A PASSIVE VARIABLE THERMAL RESISTANCE DEVICE IS PROPOSED WHICH UTILIZES A FLEXIBLE HEAT PIPE SWITCH.

A PASSIVE VARIABLE THERMAL RESISTANCE DEVICE IS PROPOSED WHICH UTILIZES A FLEXIBLE HEAT PIPE SWITCH. THE PRINCIPLE ELEMENT OF THE SWITCH IS A HEAT PIPE CHAMBER WITH A FLEXIBLEENVELOPE. THE SWITCH IS PERMANENTLY ATTACHED TO THE HEAT SOURCE. INCREASING SOURCE TEMPERATURE ELEVATES THE HEAT PIPETEMPERATURE AND PRESSURE, EXPANDING ITS ENVELOPE TO CONTACT THE SINK. DECREASING SOURCE TEMPERATURE CAUSES THE HEAT PIPE ENVELOPE TO CONTRACT, INTERRUPTINGCONDUCTIVE HEAT TRANSFER TO THE SINK. THE VARIABLE CONDUCT IVE PATH TO THE SINK ENABLES THE SWITCH TO MAINTAIN CONSTANTSOURCE TEMPERATURE OVER A WIDE RANGE OF HEAT LOAD AND/OR SINK CONDITIONS. PROOF-OF-PRINCIPLE HAS BEEN DEMONSTRATED IN A PREVIOUS NASA SPONSORED PROGRAM. INVESTIGATION OF DESIGN MODIFICATIONS TO ADAPT THE PRINCIPLE TO MEET THE DESIGN REQUIREMENTS OF A VARIABLE THERMAL RESISTANCE DEVICE IS PROPOSED. PHASE I OF THE PROPOSED EFFORT WILL CULMINATE IN THE DESIGN, FABRICATION AND TEST OF A PROTOTYPESWITCH IN A REPRESENTATIVE OPERATIONAL ENVIRONMENT.