Extended Stroke and Miniaturized Reverse-Operation DTE Thermal Switches



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50th International Conference on Environmental Systems


This paper describes two advanced thermal switches under development at JPL that are offshoots of the recently flight-qualified 2500:1 reverse-operation differential thermal expansion (DTE) thermal switch (ROD-TSW). The first new device is the extended stroke ROD-TSW (or ES-ROD-TSW) while the second new device is the miniaturized ROD-TSW (or mini-ROD-TSW). ES-ROD-TSW development was funded by a NASA Center Innovation Fund (CIF) Advanced Concepts FY20 award to JPL, which is a joint project with NASA/MSFC, who was funded by their own FY20 NASA CIF award to participate in ES-ROD-TSW development. Mini-ROD-TSW development was funded by an internal JPL R&TD award in FY20. Each of these two new thermal switches employs multiple diametrically nested DTE stages in contrast to the original single-stage ROD-TSW. The ES-ROD-TSW employs two such stages as well as a novel negative CTE material known as Allvar and its main purpose is to extend the stroke of the ROD-TSW so that the gap when OFF is large enough (1 mm) for operation in non-vacuum planetary environments. The mini-ROD-TSW employs four such stages, and its main purpose is to miniaturize its size (2.54 cm envelope, 30 gram mass) for use in miniaturized lunar instruments and rovers. The ES-ROD-TSW was lab bench and TVAC tested at JPL and its ON/OFF ratio is 13000:1 based on a measured ON conductance of 6.89 W/K and a calculated OFF conductance of 0.00053 W/K. The measured OFF conductance of the ES-ROD-TSW of 0.003 W/K is likely erroneously high due to instrumentation limitations. The target performance for the mini-ROD-TSW was an ON conductance of 1.5 W/K and an OFF conductance of 0.0015 W/K, both of which were verified by analysis. Test verification of mini-ROD-TSW performance remains to be carried out. The paper will provide design and performance details of these two new advanced thermal switching devices.


David Bugby, Jet Propulsion Laboratory, California Institute of Technology
Jose Rivera, Jet Propulsion Laboratory, California Institute of Technology
Stephanie Mauro, NASA Marshall
Jeffery Farmer, NASA Marshall
ICES104: Advances in Thermal Control Technology
The 50th International Conference on Environmental Systems was held virtually on 12 July 2021 through 14 July 2021.


Thermal Management, Thermal Switching, Thermal Isolation, Extreme Environments, Thermal Toolbox, Differential Thermal Expansion