Design and Optimization of a Test Setup for Low Thermal Conductance Measurements

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2023 International Conference on Environmental Systems

Bearings are essential to rotational spacecraft components so a proper understanding of bearing behavior is necessary for reliable spacecraft operation. Characterization of bearing thermal conductance provides accurate temperature predictions, which are important to a successful design so that critical mechanical fit is maintained, and lubricant degradation and migration is avoided. The Aerospace Corporation's Bearing Thermal Test facility has provided valuable bearing conductance data, but its test method has proven to be complex and takes multiple months to complete. A static "Ball-on-Flat" test is being developed to simplify bearing conductance testing, specifically for low-speed bearings where dynamic effects are not considered. This test consists of a single, lubricated ball between two "flats." Two heat flux meters with embedded thermocouples capture the thermal gradient across the experiment, which is used to calculate the conductance across the ball and two flats. These test results are used to characterize the conductance of a complete bearing with a correlation factor determined by Aerospace's BBTherm tool. Initial path finding tests showed that the measurements have high uncertainty because the low thermal conductance of the ball causes the setup to be insulative, with very little temperature differences between thermocouple readings. This paper describes the use of regression analysis and Kuhn-Tucker necessary conditions to optimize the heat flux meter dimensions and thermocouple spacing to reduce the measured conductance uncertainty. The use of uncertainty analysis in the experimental design will allow the test to provide agile and accurate thermal characterization of various ball and lubricant combinations.

Natalie Walsh,
Christopher Ye,
Christopher Bertagne,
Yoshimi Takeuchi,
John McHale,
ICES511: Reliability for Space Based Systems
The 52nd International Conference on Environmental Systems was held in Calgary, Canada, on 16 July 2023 through 20 July 2023.
bearing, ball bearing, rotational spacecraft component, thermal conductance characterization, uncertainty based experimental design, agile thermal characterization