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This paper outlines a manufacturing analysis of a composite flywheel that can then be manufactured, assembled, balanced, and integrated with a magnetically suspended system test apparatus, for use in an inertial energy storage system. The preferred flywheel geometry was found to be a constant thickness disk with a hole in the center, having an inside to outside diameter ratio of 0.45. On the basis of the detailed stress analysis performed, the usable stored energy density of the interference assembled flywheel is 65 Watt - hour/kg, when operating over a speed range of 37.5% to 75% of maximum speed. The preferred flywheel fabrication method is wet filament winding, with high strength carbon fibers, in an epoxy matrix. These fibers are arranged in the hoop direction. A composite material test program was designed to validate the required performance of the, composite material.

In low earth orbit satellite applications, spacecraft power is provided by photovoltaic cells and batteries. Unfortunately, use of batteries present difficulties due to their poor energy density, limited cycle lifetimes, reliability problems, and the difficulty in measuring the state of charge. Flywheel energy storage offers a viable alternative to overcome some of the limitations presented by batteries. FARE, Inc. has built a 50 Wh flywheel energy storage system. This system, called the Open Core Flywheel, is intended to be a prototype energy storage device for low earth orbit satellite applications. To date, the Open Core Flywheel has achieved a rotational speed of 26 krpm under digital control.