Configuration 10 provided the best wear protection and least amount of visible wear debris of all  configurations tested. This conclusion is supported each and every aspect of the experimental data, that is: (1) excellent wear protection per qualitative assessment of the roller surface conditions; (2) low mass loss for both rollers, (3) wear depths were too small be detected by profilometer inspection. It is recommended that this configuration should be carefully considered for implementation including durability and performance evaluations of the mechanism subsystem in appropriate cold-vacuum conditions.  Summary After a qualification test of a mechanism for a space telescope, roller wear and particulate debris from  adhesive wear was noted. With intent to minimize wear and resulting debris, sets of experiments were  completed using a vacuum roller rig to mimic the mechanism contact conditions. Ten configurations were  tested. The roller-pair material configurations were evaluated on basis of qualitative assessment of roller  surface conditions, mass lost or gained by each roller, and wear phenomena as could be assessed by stylus profilometer and scanning-electron-microscope inspections. Specific findings were: 1. Changing the roller material from annealed 440F steel to 440C steel hardened to HRC 58-60 resulted in a reduction of overall wear by a factor of two to three. 2. Use of a polyimide roller instead of a steel roller is not suited for this application as the anodized  Ti6Al4V surface created polyimide debris in a manner like a machining process. 3. The bonded solid lubricant film that was applied to the steel roller was abraded and/or broke  down from the contact pressure. Large amounts of debris were created. 4. While diamond-like-carbon coatings altered the wear behavior, large amounts of debris were created. The investigated diamond-like-carbon coatings are not suited for this application. 5. Application of a nanocomposite MoS 2film significantly reduced the wear and production of wear  debris. 6. Application of the nanocomposite MoS 2film to both rollers provided better wear protection than providing the coating to the upper hardened 440C steel roller only. 7. Smoothing of the anodized Ti6Al4V prior to coating with the nanocomposite MoS 2film resulted in  better wear protection and the least amount of visible debris.  8. It is recommended that Configuration 10 should be carefully considered for implementation.  Configuration 10 is use of a nanocomposite MoS 2film sputtered on passivated 440C steel  hardened to HRC 58-60 and also sputtered on anodized Ti6Al4V that has been ultrasonically smoothed after anodizing and prior to sputtering. Acknowledgements This research was initiated and supported by the NASA Engineering Safety Center. The author thanks  the following for extended technical discussions, providing data and technical papers, and/or timely response in the processing of test rollers:  J. Zabinski Army Research Laboratory C. Beal Everlube Products Company M. Dugger Sandia National Laboratories S. Prasad Sandia National Laboratories G. Doll The University of Akron A. Korenyi-Both Tribologix Inc. Trade names and trademarks are used in this report for identification only. Their usage does not  constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space  Administration 100