Power Electronics

Flywheel Stabilizers Power Satellites

By the summer of 2007, a team of eight personnel serving at the Air Force Research Laboratory’s Space Vehicles Directorate, Kirtland Air Force Base, N.M., believe their experiment consisting of three flywheels, spinning between 16,000 rpm and 40,000 rpm, will demonstrate the innovative technology of combined attitude control and energy storage on a satellite.

For decades, flywheels have been employed as spacecraft positioning devices, but have not extensively been considered for power purposes. The success of the Flywheel Attitude Control, Energy Transmission and Storage (FACETS) system’s unique trial could change that perspective.

Completed in February 2006, the mini-Agile Multi-Purpose Satellite Simulator (mini-AMPSS) is a three-degree-of-freedom structure weighing over one ton. Affixed on a pressurized air bearing, it serves as the testbed for the FACETS units, which will be mounted on it. Built under contract with Honeywell, the tri-flywheel arrangement will be used to store energy as momentum, supplying power through an electromagnetic drive system.

“FACETS system can point the satellite like traditional attitude control systems, and in addition, its flywheels can provide power to spacecraft payloads at levels as much as much as 10 times greater than a traditional battery-based energy storage subsystem” Dr. Wilson said. “The frictionless magnetic bearings employed in the flywheel energy storage subsystem give FACETS the ability to operate on-orbit for about twice as long as a satellite using chemical batteries.”

The FACETS program dates back to the late 1980s and early 1990s with the Strategic Defense Initiative (SDI). Advancing from a space-based laser concept developed under the SDI, the Advanced Structures Experiment (ASTREX) conducted at Edwards Air Force Base, Calif., was used by AFRL to test control of large space structures. In 1992, the initial experiments at Edwards Air Force Base ceased. Eventually, the dormant ASTREX structure moved to the Space Vehicles Directorate at Kirtland Air Force Base, N.M. By 1997, it would become the foundation for the FACETS concept.

FACETS has the potential to benefit the Space Radar system. Meeting the high power levels required when the radar is operational demands significant over-sizing of the chemical batteries, which can only deliver a limited amount of power. Once the radar is inactive, the oversized batteries represent excess weight. On the other hand, flywheel systems can be designed to handle the very high peak power needs without the requirement of being oversized. They are uniquely effective at providing sudden, large amounts of power, but are not a detriment during low power mission phases. The net result is dramatically reduced combined energy storage and attitude control system weight.

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