Extended Stroke and Miniaturized Reverse-Operation DTE Thermal Switches

This paper describes two advanced thermal switches under development that are offshoots of the recently flight-qualified 2500:1 reverse-operation differential thermal expansion (DTE) thermal switch (ROD-TSW). The first is the extended stroke ROD-TSW (ES-ROD-TSW) while the second is the miniaturized ROD-TSW (mini-ROD-TSW). Each employs multiple diametrically nested DTE stages in contrast to the single-stage ROD-TSW. The ES-ROD-TSW employs two stages and a negative CTE material known as Allvar and its main purpose is to extend its stroke for use in non-vacuum planetary environments. The mini-ROD-TSW employs four stages to miniaturize its size for use in compact lunar instruments and rovers. The ES-ROD-TSW was 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 mini-ROD-TSW is targeted to have an ON conductance of 1.5 W/K and an OFF conductance of 0.0015 W/K, both verified by analysis. Test verification of the mini-ROD-TSW remains to be carried out. The paper will provide design/performance details of each device.