Cascaded Cryogenic Flexible Loop Heat Pipes (P12-2511)

Future spacecraft will require efficient heat transport at 60K Or lower, and will require flexible and thermal diode features. Cryogenic flexible heat pipes and capillary pumped loops have been developed, but are not capable of adverse tilt operation and rapid, autonomous startup. Loop heat pipes with advanced fine pore evaporator wicks show promise for meeting future needs, provided that rapid, autonomous startup can be achieved. It is proposed to develop a cascaded loop heat pipe that will operate autonomously between ambient and 65K in Phase 1. The Phase II work effort will extend the range of operation to between 15K and 25K. In Phase 1, a propylene loop heat pipe will be integrated with an oxygen or nitrogen loop heat pipe into a cascaded array for reliable, rapid startup. This approach has been demonstrated for conventional heat pipes but has not been explored for loop heat pipes. This device will function as a heat pipe continuously between 65K and 300K or greater and will operate as a thermal diode and provide a flexible transport section.