Adaptable passive viscous damper: an adaptable D-StrutTM

This paper summarizes a development study that involved the design, fabrication, and test of a prototype adjustable viscous damper. The study, sponsored by NASA Langley Research, was performed by McDonnell Douglas and Honeywell, and addressed the need for an adaptable passive damping system for spacecraft by investigating methods of tuning the passive viscous damping device known as the D-StrutTM. The D-Strut is a flight-qualified device used for both compliant isolation systems and rigid structural damping systems. The goal of the study was to demonstrate a specific design that would allow peak damping to be adjustable between any frequency from 0.1 to 10 Hz. Several tuning methods were investigated. The tapered annulus concept was selected because it is mechanically simple and provides a broad range of damping adjustment. Results were predicted by modeling and design analyses. Characterization testing was performed using impedance test methods. High, low, and intermediate adjustments were made to validate range capability. Success of the project is clearly illustrated by impedance amplitude and phase plots.