A heat pipe furnace developement, funded by the European Space Agency (ESA), was carried out to demonstrate the potential of the heat pipe heating technique at temperatures up to 1500°C for future material processing purposes and for process temperature control in a microgravity environment. The furnace consists of a constant conductance heat pipe made of molybdenum 41 wt% rhenium and employs lithium as the working fluid. Special provisions are made allowing indirect heat pipe temperature measurement via working fluid vapour pressure measurement.
The heat pipe furnace was successfully operated in the temperature range from 900°C to 1500°C for a total of more than 150 hours. The tests showed the applicability of the in-indirect temperature measurement technique via vapour pressure measurement even for heat pipe temperatures far above normally permissible temperatures of commercially available pressure sensors.