Comparison of Grease and Solid Lubrication of Rolling Bearings Under Small-Stroke Reciprocation for Space Applications

Rotary actuator is a device responsible for the precise rotation of sensitive instruments such as antennas. Requirements for its precision and stiffness are extremely high. Actuators used in the space environment have to work for long period, under extreme condition and without possibility of repair or replacement. One of the main components responsible for its proper function are bearings. They precisely support shafts, and usually operate in a very small angular range with many repetitions. Selection of the proper bearing design and also the lubrication of the bearing can have significant effect on the performance and life of the entire satellite. Purpose of this study was to select and test suitable lubricant to support operation of such bearing. Sets of bearings lubricated by Rheolube 2000 and MoS2 PVD film were tested in thermal vacuum chamber under small angle oscillatory motion with the same start and end position for every cycle. Torque and bearing noise was evaluated during the tests and bearings were inspected. Rheolube 2000 was selected as the best lubricant for the described conditions because of the acceptable torque, lower bearing noise and easier manipulation during assembly and testing. However, both options proved to be applicable.