Flywheels to Provide Satellite Power and Attitude Control

May 02, 2006 by Jeff Shepard

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

"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 10 times as a traditional battery-based energy storage subsystem," said Dr. Brian Wilson, a Space Vehicles Directorate electrical engineer working on the experiment. "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."

For decades, rotational disks (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.

"I'm definitely looking forward to demonstrating the combined energy storage and attitude control capability of FACETS and showing the feasibility of something that has never been done before," said Dr. Jerry Fausz, FACETS program manager, AFRL's Space Vehicles Directorate.

Completed in February 2006, the mini-Agile Multi-Purpose Satellite Simulator (mini-

AMPSS) is a three-degree-of-freedom structure weighing over a 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. The FACETS contains a device, similar to a car alternator, which will convert rotational power into electricity to operate a spacecraft's payloads. To maintain a satellite's attitude control, the system will also possess the capability to change the flywheel speed and spin axis to point mini-AMPSS in a different direction.

"The FACETS experiment represents the first full-scale, three degree-of-freedom, mission-traceable, ground demonstration that introduces the Air Force to this new concept of combined energy storage and attitude control," said Dr. Wilson. "Our successful demonstration will mature the technology through its adolescence. The excitement generated by this groundbreaking demonstration could lead to a flight experiment, further maturing the FACETS system. These are the first steps necessary in the ultimate transition of the FACETS technology to military and commercial customers in the greater aerospace community."