© 2018 Sierra Nevada Corporation Conclusions  Developmental testing to inform design decisions and provide confidence in qualification life was  successfully completed. These developmental tests were not intended to address all possible operational  variables, but were specifically targeted to the mission parameters of these Mars 2020 gearbox designs.  Several other observations, conclusions, and areas for future work were recorded as a result of this  developmental testing:  •If necessary and financially feasible, a parallel path of procurement different design options while awaiting developmental test results can preserve accelerated program schedules by allowing final design decisions to be informed by those test results. •PFPE-family lubricants may have successful use for short durations at higher Hertzian contact stresses than previously published. Testing of mission-specific operational characteristics is recommended. •The extremely cold operating temperatures for Mars mechanisms are particularly challenging for wet lubrication schemes since operation at temperatures near the lubricant pour point may result in poor lubricant mobility, leading to starvation and insufficient protection of wear surfaces, especially for porous bushings. •While bushings lubricated with either oil completed testing successfully in the flight-like gearbox, bushings lubricated with Brayco 814 oil exhibited less wear than those lubricated with Brayco 815Z oil in SNC’s development testing, likely due the lower viscosity of Brayco 814 oil at cold temperatures. •Every effort should be made to scrutinize test fixtures and test components in the most flightrepresentative configuration possible to prevent false failures, as was believed to have occurred in the component-level bushing test. Acknowledgements  This work was funded by JPL under Subcontract 1541135. The authors wish to express appreciation to  the Motion Control Subsystem (MCS) team at JPL for their collaboration in the preparation and review of  these developmental tests.  References  1. Conley, P.L. and Bohner, J.J., “Experience with Synthetic Fluorinated Fluid Lubricants”, Proc. 24th Aerospace Mech. Symp., NASA CP-3062, Kennedy Space Center, FL (1990) 2. Mobley, J.D. et al., “Extended Life Testing of Duplex Ball Bearings”, Proc. 43rd Aerospace Mech. Symp., NASA CP-2016-219090, Santa Clara, CA (2016) 3 . Lo, C.J., et al., “Use of Cumulative Degradation Factor Prediction and Life Test Result of the Thruster Gimbal Assembly Actuator for the Dawn Flight Project”, NASA CR-2009-215681 4. Mobley, J.D., “Trade Studies for a High Torque Density Planetary Gearbox”, Proc. 41st Aerospace Mech. Symp.,  NASA CP-2012-217653, Pasadena, CA (2012) 5.Materials Standards for PM Self-Lubricating Bearings . Metal Powder Industries Federation, 2010. MPIF Standard 35 6. Herman, J. and Davis, K., “Evaluation of Perfluoropolyether Lubricant Lifetime in the High Stress and High Stress-Cycle Regime for Mars Applications”, Proc. 39th Aerospace Mech. Symp., NASA CP2008-215252, Huntsville, AL (2008) 7. Castrol. Brayco Micronic 814 Product Datasheet, Castrol, 2009, https://thelubricantoracle.castrol.com/product/brayco-micronic-814/alternatives/industrial/en-JP 8. Castrol. Brayco Micronic 815 Z Product Datasheet, Castrol, 2009, thelubricantoracle.castrol.com/product/brayco-micronic-815-z/industrial/en-JP 9.Design Manual for Enclosed Epicyclic Gear Drives . American Gear Manufacturers Association, 2006. ANSI/AGMA 6123-B06 NASA/CP—2018-219887 541