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Bonding Issue Almost Endangers Delivery Date of Panel: Part II
09.24.2009 9:41 AM
Ruwan Somawardhana

By Ruwan Somawardhana
Spacecraft Thermal Engineering

As a follow-up to my previous entry regarding the bonding issues of the thermal spreader, I was able to complete a Thermal Math Model (TMM) to verify my hand calculations. The TMM results confirmed that even with a “dry” mount, meaning there was no bond material and only conductance due to the mechanical fasteners were used, there was sufficient thermal margin that the electronics boxes would not violate their AFT requirements. However, by having a good “wet” interface, meaning a uniformly filled gap with an interstitial material, the temperature of one of the critical pieces of hardware could be reduced by approximately 10°C. A cooler temperature for this particular piece of hardware correlates with improved performance return.

A review was conducted with the manufacturer, various experts from JPL, and the cognizant engineers for the hardware subsystem on how to proceed. The final decision was to remove the old thermal spreader and re-bond it using a new technique to try and get a uniform “wet” interface. The removal and mounting of the new thermal spreader has now been completed and the new process seems to have successfully worked. Sometime in the future, this panel is scheduled to be thermally tested in a vacuum chamber and it will be interesting to see the true performance .


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