Touchdown/Launch-Lock Mechanism for Magnetically Suspended Control Moment Gyroscope

In the event of power failure in a magnetically suspended Control Moment Gyroscope (CMG), a mechanical touchdown bearing is required to prevent contact between the rotor and various magnetic actuators. Additionally, a launch-lock system must be provided to suspend the rotor during launch, when power is not applied to the CMG. Honeywell Inc. has incorporated both of these functions into one system. This paper describes the patented system, including pertinent design details, and summarizes bench- and brass-board CMG testing results. Described in design information is an essential aspect of the bearing design, a conical clutch that acts as both contact interface and launch-lock mechanism. Test results summarize materials used for critical interface between the touchdown system and rotor, as well as results of durability tests (1000 touchdowns at various loads) in a bench test rig, and planned and unplanned touchdowns in the CMG test bed. Predominant lessons learned include the discovery of: At least one successful material combination for high-speed, high-load contact. The affect of lubrication on contact interfaces. How grease lubricated bearings work at very high acceleration rates to speeds up to 1.1 x 106 DN. Unexpected reasons for over designing bearing load capacities, for this type of application.