Application of synthetic gear wheels to space mechanisms

The goal of this work was to evaluate the wear behavior of PEEK gear wheels in a simulated space environment and their applicability in space mechanisms. With that study the question shall be answered if, despite a possible increased of the wear rate of a PEEK pinion, the accuracy requirements of a pointing mechanism can still be met. Polyetheretherketone (PEEK) is a promising material for the manufacturing of gear wheels in space applications. PEEK has high strength, high wear resistance, good behavior at extreme temperatures, and a low outgassing rate. But what makes PEEK particularly interesting for the application in space mechanisms is its ability to be used without lubrication. A back-to-back gear test rig was developed in order to conduct the wear tests of a pinion made out of PEEK in a thermalvacuum chamber. The wear tests were run in four different environments: (1) ambient lab environment, (2) vacuum at room temperature, (3) vacuum at +80°C, and (4) vacuum at -55°C. Before and after each test the contour of selected teeth were measured and, with the area difference, the wear coefficient was determined and the theoretical increase of backlash was calculated. The results show a dependency of the wear rate as a function of the test environment. The lowest wear coefficient was observed in vacuum conditions at -55°C. The largest in vacuum at 80°C. But despite the wear-caused increase in backlash, the accuracy requirements of many pointing mechanisms can still be met.