Two-Phase Survivable Thermal Management - Heat Acquisition and Transport Components

This paper describes advanced heat acquisition and transport components developed and tested as part of the Two-Phase Survivable Thermal Management (TSTM) Program. The components are: a pumped heat pipe coldplate capable of removing very high-flux waste heat loads with a minimum temperature drop; and a thermal transport system designed to transport large quantities of waste heat over large distances with a long life and low power consumption. These components are intended for use in an advanced thermal control system which removes waste heat from high-power spacecraft.

For the heat acquisition component, a successful design development phase was completed, resulting in a producible design which met program goals. This design was subjected to extensive tests to demonstrate performance under a wide variety of conditions. The component was found to perform in a predictable manner. Measured overall component thermal conductance was 4.0 W/cm²/°C for fluxes up to 60 W/cm². The device was operated at steady-state heat fluxes up to 100 W/cm², and was subjected to brief pulse loads up to 200 W/cm².

For the heat transport component, existing pump and valve designs were substantially modified and a life test using ammonia working fluid was initiated. Design modifications were based on reliability requirements and prior ammonia loop experience. An ammonia life test flow loop was designed and constructed for the life tests. The ongoing tests have uncovered two design deficiencies in the centrifugal pump, which resulted in bearing degradation and failure. Design modifications were implemented, tests were resumed and the modified pump has been continuously operated for over 7500 hours without problems. The regulating valve has been continuously exposed to ammonia for over eighteen months and operated for over 7500 hours without any failures.