For spacecraft applications, energy storage sources are required to produce a high yield with minimum size and mass. Flywheel systems have the potential to fill this need while also providing attitude control for the guidance of the craft.Other advantages include on-board peak power management, extended service life (as compared to chemical batteries), and provisions for redundant systems with minimum effect on the projected payload of the craft. This paper reviews the results of flywheel design projects carried out at The University of Texas at Austin Center for Electromechanics (UT-CEM), discusses the role of composites in design development, and presents a detailed discussion of a flywheel design currently under study. INTRODUCTIONFlywheel systems are being designed for use in spacecraft because they offer significant advantages over chemical-based energy sources:

The University of Texas at Austin Center for Electromechanics (UT-CEM) is under contract to develop high-speed composite flywheel systems for a number of energy and power averaging applications in the transportation and space industries. Safe and reliable design of composite flywheels requires well-characterized material properties. Efforts have been focused on design optimization of a hydroburst test technique that demonstrates a useful method for characterizing the hoop (circumferential) properties of filament wound composite rings, and those results are then available to predict the performance of full-scale flywheels. To demonstrate the usefulness of this method, this paper discusses typical hydroburst techniques to determine material properties for filament-wound composite rings. Test results are also presented. Seal design is a key element of this fixture, and a design has evolved that provides nearly uniform radial loading on the inside surface of the composite ring, while minimizing axial bending. Correlations of tow strand data with hydroburst lamina data are presented. Also discussed are hydroburst test applications for flaw assessment and fatigue property evaluation.

Abstract--The University of Texas Center for Electromechanics (UT-CEM), as a member of the Defense Advanced Research Projects Agency (DARPA) Flywheel Safety and Containment program, has developed a lightweight containment system for high-speed, composite rotors. The containment device, consisting of a rotatable, composite structure has been demonstrated to contain the high-energy release from a rotor burst event and is applicable to composite rotors for pulsed power applications. UT-CEM recently conducted a burst spin test of a composite flywheel inside this composite containment device at Test Devices Incorporated (TDI) of Hudson MA. The most important aspect of this design is that the free-floating containment structure dissipates the major loads (radial, torque, and axial) encountered during the burst event, greatly reducing the loads that pass through the stator structure to its attachments. The design results in significant system-level weight savings for the entire rotating machine when compared to a system with an all-metallic containment. Of equal interest to the containment design, the experimental design and instrumentation was very challenging and resulted in significant lessons learned. This paper describes the containment system design, rotor burst test setup, instrumentation for measuring loads induced by the burst event, and a detailed explanation of the successful containment test results and conclusions.

-The maturation of pulsed rotating machines has evolved to the stage where a greater degree of basic research is required to further increase the energy and power density of advanced compulsators. The University of Texas at Austin Center for Electromechanics is studying the combined mechanical and electrical aspects of very high speed compulsator rotor designs for the next generation of compact pulsed rotating machines.This paper describes the design, construction, and testing of three scaled composite rotors. Performance specifications included hoop stresses of 1.7 GPa (250 ksi) in the outer banding and strain excursions of 0.4% in the field coil region. Results from the three studies are reviewed in detail. Techniques developed at the Center for Electromechanics for determining composite rotor performance are also discussed.

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