The paper deals with dynamics of a specific gyroscopic flexible spacecraft and with synthesis of its controller. The infinite number of associated gyroscopic modes are shown to have alternately a precession parallel and antiparallel to the stored momentum. Dependence of mode shapes on the rotor's momentum is investigated. Identities based on the vehicle's momentum and inertia considerations are devised. The stochastic response of the spacecraft subject to arbitrary permits a modal cost analysis of the vehicle. These developments show that, as rotor's momentum escalates, a larger number of modes are required to construct a truncated model having a prespecified accuracy. A controller is designed on the basis of the minimum error excitation approach, which is found to be almost as effective as an optimal state feedback controller. The destabilizing influence of the truncated modes is exposed by utilizing the robustness inequalities available in the literature.