Dynamics of gyroelastic spacecraft

This paper introduces the concept of a gyroelastic spacecraft--a vehicle comprising not only a continuous distribution of mass and elasticity but a continuous distribution of gyricity (stored angular momentum) as well. It is assumed that the spacecraft has a number of gyroelastic appendages and that the (constrained) mode shapes are known for each of these appendages. General vehicle deformations are expanded in terms of these mode shapes. The eigenproblem for the (unconstrained) vehicle reveals a significant departure from the modal behavior of nongyric elastic vehicles. In particular, a gyroelastic vehicle can exhibit a "pseudorigid" mode in which the vehicle rotates uniformly in a deformed state. Although the frequency of this mode is zero, the associated strain energy is nonzero, and it is therefore not a "rigid" mode.