Application of collar seals for bearings in the lunar exploration rover

Abstract

A lot of exploration missions have been planned for the moon, and lunar activity is likely to increase. The moon’s surface is covered by a great deal of dust, called regolith, and these particles can seriously damage mechanical components. The design of any mechanism that will operate on the moon must take regolith into account. This includes the wheels and crawlers of lunar rovers, and many other mechanical components. This study considers measures for protecting small bearings in a lunar rover that operate close to the surface, in particular simple collar seals. These seals will require exceptional sealing ability, low torque, light weight, and easy installation. Collar seals made of three polymer composite materials (such as PTFE and PEEK) were evaluated. The seals have a convex portion that slides on the end face of the inner ring of a bearing or that of the outer ring; the sliding between the convex portion and the rings prevents regolith from entering the bearing. The seal performance and torque of each type of collar seal were tested using a regolith simulant in vacuum. The test conditions were decided based on the lunar environment and specification of a lunar rover under development. In order to maintain seal performance and to obtain lower torque, the thicknesses of the collar seals and their axial deflection were varied. Sliding on the end face of the inner ring of the bearing showed good seal performance and lower torque with optimum collar thickness and axial deflection for all composite materials. There was some variation in sealing and torque between the composites. The tribological performance and results of surface analysis by XPS are discussed.