency can lead to escape from either trap, even when the motor torque is insufficient to permit direct despin.