Attitude control of large solar power satellites

Satellite power systems are a promising future source of electrical energy. However, the very large size solar power satellites (relative to contemporary spacecraft) requires investigation of the resulting attitude control problems and of appropriate control techniques. The principal effects of the large size are a great increase in sensitivity to gravity-gradient torques and a great reduction in structural bending frequencies with the attendant likelihood of undesirable control system interaction. A wide variety of control techniques are investigated to define approaches that minimize implementation penalties. These techniques include space-constructed momentum wheels, gravity-gradient stabilization, quasi-inertial free-drift modes, and various reaction control thruster types, some of which reduce the implementation penalties to a few percent of the spacecraft mass. The control system/structural dynamic interaction problem is found to have a tractable solution. Some of the results can be applied to other large space structure spacecraft.