Embedded heat pipe assembly
Lancaster, PA

A Thermacore heat pipe assembly recently completed testing at the NASA Ames Arc Jet Complex, operating at very high temperatures in a hypersonic leading-edge simulation.

Developed in conjunction with the Lockheed Martin Company, the tested Thermacore module used six embedded heat pipes. Under independent tests, two units were operated in an arc jet plasma field at environments representing hypersonic conditions. The results were the same for both units, thereby demonstrating repeatability and reliability of the thermal protection system.

The Thermacore assembly is a rigid structure that absorbs heat at the leading edge, and then uses embedded heat pipes to spread the heat to larger surfaces, where it is radiated back to the atmosphere/environment.

A continuous electrical arc between two sets of electrodes exposed the heat pipe to assembly gases heated and expanded to very high temperatures and supersonic/hypersonic speeds. The gases — typically atmospheric air — passed through a nozzle aimed at the test sample in a vacuum. The flowing gases produced a reasonable approximation of the surface temperature and pressure, and the gas enthalpy found in high-velocity, supersonic flow — in this case, simulating high heat flux conditions at speeds from Mach 5 up to Mach 20.

The arc jet data has validated thermal models, heat shield design, and performance characteristics, including double containment of the working fluid. Full integration of the 15-centimeter-wide, 25-centimeter-deep module was accomplished within the static edge of the wing mounting structure. The module is ready for prototyping in an operational environment for spacecraft and hypersonic vehicles.

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